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Spatiotemporal patterns of salt and nutrient contamination in Los Angeles County's groundwater basins

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Spatiotemporal patterns of salt and nutrient contamination in Los Angeles County's groundwater basins

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SPATIOTEMPORAL PATTERNS OF SALT AND NUTRIENT CONTAMINATION
IN LOS ANGELES COUNTY’S GROUNDWATER BASINS

by

Holly Marie MacGillivray

A Thesis Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(GEOGRAPHIC INFORMATION SCIENCE AND TECHNOLOGY)

August 2012

Copyright 2012 Holly Marie MacGillivray
ii
Acknowledgements
I would like to thank my advisor Dr. John P. Wilson for his guidance, patience
and expert advice throughout this thesis project. I would also like to thank the members
of my thesis committee: Professors Karen Kemp and Jordan Hastings. Additionally, I
want to thank my academic advisor, Katherine Kelsey for help guiding me through the
process of completing a Masters Thesis.
I want to thank Elizabeth Erickson for her assistance in understanding the goals of
the Los Angeles Regional Water Quality Control Board’s Salt and Nutrient Management
plan. I want to thank my family and friends for their love and support while I worked to
complete my graduate studies. And lastly I would also like to thank Scott Freeman for
teaching me how to filter data with SAS software and for providing his constant love and
support.

iii
Table of Contents
Acknowledgements ii

List of Tables iv

Table of Figures v

Abstract vi

Chapter 1 – Introduction 1

1.1 Groundwater and Sources of Contamination 1

1.2 Groundwater Investigations and Geographic Information Systems 4

1.3 Purpose of this Thesis 5

1.4 Thesis Organization 6

Chapter 2 – Past Work 7

2.1 National and State Groundwater Contamination Studies 7

2.2 County and Local Groundwater Contamination Studies 9

2.3 Groundwater Contamination in California 12

Chapter 3 - Data and Methods 15

3.1 Study Area 15

3.2 Groundwater Data Collection and Management 22

3.3 Methods of Analysis 26

Chapter 4 - Results and Discussion 29

4.1 Groundwater Spatiotemporal Analysis 29

4.1.1 Salt Constituents 29

4.1.2 Nutrient Constituents 43

4.2 Additional Groundwater Spatial Analyses 50

Chapter 5 – Conclusions 57

5.1 Groundwater Quality in Los Angeles County 57

5.2 Limitations of the Spatiotemporal Analysis 60

5.3 Recommendations for Future Research 61

References 63

iv
List of Tables
Table 1: Summary of notable Los Angeles County groundwater
contamination studies. 13

Table 2: Groundwater constituent limits (in mg/L) by groundwater basin
(California Regional Water Control Board, 1994). 22

Table 3: Changes in constituent statistics following data removal as directed
in the text. 25

Table 4: The number and fractions of boron samples exceeding the respective
Basin Plan limits, in each basin, during each season. 30

Table 5: The number and fractions of chloride samples exceeding the
respective Basin Plan limits, in each basin, during each season. 32

Table 6: The number and fractions of sulfate samples exceeding the
respective Basin Plan limits, in each basin, during each season. 36

Table 7: The number and fractions of TDS samples exceeding the respective
Basin Plan limits, in each basin, during each season. 39

Table 8: The number and fractions of nitrite-nitrogen samples exceeding the
Basin Plan limit, in each basin, during each season. 44

Table 9: The number and fractions of nitrate samples exceeding the Basin
Plan limit, in each basin, during each season. 46

Table 10: The number and fractions of nitrate-nitrogen samples exceeding the
Basin Plan limit, in each basin, during each season. 48

Table 11: The number and fractions of samples exceeding the respective
Basin Plan limits for each constituent at each equal sampled depth. 51

Table 12: The numbers and fractions of samples exceeding the respective
Basin Plan limits for each salt constituent at various distances from
the coastline. 55

v
Table of Figures
Figure 1: Los Angeles County’s groundwater basins. 19

Figure 2: Maps showing clusters of samples that dominate the Geotracker
dataset. 27

Figure 3: The percentage of chloride samples exceeding the respective Basin
Plan limits, during each season, in the seven analyzed basins. 31

Figure 4: Spatial distribution of chloride samples in the Hollywood basin,
during each season. 34

Figure 5: The percentage of sulfate samples exceeding the respective Basin
Plan limits, during each season, in the eight analyzed basins. 35

Figure 6: Spatial distribution of sulfate samples in the San Gabriel basin,
during each season. 38

Figure 7: The percentage of TDS samples exceeding the respective Basin
Plan limits, during each season, in the seven analyzed basins. 40

Figure 8: Spatial distribution of TDS samples in the Central basin, during
each season. 42

Figure 9: The percentage of nitrate-nitrogen samples exceeding the Basin
Plan limit, during each season, in the eight analyzed basins. 49

Figure 10: The spatial distribution of nitrate-nitrogen samples in each of the
five depth classes. 53

Figure 11: The spatial distribution of sulfate samples in each of the five depth
classes. 54

vi
Abstract
Salts and nutrients are common contaminants in urban groundwater systems, and
at certain levels these pollutants have been associated with adverse effects on agriculture,
corrosion and mineral deposits on industrial piping, a decrease in the drinkability of
water, and serious health problems. Groundwater pollution can stem from both natural
and anthropogenic sources and given the high costs of remediation, groundwater
managers are tasked with monitoring groundwater contamination and controlling its
sources. With its large population, close proximity to the coastline and arid climate, Los
Angeles County provides an important study area for the spatial and temporal analysis of
salt and nutrient constituents across each of its 10 groundwater basins.
This thesis study utilizes the California Regional Water Quality Control Board
data set consisting of groundwater quality samples drawn from underground storage
tanks, site clean-up programs and land disposal sites to determine the spatiotemporal
patterns across each basin. Results show that no spatiotemporal pattern was recognized,
except that the salt constituents routinely exceeded the respective Basin Plan limits
(unlike the nutrient constituents). In the end, more conclusive results could be
determined with additional analysis and modeling that was better designed for sample
collection and better controlled over the locations and depths at which the samples were
taken.
1
Chapter 1 – Introduction
1.1 Groundwater and Sources of Contamination
Groundwater provides an important source of drinking water throughout the
world. One half of the drinking water and 40% of the irrigation water used in the U.S.
come from groundwater supplies (Corwin et al., 1997). However, multiple substances
can contaminate groundwater leaving it unfit for human consumption. In 1993, the U.S.
Environmental Protection Agency identified more than 200 chemical compounds present
in groundwater, many of which negatively impact the quality (Ducci, 1999). Salts and
nutrients are common contaminants in groundwater pollution. Excessive levels of salt in
groundwater can create adverse effects for agriculture, corrosion and mineral deposits on
industrial piping, and decrease the drinkability of water (Matsumoto, 2010). Excessive
nutrients have been linked to serious health problems including low oxygen levels in the
blood stream of infants, known as methemoglobinemia (Gardner and Vogel, 2005;
Hudak, 1999, 2000; Hudak and Sanmanee, 2003; Lee et al., 2006; Masetti et al., 2008;
Nolan et al., 1997, 2002; Pacheco and Cabrera, 1997), an increased risk of non-
Hodgkin’s lymphoma (Gardner and Vogel, 2005; Hudak, 1999, 2000; Hudak and
Sanmanee, 2003; Masetti et al., 2008; Nolan et al., 1997, 2002; Strebel et al., 1989), and
increased cancer risk through production of N-nitroso compounds in the body (Nolan et
al., 2002; Pacheco and Cabrera, 1997; Strebel et al., 1989).
Salt and nutrient pollution in groundwater has been attributed to both natural and
anthropogenic sources. Salts, such as sulfate and chloride, are naturally present in
evaporite minerals: sulfate, anhydrite, and halite, as well as in sedimentary rocks that
2
contained seawater during deposition (Hudak and Sanmanee, 2003). Salts also occur
naturally through seawater intrusion and salinization in arid regions (Uliana, 2005).
Nutrients are found naturally from weathering of nitrogen-bearing rocks, degradation of
organic matter in soils and atmospheric deposition (Böhlke, 2002). Natural
characteristics of soils and sedimentary layers also increase the ability for anthropogenic
sources to contaminate groundwater. Unconfined aquifers combined with shallow water
tables and coarse-grained, highly permeable unsaturated zones (Hudak, 1999; Nolan et
al., 1997) provide conditions that favor salts and nutrients at the surface percolating
through the soil to the groundwater table.
Anthropogenic sources of salt and nutrient pollution are numerous. Land use has
a direct influence on the quality of groundwater because of the types of chemicals that
can be introduced at the surface (Eckhardt and Stackelberg, 1995). Residential,
municipal, commercial, industrial and agricultural activities all have the ability to harm
groundwater quality (Nas and Berktay, 2010). Salts are contributed to groundwater from
sources such as agricultural fertilizers and other chemicals, oil field brine, sewage,
landfill leaching, industrial effluent and deicing salts from roadways (Hadak and
Sanmanee, 2003). Nutrients are contributed to the environment through crop and lawn
fertilizer, animal manure, septic systems (Hudak and Sanmanee, 2003), and the
combustion of fossil fuels, which increases the levels of atmospheric nitrogen deposition
(Puckett, 1994). Groundwater contamination can also be driven by human interaction
with the groundwater table. Over pumping groundwater from deep aquifers can
accelerate the movement of contaminants through the aquifer system (Kehew et al.,
3
1996). Pumping can also increase the levels of salt water intrusion that occurs in
groundwater basins near the coastline.
Point sources of pollution, such as sewage pipes and leaking septic tanks, provide
a straightforward target for monitoring and regulation. These sites have attracted the
attention of groundwater resource managers as they have worked to identify and contain
highly toxic concentrations of salts and nutrients that pose an immediate threat to human
health (Corwin et al., 1997). Nonpoint source pollutants, such as fertilizers, deicing salt
and road runoff, are dangerous because their contaminant contributions are more difficult
to limit and monitor. While these sources provide smaller concentrations of pollutants,
their accumulation through time may persist over several years or decades (Corwin et al.,
1997). Nonpoint source pollutants provide a different challenge to groundwater
managers because they do not respect political boundaries (Corwin et al., 1997), leading
to an increased need for a unified approach to monitoring and regulation.
Groundwater remediation is a costly, difficult, and slow process. The possible
remediation strategies include excavation, surface capping, subsurface barriers, and
chemical and biological treatment, among others (Ahn and Chon, 1999). With a strong
dependence on groundwater aquifers for potable water, identifying areas where
groundwater is at risk for contamination is an important and valuable step in managing
and protecting this natural resource (Masetti et al., 2008; Tesoriero and Voss, 1997;
Wilson et al., 1993). Oenema et al. (1998) examined the efficiency of policies the
Netherlands imposed for nitrate and phosphorus management for farmers, requiring
reports of all incoming and outgoing nutrients in imported and exported products on an
4
annual basis. The management strategies recommended in this study were expected to
lower the nitrate concentration from 40% in 1985 to 12% by 2037, although the authors
believed that additional policies would be necessary in areas of high concern.
1.2 Groundwater Investigations and Geographic Information Systems
Groundwater quality studies are of interest to governments and management
agencies, to help direct and fortify their policy decisions, as well as for university
researchers, looking to document changes in groundwater quality while seeking to
understand the sources of these pollutants. The latter is a substantial challenge because
the various stocks and flows that characterize the natural hydrology cycle vary
tremendously over space and time, and human modification of these systems more often
than not adds to this complexity.
These complexities have led to numerous approaches for examining groundwater
pollution and their sources. Studies have been conducted at different scales to uncover
varying extents of groundwater pollution. While state (e.g. Navulur and Engel, 1997)
and national scale (e.g. Nolan et al., 1997; Puckett, 1994) investigations are important for
highlighting the global patterns of pollution and their sources, there are multiple variables
that are site dependent and localized studies are recommended for developing support of
individual groundwater management decisions (Nolan et al., 2002). Groundwater
investigations set out to accomplish various goals, including the determination of sources
of pollution, predicting the areas that are vulnerable to pollution, and measuring the
spatial and temporal trends of the pollution.
5
Geographic Information Systems (GIS) have provided a new and useful means of
supporting groundwater quality investigations. GIS provides suites of software tools that
combine database management with digital mapping and analysis capabilities for
spatially-oriented data (Fritch et al., 2000). There are many advantages of GIS for
environmental monitoring, including groundwater analysis, advanced cartographic
abilities, the capacity to organize and synthesize large amounts of data for spatial
examination, and the capability to discover and display spatial relationships using
specialized empirical and statistical models (Corwin et al., 1997). The utilization of GIS
with a groundwater monitoring investigation allows the analyst to investigate the
different outcomes using several models with numerous datasets across various scales
(e.g. Araghinejad and Burn, 2005; Corwin et al., 1997; Goovaerts et al., 2005). The
coupling of groundwater analysis with GIS increases the speed and ease in which results
can be attained and conclusions can be drawn, enabling the ability to analyze larger
datasets with more complicated models across larger spatial extents.
1.3 Purpose of this Thesis
This thesis study was designed to complement the development of salt and
nutrient management plans by the Los Angeles Regional Water Quality Control Board,
the agency responsible for designating specific standards for groundwater quality in Los
Angeles and Ventura Counties. The purpose of this groundwater quality investigation is
to characterize the spatial and temporal patterns of salt and nutrient groundwater quality
in the 10 groundwater basins in Los Angeles County, California. In addition, the
variables of depth to groundwater and the distance to the coastline are examined to
6
determine the correlation of either variable with an increase in groundwater pollution in
any of the 10 basins.
1.4 Thesis Organization
The remainder of the thesis contains four chapters. Chapter 2 summarizes prior
work characterizing groundwater quality across a variety of natural and built
environmental settings. Chapter 3 discusses the data and methodology used for this
groundwater quality study. The study area, the methods of data collection, management
and analysis are described in detail. Chapter 4 presents and discusses the results of the
groundwater study, including maps of the spatial extent of pollution and the temporal
patterns uncovered. Chapter 5 presents the conclusions that can be drawn from the
analysis and proposes areas of further research.
7
Chapter 2 – Past Work
2.1 National and State Groundwater Contamination Studies
Small scale groundwater contamination studies provide an important
understanding of the broader context of groundwater quality. These studies are
conducted on national (e.g. Lake et al., 2003; Oenema et al., 1998, Puckett, 1994) and
state (Ceplecha et al., 2004) scales. Small scale groundwater quality studies look at very
broad datasets that require wide coverage with uniform data standards, often only
available in the form of state or national published datasets. With these data sources,
small scale groundwater quality studies typically utilize overlay and regression methods
for their analysis to determine the extent of high groundwater pollution, or areas highly
vulnerable to groundwater pollution.
Nolan et al. (1997), for example, produced a national nitrogen vulnerability map
of the U.S. The map was created by overlaying national datasets including nitrogen
loading and population density, as the nitrogen input variables, and soil drainage
characteristics and woodland to cropland ratio, as the aquifer vulnerability input
variables. The resulting map displayed areas with the combination of high and low
nitrogen loading with high and low aquifer vulnerability. The largest areas identified as
high vulnerability and high nitrogen loading were found in the Midwest, including
Nebraska, Kansas, Iowa, northern Illinois, southern Wisconsin and western Michigan, in
addition to central California, eastern Washington and southeast Pennsylvania.
Additionally, areas with high vulnerability, regardless of nitrogen loading levels, can be
utilized to identify where monitoring of groundwater pollution should occur. Nolan et
8
al. (2002) utilized regression modeling to predict nitrate contamination in shallow
groundwater across the U.S. The regression model used national datasets for nitrogen
loading, percent cropland, human population density, percent of well drained soils, depth
to groundwater and presence of a fracture zone in the underlying aquifer. The resulting
regression model was found to be well-correlated with observed groundwater data and
depicted high probability areas in the High Plains of the Midwest, the central California
basin, southeastern Washington and western Texas, all areas with extensive agricultural
operations.
State scale groundwater contamination studies typically offer more detailed
assessments of contamination. Hudak (2000), for example, conducted a state wide
groundwater quality study of Texas, utilizing 7,793 wells from the Texas Water
Department Board database to compile, map and evaluate regional patterns of nitrate
using GIS spatial analysis. The study determined the percentage of polluted wells in each
county, as well as the statistical correlation between nitrate concentration and well depth,
total area fertilized, and market value of livestock. While the latter two variables were
not found to be significant, there was a statistically significant inverse-correlation
between concentration and well depth.
National and state scale studies provide an important view of the groundwater
quality as a whole, identifying regional issues and characterizing groundwater pollution
patterns. Policy makers and monitoring agencies can utilize small scale maps in order to
better identify areas where localized groundwater studies would be appropriate as well as
the areas to distribute funding for such studies. However, small scale studies ignore the
9
contributions of local variables since they are not significant on the national scale,
causing the study results to be inappropriate for local management to utilize for
supporting decisions (Nolan et al., 2002).
2.2 County and Local Groundwater Contamination Studies
Urban groundwater is a large scale problem because it involves processes that
occur in urban areas, most commonly counties or smaller areas. Large scale groundwater
studies (conducted at the county scale or finer) provide a closer insight to groundwater
quality by utilizing site-specific data. These local scale groundwater studies provide
more meaningful results for groundwater managers because they include local conditions,
exceptions and field data analysis. The finer scale approach requires fewer assumptions
about the conditions applied in groundwater analysis methods, producing clearer results.
This approach also supports the use of tailored data collection and the inclusion of site-
specific factors that can contribute to groundwater contamination, providing a clearer
picture of the processes affecting groundwater pollution in specific areas.
Multiple methods have been used for groundwater investigations on the local
scale. One approach is the development of groundwater and constituent fate and
transport models (Kehew et al., 1996; Mitchell et al., 2001; Wilson et al., 1993). Almasri
and Kaluarachchi (2007), for example, developed a nitrate fate and transport model that
utilized land use data and examined the relationship between point and non-point sources
and nitrate levels in the soil. Their model, which was successfully verified with
groundwater monitoring data, utilized the spatial distribution of on-ground nitrogen
loadings, a simulation of soil nitrogen processes including mineralization, nitrification
10
and denitrification, and a model of the groundwater flow processes. Lee et al. (2006)
achieved similar success using a nutrient fate and transport model to describe the nitrogen
content in the groundwater. Both of these models provide groundwater managers with
important information about those processes that affect pollutants transport beyond the
water table.
Another approach to large scale groundwater studies has been through the
coupling of GIS software and statistical studies to examine the sources and spatial
distributions of groundwater pollution (Ahn and Chon, 1999; Kaçaroğlu and Günay,
1997; Pacheco and Caberera, 1997). Hudak and Sanmanee (2003) best demonstrate this
method of groundwater analysis in a selection of counties in central Texas. Their study
uses GIS and statistical analysis to examine the correlations between solutes (nitrate,
chloride, sulfate and fluoride), well depth and land use. The study concluded that there
was no statistically significant correlation between solute samples exceeding the
maximum contaminant level (MCL) for drinking water and land use. However, there
was a positive correlation determined between chloride and sulfate samples exceeding the
MCL limit, as well as an inverse correlation found between nitrate samples exceeding the
MCL limit and well depth, a conclusion also noted by several other studies (Ahn and
Chon, 1999; Eckhardt and Stackelburg, 1995; Gardner and Vogel, 2005; Hudak, 1999,
2000; Pacheco and Cabrera, 1997; Tesoriero and Voss, 1997). Groundwater managers
can utilize these studies to understand the spatial patterns of pollution in their region.
Another approach to local groundwater pollution studies is the use of weighted
overlay or regression methods to demonstrate the correlation between groundwater
11
pollution and its sources. In general there are two such approaches, regression models
withpredetermined variables and exact weights, such as DRASTIC and SINTACS (Fritch
et al., 2000; Ducci, 1999; Masetti et al., 2008; Napolitiano and Fabbri, 1996; Van
Stempvoort et al., 1993), or regression models that determine the degree of correlation
between possible variables and instances of groundwater pollution (Eckhardt and
Stackelberg, 1995; Gardner and Vogel, 2005; Kaown et al., 2007). These methods
produce maps which show the probability or susceptibility of each area to groundwater
pollution based on the weighted combination of the examined explanatory variables. The
DRASTIC and SINTACS models use the variables depth to water, net recharge, aquifer
media, soil media, topography, impact of vadose zone media and hydraulic conductivity,
while other regression models have examined variables such as land use and population
density. Groundwater susceptibility maps help groundwater managers identify
vulnerable areas in regions that should be monitored for pollution levels.
A final approach to local groundwater quality studies utilizes geostatistics
(Goovaerts et al., 2005, Lin et al., 2001, Liu et al., 2004; Pozdnyakova and Zhang, 1999).
Geostatistics produces a continuous surface using collected groundwater samples and
utilizing spatial relationships and statistics to determine the most likely values for the
resulting surface at unmeasured locations. One of the major benefits of geostatistics is
the lowered cost of field data collection while producing equally, if not more, accurate
results. For groundwater quality studies, interpolated surfaces can show the constituent
pollution across an area, and can be combined with other interpolated surfaces to create a
groundwater quality map (Nas and Berktay, 2010). However, since the most important
12
part of utilizing geostatics is the selection of the interpolation model, many studies have
focused on comparing and determining which model produces the most accurate results
for their data set (D’Agostino et al., 1998; Dash et al., 2010).
2.3 Groundwater Contamination in California
Numerous studies have examined groundwater quality in the state of California,
including some groundwater quality studies that have focused on the groundwater basins
in Los Angeles County. The five most notable studies and their findings have been
outlined in Table 1 and discussed below. In 2003, the California Department of Water
Resources completed the fifth update to the Bulletin 118 series, a set of groundwater
studies that began in 1952. This groundwater study investigated thousands of public
supply wells in the South Coast regional study area, which included basins from parts of
Los Angeles, Ventura, Orange, Riverside, San Bernardino and San Diego Counties. The
study determined 16% of wells exceeded maximum contaminant levels for nitrates and
5% exceeded maximum contamination levels for inorganics, such as total dissolved
solids (TDS) (California Department of Water Resources, 2003).
The U.S. Geological Survey (USGS) has also completed two notable studies on
groundwater quality in Los Angeles County. From 1995 to 2002, the USGS conducted a
spatial analysis of the groundwater quality in the four sub-basins of Los Angeles Coastal
Plain basin: Central, West Coast, Santa Monica and Hollywood (Figure 1). The study
collected hydraulic, geologic and chemical data from 20 new and 58 existing wells across
the basin. The instances of TDS and chloride contamination were found to be strongly
correlated (r
2
= 0.98) and were spatially concentrated along the coast of the study area
13
Table 1: Summary of notable Los Angeles County groundwater contamination studies.
Study Period Location Noted Contamination
California Department
of Water Resources,
Bulletin 118
2003 Basins from Los Angeles,
Ventura, Orange, Riverside,
San Bernardino and San
Diego Counties
Nitrates and TDS
contamination
U.S. Geological Survey 1995-
2002
Los Angeles Coastal Plain
basin
Chloride, sulfate and
TDS contamination
U.S. Geological Survey
GAMA Study
2005 San Fernando, San Gabriel
and Raymond basins
Nitrate and TDS
contamination
U.S. Geological Survey
GAMA Study
2006 Los Angeles Coastal Plain
basin
Boron, chloride,
sulfate, and TDS
contamination
U.S. Geological Survey
GAMA Study
2007 Santa Clara River Valley
basin
Chloride, sulfate and
TDS contamination

and deeper in the groundwater basin. Sulfate contamination was found along the south
coast of the study area but showed no trend of contamination with depth. There were no
instances of contamination by nitrates (Reichard et al., 2003).
The Groundwater Ambient Monitoring Assessment (GAMA) Program is the
second notable study completed by the U.S. Geological Survey. This study was
completed in cooperation with the State Water Resource Control Board and included
three separate studies of groundwater basins in Los Angeles County. Twenty-four wells
were monitored in the San Fernando, San Gabriel and Raymond groundwater basins from
May to July 2005. Multiple groundwater solutes and variables were examined, including
salt and nutrient constituents. The nutrient constituent measurements were compared
against the U.S. maximum contaminant levels (MCL-US) as well as the California
maximum contaminant levels (MCL-CA); often these limits are the same. The chloride,
14
sulfate and TDS salt constituents were also compared to the California Department of
Public Health secondary maximum contaminant levels (SMCL-CA), which have both an
upper and lower threshold for each constituent. The boron samples were compared
against the California Department of Public Health notification level limits (NL-CA).
Nitrate exceeded the MCL-US threshold in one well and TDS exceeded the SMCL-CA
lower threshold in six wells (Land and Belitz, 2008).
Twenty-six wells were monitored in the Santa Clara River Valley Basin from
April to June 2007 as a part of the GAMA study. These wells exceeded the SMCL-CA
lower thresholds for chloride, sulfate and TDS in one, nine and eight wells, respectively,
and the SMCL-CA upper thresholds in four, ten and 18 wells, respectively (Montrella
and Belitz, 2009). Nineteen wells in the four sub-basins of the Los Angeles Groundwater
Basin (Central, Hollywood, Santa Monica and West Coast) were monitored from June to
November 2006 in this study as well. Sulfate and TDS concentrations exceeded the
SMCL-CA lower threshold in one well each; the chloride, sulfate and TDS
concentrations exceeded the SMCL-CA upper threshold in one, one and 13 wells,
respectively, and the boron concentration exceeded the NL-CA level in one well
(Mathany et al., 2009). The monitoring periods were not long enough to examine
temporal trends and no attempts were made to analyze spatial patterns in these studies
either.
15
Chapter 3 - Data and Methods
3.1 Study Area
Los Angeles County provides an important study area for salt and nutrient
groundwater contamination due to the large urban population, the proximity to the ocean
and the semi-arid climate. The geologic conditions of the basin provide the most direct
contribution to the quality and availability of groundwater. The regional geology is
dominated by the large bend in the San Andreas Fault which formed an east-west
mountain range, the Transverse Ranges, splitting Los Angeles County in half. The basins
that have formed in and around the Transverse Ranges are filled with alluvium eroded
from the mountains. The periodic change in sea-level also provided a source of
intermittent marine sediment deposition across the southern portion of the county.
The resulting geology consist of deposits, varying in thickness, of marine and
alluvial sediments, comprised of sand, gravel, and conglomerate with intermittent silt and
clay beds, of Holocene, Pleistocene, and Pliocene age (Mathany et al., 2009). The
unconsolidated and semi-consolidated sedimentary composition of these basins provides
the perfect setting for groundwater aquifers, while the intermittent layers of clay form
impenetrable barriers, known as aquitards, creating confined aquifers. The Los Angeles
County basins each contain multiple layered aquifers that vary in thickness. While the
top unconfined aquifers are subject to the direct leaching of pollution from the surface,
over time the pollution is able to travel between layers through cracks and faults into the
confined aquifers below. The pollution of these lower aquifers poses a larger problem
16
because the water flows slower at these depths creating an accumulation of pollution that
can take a long time to revert.
There are other natural conditions of the study area which contribute to the quality
and availability of groundwater in Los Angeles County including climate and the
proximity to the coastline. The county’s semi-arid climate, with an average of 15.5
inches of precipitation each year (National Weather Service Forecast Office, 2012), is
broken into a dry season from May through October, and a wet season from November to
April during which almost all of the annual precipitation falls. This small amount of
precipitation provides moderate recharge to the groundwater basins during the winter and
nearly no recharge during the summer. Los Angeles County also has 75 miles of
coastline, creating the threat of salt-water intrusion to the basins closest to the coast.
While this issue has been addressed through the use of injection wells that pump water
into the groundwater table, pushing the intruding seawater plume back toward the
coastline (Johnson, 2007; Mathany et al., 2009), it remains an active concern for Los
Angeles County’s groundwater managers.
With a population of 9.8 million people in Los Angeles County there are multiple
sources of urban groundwater pollution that can negatively affect the underlying
groundwater basins. Urbanization impacts the quantity of available groundwater through
the large proportion of impenetrable surfaces, such as paved roads, parking lots and
buildings, which limit the ability for precipitation to seep through the soil and recharge
the groundwater (Barrett, 2008). The land use of the county includes urban residential,
commercial, and industrial, each of which produces its own salt and nutrient
17
contaminants that can infiltrate and pollute a groundwater basin. Urban storm water
runoff is a form of non-point source pollution including, street litter, animal wastes,
combined sewer overflows, and construction and industrial activity wastes, among others
(Nussbaum, 1990). This run-off may carry the pollution into the groundwater where
infiltration and percolation occur. Other sources of urban water pollution include
underground storage tanks, landfills, leaking sewers and industrial and retail locations
that spill chemical solvents (Lerner, 2008).
This thesis study investigates four salt contaminants that commonly appear as
urban groundwater pollutants: boron (B), chloride (CL), sulfate (SO
4
) and total dissolved
solids (TDS). Boron is often used as an additive in detergent, fertilizer, glass, ceramics
and cosmetics (Zhao and Liu, 2010), all of which are common contributors to pollution in
urban sewage, landfills and storm water runoff. Household sewage, landfill leachate,
industrial effluent, urban runoff and saline intrusion have all been noted as sources of
chloride (Nas and Berktay, 2010; Hudak and Sanmanee, 2003). Sulfates are used
commercially in the chemical industry and are discharged into groundwater through
industrial wastes (Nas and Berktay, 2010) as well as through sewage and landfill
leachates (Hudak and Sanmanee, 2003). The constituent total dissolved solids (TDS)
measures the minerals, metals and other compounds in solution (Nussbaum, 1990).
Elevated total dissolved solids concentrations have been attributed to fertilizers, oil field
brines, industrial discharges and sewage effluents (Matsumoto, 2010).
Four nitrogen contaminants common in urban groundwater pollution were also
investigated in this thesis study: nitrite-nitrogen (NO
2
-N), nitrate (NO
3
), nitrate-nitrogen
18
(NO
3
-N) and nitrite-nitrogen plus nitrate-nitrogen (NO
2
-N+NO
3
-N). Leachate from
septic systems, urban runoff, and combined sewage overflow are important urban sources
of nitrogen (Puckett, 1994). Urbanization also provides a large source of nitrogen
pollution that can infiltrate groundwater through the combustion of fossil fuels (Puckett,
1994; Hudak and Sanmanee, 2003). The dense population of motor vehicles in Los
Angeles County has contributed to the degradation of the air quality, providing
conditions that are commonly referred to as ‘smog.’ The chemicals released into the air
through the burning of fossil fuels are redistributed to the ground through atmospheric
deposition, another large source of nitrogen pollution to the area.
There are 10 groundwater basins within Los Angeles County (Figure 1). These
basins vary greatly in their size as well as the current state of groundwater quality and
availability. The smallest basins include Malibu Valley (613 acres), Russell Valley
(3,100 acres), Raymond (26,200 acres), and Santa Clara River Valley East (66,200 acres).
The Malibu Valley groundwater basin, located along the west coast of Los Angeles
County, drains toward the coastline to the south. Both the Russell and Santa Clara River
East groundwater basins, located in the northwest corner of Los Angeles County, flow
into larger groundwater basins located in Ventura County to the north. The Raymond
groundwater basin, located between the San Fernando and San Gabriel basins, flows
directly into the San Gabriel basin, located to the southeast. The San Fernando (145,000
acres), San Gabriel (154,000 acres) and the Los Angeles Coastal Plain (310,900 acres)
are the largest groundwater basins in Los Angeles County. The San Fernando and San
Gabriel basins are located within the Transverse Ranges; these groundwater basins flow
19
south, through the small drainage pathways that wander through the mountains and into
the Central sub-basin of the Los Angeles Coastal Plain basin. The Los Angeles Coastal
Plain basin is broken into four sub-basins: the Santa Monica basin (32,100 acres) to the
northwest, the Hollywood basin (10,500 acres) to the north, the West Coast basin (91,300
acres) to the west and the Central basin (177,000 acres) to the east. The groundwater
flow patterns in this area are affected by sea-water intrusion injection along the coastline
in the west and southwest portions of the basin, which directs the groundwater flow away
from the coast. The groundwater flows in a southeast direction in the remainder of the
basin.

Figure 1: Los Angeles County’s groundwater basins.
There are documented salt and nutrient groundwater quality issues in several of
the Los Angeles County groundwater basins. Both the San Fernando and San Gabriel
20
Basins have historically contained high concentrations of nitrate from subsurface sewage
disposal and past agricultural activities (California Regional Water Quality Control
Board, 1994). With discontinuous confining layers in these alluvial basins, the pollutants
have been able to seep through to the groundwater. In the San Gabriel Basin,
approximately 20% of the groundwater production for municipal use has been closed due
to pollution (California Regional Water Quality Control Board, 1994). The four sub-
basins of the Los Angeles Coastal Plain groundwater basin have documented salt and
nutrient groundwater quality issues including seawater intrusion near the coastline and
organic as well as inorganic pollutants originating from leaking tanks, leaking sewer lines
and illegal discharges (California Regional Water Quality Control Board, 1994). The
issue of seawater intrusion has been addressed through injection wells which have formed
a freshwater barrier along the coastline; however, their effectiveness must be
continuously monitored. In addition, the discontinuous confining layers in these alluvial
basins have also provided a path for pollutants to slowly filtrate to deeper aquifers
(California Regional Water Quality Control Board, 1994).
The State Water Resource Control Board (State Board) is the California agency in
charge of designating the beneficial uses of the surface and groundwater as well as the
narrative and numerical objective that must be attained and maintained for acceptable
groundwater quality. In Los Angeles County, the Los Angeles Regional Water Quality
Control Board (Regional Board) is the local agency in charge of these designations. The
Basin Plan began setting numerical limits for Los Angeles and Ventura County
groundwater quality in 1952. Since then there have been multiple revisions to address
21
the changes in groundwater quality and management, the most recent being completed in
1994. The 1994 Basin Plan revision designates the numerical limits that each of the eight
constituents in this thesis study must meet to maintain an acceptable level of groundwater
quality. The limits attributed to the four salt constituents vary by basin and are
summarized in Table 2. In addition, salt constituent limits vary across each basin, but
since this thesis is conducting analysis at the basin scale, the lowest limits designated for
each constituent were applied to the whole basin. The nutrient limits are uniform across
all county basins: ground waters shall not exceed 1 mg/L as nitrite-nitrogen (NO
2
-N), 45
mg/L as nitrate (NO
3
), 10 mg/L as nitrate-nitrogen (NO
3
-N) and 10 mg/L nitrogen as
nitrate-nitrogen plus nitrite-nitrogen (NO
2
-N + NO
3
-N) (California Regional Water
Control Board, 1994). Nitrate and nitrate-nitrogen are both varieties of the nitrate
nutrient which occur in nature in two different forms. The nitrate nutrient is 4.4 times
heavier in molecular weight than the nitrate-nitrogen nutrient; therefore, the nitrate limit
is approximately 4.4 times larger than the nitrate-nitrogen limit (45 and 10 mg/L,
respectively).
These eight salt and nutrient constituents, also generally referred to as analytes,
commonly exceed their designated standards, which has led the Regional Board to begin
the development of individual salt and nutrient management plans for each of the
groundwater basins in the county. The goal of salt and nutrient management planning is
to understand the present level of pollution, calculate the assimilative capacity of each
salt and nutrient and develop a remediation strategy to obtain lower levels of salt and
nutrient pollution in each basin. This thesis study will support the salt and nutrient plan
22
Table 2: Groundwater constituent limits (in mg/L) by groundwater basin (California Regional Water
Control Board, 1994).
Basin Sub Basin Boron Chloride Sulfate TDS
Los Angeles Coastal Plain Central 1.0 150 250 700
Los Angeles Coastal Plain Hollywood 1.0 100 100 750
Los Angeles Coastal Plain Santa Monica 0.5 200 250 1,000
Los Angeles Coastal Plain West Coast 1.5 250 250 800
San Fernando 1.5 100 300 700
San Gabriel 0.5 100 100 450
Raymond 0.5 100 100 450
Russell Valley 1.0 250 500 1,500
Malibu Valley 2.0 500 500 2,000
Santa Clara River Valley Santa Clara River
Valley East
0.5 100 150 700

process by characterizing the spatiotemporal patterns of four salt constituents and four
nutrient constituents and their instances of exceeding the limit in each of Los Angeles
County’s 10 groundwater basins.
3.2 Groundwater Data Collection and Management
Groundwater data was downloaded from the State Water Resources Control
Board Geotracker website (http://geotracker.waterboards.ca.gov/). Geotracker is the
State Water Resource Board’s data management system that contains information on all
sites which are both managed by the State Water Resource Board and impact
groundwater, including active and closed underground storage tanks, site clean-up
programs, and land disposal sites. This system allows for sites to upload electronic
groundwater data as required by their regulatory permits. The system compiles these
data and provides an interactive GIS interface to view the sites and makes the data
available for download by county.
The data used in this study was downloaded in September 2011 from the
‘Download ESI Data” page of the Geotracker data management site. Three files were
23
obtained: (1) the EDF dataset - Electronic Deliverable Format data which contains every
constituent measurement at every site that has been submitted electronically to the
Regional Board, and similarly, (2) the Geo_XY dataset - a table of all of the sites in Los
Angeles County and their geographic coordinates, and (3) the Geo_Well dataset - a table
of all of the depth to groundwater measurements taken at each site. The data dictionaries
for these three tables were also obtained from the Geotracker data management site and
used for reference.
GIS data describing the boundaries of the 10 groundwater basins in Los Angeles
County were also obtained. Specifically, a polygon shapefile was downloaded from the
Department of Water Resources Bulletin 118 groundwater basin maps and descriptions
website
(http://www.water.ca.gov/groundwater/bulletin118/gwbasin_maps_descriptions.cfm).
The file contained the polygon areas of all the groundwater basins in California, of which
the 10 groundwater basins in Los Angeles County were selected and clipped for use in
this thesis study. In addition, the GIS data for the boundary of Los Angeles County was
acquired from the Los Angeles County GIS Data Portal website
(http://egis3.lacounty.gov/dataportal/).
The EDF data file was imported into SAS Business Analytics Software in order
to extract the data for the eight targeted constituents of this study: boron (B), chloride
(CL), sulfate (SO
4
), total dissolved solids (TDS), nitrite nitrogen (NO
2
-N), nitrate (NO
3
),
nitrate-nitrogen (NO
3
-N) and nitrate-nitrogen plus nitrite-nitrogen (NO
3
-N+NO
2
-N). The
exported data was cleaned up by removing measurements made in units that were unable
24
to translate to mg/L because they required a density calculation in order to be converted
(i.e. mg/kg, PPM and percent), resulting in the removal of 0.09% of the data. All
measurements in µg/L units were converted into mg/L. The remaining data were then
joined to the Geo_XY data table to provide geographic locations for the constituent
measurements to be analyzed spatially. The Geo_XY locations were only matched to
75% of the EDF data, and further, only 66% of the data points fell within the boundaries
of the 10 groundwater basins in Los Angeles County.
Each of the returned data points was next assigned to a season based on the day
that the constituent measurement was taken: summer, coded as S.YY, (May through
October) and winter, coded as W.YY-YY, (November through April) according to the
annual precipitation patterns in Los Angeles County. The EDF data ranged from July
2001 through June 2011; because summer 2001 and summer 2011 did not contain data
for every month in the season, these data points were removed from the set. Taken as a
whole, 64% of the original data set was retained and used for the evaluation conducted in
this thesis study.
The removal of some of the original data might have altered the spatiotemporal
patterns that characterize Los Angeles County in this thesis study. Table 3 was used to
investigate how this data cleaning process might have affected the characteristics of the
data. The comparison shows that the average concentrations decreased for all of the salt
constituents (boron, chloride, sulfate, and TDS), whereas the concentrations increased for
three of the four nutrient constituent averages (nitrate, nitrate-nitrogen, and nitrite-
nitrogen plus nitrate-nitrogen) following data removal. The nitrite-nitrogen constituent
25
showed the least change. Overall, these changes suggest that the salt constituent data
used in this study will most likely contain a smaller fraction of samples exceeding the
standard than the larger, all-inclusive dataset, while the nutrient constituent data used in
the study will more than likely contain a larger fraction of samples exceeding the
standard than the larger, all-inclusive dataset. This effect on the data set was taken into
account when analyzing the results of the analysis.
Table 3: Changes in constituent statistics following data removal as directed in the text.
Dataset
#
Samples
Average Std. Dev. Minimum Maximum
Original
5,185 0.84 1.71 0 34
B
Final
2,707 0.59 1.24 0 23
Original
16,474 289.81 1,118.74 0 24,100
CL
Final
8,629 226.68 849.68 0 20,000
Original
54,892 528.11 1,746.89 0 93,000
SO4
Final
37,285 512.04 2,024.48 0 93,000
Original
12,885 2,342.52 6,510.53 0 315,000
TDS
Final
6,817 2,117.17 5,694.50 0 97,500
Original
5,713 0.12 1.62 0 88
NO2N
Final
3,336 0.10 1.63 0 88
Original
8,608 10.07 24.04 0 560
NO3
Final
4,839 10.93 25.05 0 460
Original
40,167 4.32 11.30 0 800
NO3N
Final
28,407 4.48 10.90 0 800
Original
1,341 12.35 75.40 0 978
NO3-
NO2N
Final
734 20.99 101.00 0 978

The final EDF data set was then joined to the Geo_Well table using SAS to match
the well depth measurements taken on the closest day to the date each sample was taken
in the final EDF data set. Well depths were matched to 96% of the final EDF data. In
addition, the distance to the coastline was calculated with the Near analysis tool in the
ArcGIS Analysis Toolbox and added as a field to the final EDF table. These last data
26
management steps completed the final dataset utilized for the spatiotemporal analysis of
groundwater quality characteristics in Los Angeles County. The GIS analysis was
conducted using Esri’s ArcGIS 10.0 mapping software. The data set was documented in
the metadata as having been collected in the North American Datum of 1983 (NAD 83)
and was mapped in ArcMap 10.0 in the Geographic Coordinate System (GCS) North
American 1983.
3.3 Methods of Analysis
Data exploration, the first step of the analysis, began with an evaluation of the
spatial characteristics of the Geotracker dataset. Since these samples were all collected
from monitoring wells at permitted sites, the samples are found in clusters across the
groundwater basins. Figure 2 displays the clusters as they can be observed at the basin
and sub-basin scales. The limited spatial distribution of this data reveals the limited
options for methods of spatial analysis because the location, depth and time interval
variables of the sampling events are not controlled, an assumption that many spatial
analysis techniques make.
With the limiting spatial analysis options, a tabular analysis was conducted first
on each of the salt and nutrient constituents in each of the groundwater basins to
determine the presence of increasing or decreasing trends in the percentage of samples
exceeding the respective Basin Plan limits (see Tables 4 through 10). Once the tables
were analyzed, certain constituents required graphs to further aid in the visualization and
recognition of trends in the percent of samples exceeding the respective Basin Plan limits
(see Figures 3, 5, 7 and 9). Additional analysis was conducted to examine spatiotemporal
27

Figure 2: Maps showing clusters of samples that dominate the Geotracker dataset.
trends of select constituents in select basins to aid in the determination of the impact of
the changes in samples sizes and locations of sampling sites on the identified trends in the
percentages of samples exceeding the respective Basin Plan limits (see Figures 4, 6, and
8).
Groundwater basins comprised of alluvial material, like the 10 basins in Los
Angeles County, have multiple deposits of alluvium forming both permeable (aquifers)
and impermeable layers (aquitards). The groundwater quality can be substantially
different in each layer of these alluvial basins based on the amount of pollution that
permeates to each depth and the vertical rate of flow of the groundwater. In order to
better understand from what depth the groundwater quality data is originating from, the
depth to water was analyzed in comparison to the percentage of samples exceeding the
respective Basin Plan limits for each constituent in the 10 Los Angeles County basins.
The depth to groundwater was divided into equal sample quintiles with the following
28
class limits: -0.91 to 14 feet, 14.01 to 24.47 feet, 24.48 to 35.57 feet, 35.58 to 60.56 feet,
60.57 to 780.47 feet, and samples with no corresponding depth to groundwater
measurements, ‘no data.’ The salt or nutrient constituent’s total and percentage of
samples exceeding the standard was analyzed for each of the groundwater depth classes
(see Table 11; Figures 10 and 11).
Due to the documented groundwater quality issues of salt water intrusion in the
four basins of the Los Angeles Coastal Plain groundwater basin (Central, Hollywood,
Santa Monica and West Coast), the distance to the coastline was analyzed together with
the percentage of samples exceeding the Basin Plan limit to better characterize the links,
if any, between salt water intrusion and groundwater quality degradation. The distance to
coastline was broken down into five equal distance intervals: nearest (0 to 3.74 miles),
near (3.75 to 7.48 miles), mid (7.49 to 11.23 miles), far (11.24 to 14.97 miles) and
furthest (14.98 to 18.71 miles). The relationship between the fraction of samples
exceeding the respective Basin Plan limits and the distance to the coastline intervals was
analyzed for each salt constituent (see Table 12).
29
Chapter 4 - Results and Discussion
4.1 Groundwater Spatiotemporal Analysis
4.1.1 Salt Constituents
Boron was sampled 2,707 times in Los Angeles County from November of 2001
to April 2011 and 11% of these samples exceeded the respective Basin Plan limits. The
Central, West Coast, San Fernando, San Gabriel and Santa Clara basins contained the
majority of boron sampling events (Table 4). Consistent sampling in each of these basins
was established during different seasons (San Fernando, summer 2004; West Coast, San
Gabriel and Santa Clara, winter 2004-2005; and Central, winter 2005-2006) and has
continued since without interruption. The Central and Santa Clara basins contained
higher levels of boron, with 21% and 24% of the samples exceeding the corresponding
Basin Plan limits, respectively. A winter and summer seasonal trend was not found in
any of the basins. The San Fernando and San Gabriel basins displayed consistently low
percentages of boron samples exceeding the respective Basin Plan limits. The Central,
West Coast, and Santa Clara basins all displayed increasing percentages of samples
exceeding the respective Basin Plan limits. However, each of these basins increased at
different rates: the Santa Clara basin rapidly increased in summer 2006, the Central basin
increased gradually between summer 2006 and summer 2008, and the West Coast basin
steadily increased from summer 2008 to present day. In addition, each of these three
basins contained widely varying sampling sizes in each season; this may have contributed
to the trend of increasing percentages of samples exceeding the respective Basin Plan
limits in these instances.
30
Table 4: The number and fractions of boron samples exceeding the respective Basin Plan limits, in each
basin, during each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San
Gabriel
Raymond
Russell
Malibu
Santa
Clara
L.A.
County
% Exceed 0% 0% - - - - - - - - 0%
W.01-02
# Samples 1 4 - - - - - - - - 5
% Exceed - - - - - - - - - - -
S.02
# Samples - - - - - - - - - - -
% Exceed - - - - - - - - - - -
W.02-03
# Samples - - - - - - - - - - -
% Exceed - 0% - - - - - - 0% - 0%
S.03
# Samples - 16 - - - - - - 5 - 21
% Exceed 0% 0% - - - - - - 0% - 0%
W.03-04
# Samples 3 19 - - - - - - 6 - 28
% Exceed - 0% 0% - 7% - - - 0% - 3%
S.04
# Samples - 7 9 - 15 - - - 3 - 34
% Exceed - 0% 0% 0% 4% 0% - - 0% 13% 4%
W.04-05
# Samples - 17 21 20 27 3 - - 3 30 121
% Exceed - - 0% 0% 25% 0% - - - 17% 11%
S.05
# Samples - - 7 20 16 10 - - - 36 89
% Exceed 0% - - 0% 0% 0% - - - 17% 6%
W.05-06
# Samples 1 - - 25 25 9 - - - 36 96
% Exceed 5% - 0% 9% 0% 0% - - - 25% 9%
S.06
# Samples 56 - 7 23 46 13 - - - 57 202
% Exceed 3% 100% 0% 0% 0% 0% - - - 31% 10%
W.06-07
# Samples 33 6 5 72 30 14 - - - 42 202
% Exceed 14% - 0% 0% 0% 0% - - - 31% 10%
S.07
# Samples 22 - 6 33 44 15 - - - 42 162
% Exceed 9% - 0% 0% 0% 0% - - - 31% 9%
W.07-08
# Samples 35 - 6 32 44 15 - - - 42 174
% Exceed 30% 0% 0% 0% 16% 0% - - - 29% 13%
S.08
# Samples 61 50 15 49 44 25 - - - 38 282
% Exceed 27% 0% - 6% 6% 0% - - - 25% 13%
W.08-09
# Samples 74 33 - 33 64 36 - - - 36 276
% Exceed 27% 0% 0% 10% 0% 0% - - - 21% 15%
S.09
# Samples 75 2 2 52 29 26 - - - 38 224
% Exceed 21% - 17% 5% 0% 0% - - - 25% 12%
W.09-10
# Samples 67 - 35 105 30 17 - - - 36 290
% Exceed 21% - 27% 10% 2% 0% - - - 17% 12%
S.10
# Samples 72 - 15 72 56 27 - - - 30 272
% Exceed 38% - 0% 31% 1% 0% - - - 30% 21%
W.10-11
# Samples 58 - 2 36 76 13 - - - 44 229
% Exceed 21% 4% 8% 6% 3% 0% - - 0% 24% 11%
Totals
# Samples 558 154 130 572 546 223 - - 17 507 2707

31
Chloride was sampled 8,629 times in Los Angeles County from November 2001
through April 2011; 35% of these measurements exceeded the respective Basin Plan
limits. During this time, the Raymond, Russell, and Malibu basins had few or no
chloride samples collected, therefore these basins were not analyzed with the other seven
basins (Table 5). A trend between the winter and summer seasons was not observed in
any of the basins. The Central, Santa Monica and Santa Clara basins maintained
consistent percentages of samples exceeding the respective Basin Plan limits throughout
the analysis period. The fraction of samples exceeding the Basin Plan limit in the San
Fernando basin decreased over the time period (Figure 3), but this trend was coupled with
an increase in the number of samples collected per season. This change in sample
support might have contributed to the decrease in the percentage of samples exceeding

Figure 3: The percentage of chloride samples exceeding the respective Basin Plan limits, during each
season, in the seven analyzed basins.

32

Table 5: The number and fractions of chloride samples exceeding the respective Basin Plan limits, in each
basin, during each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San
Gabriel
Raymond
Russell
Malibu
Santa
Clara
L.A.
County
% Exceed 64% 0% 12% - 92% - - - - - 24%
W.01-02
# Samples 14 19 82 - 12 - - - - - 127
% Exceed 0% 0% 0% 100% 92% - - - - - 13%
S.02
# Samples 1 15 72 2 12 - - - - - 102
% Exceed 38% 0% 0% 91% 83% - - - - - 41%
W.02-03
# Samples 26 17 1 11 6 - - - - - 61
% Exceed 25% 0% 0% 0% - - - - 0% - 4%
S.03
# Samples 12 30 19 1 - - - - 5 - 67
% Exceed 43% 0% - 67% - - - - 0% - 28%
W.03-04
# Samples 23 36 - 21 - - - - 6 - 86
% Exceed 25% 17% 0% 86% 13% - - - 0% - 33%
S.04
# Samples 12 24 9 22 15 - - - 3 - 85
% Exceed 39% 15% 0% 62% 70% 0% - - 0% 31% 38%
W.04-05
# Samples 148 41 37 78 27 5 - - 3 35 374
% Exceed 49% 67% 8% 54% 76% 55% - - - 33% 51%
S.05
# Samples 67 73 40 150 29 33 - - - 36 428
% Exceed 42% 25% 17% 58% 27% 47% - - - 31% 42%
W.05-06
# Samples 158 52 104 276 78 36 - - - 36 740
% Exceed 42% 27% 5% 28% 16% 52% - - - 24% 28%
S.06
# Samples 203 52 61 172 176 33 - - - 38 735
% Exceed 24% 37% 6% 61% 17% 50% - - - 29% 31%
W.06-07
# Samples 137 49 77 123 109 34 - - - 38 567
% Exceed 36% 44% 13% 22% 20% 58% - - - 29% 28%
S.07
# Samples 176 36 68 88 173 38 - - - 38 617
% Exceed 37% 42% 0% 39% 25% 64% - - - 32% 34%
W.07-08
# Samples 287 38 38 74 139 33 - - - 38 647
% Exceed 50% 36% 5% 44% 20% 59% - - - 28% 39%
S.08
# Samples 313 120 39 106 155 37 - - - 36 806
% Exceed 35% 32% 14% 33% 26% 78% - - - 31% 34%
W.08-09
# Samples 278 98 28 93 184 54 - - - 36 771
% Exceed 39% 17% 13% 29% 25% 77% - - - 32% 34%
S.09
# Samples 285 54 31 83 147 44 - - - 38 682
% Exceed 43% 83% 12% 42% 21% 72% - - - 33% 38%
W.09-10
# Samples 312 18 68 107 119 36 - - - 36 696
% Exceed 38% 89% 13% 55% 21% 56% - - - 43% 39%
S.10
# Samples 211 27 15 97 148 27 - - - 30 555
% Exceed 37% 63% 0% 56% 10% 56% - - - 34% 32%
W.10-11
# Samples 107 19 2 98 186 27 - - - 44 483
% Exceed 40% 33% 9% 48% 23% 61% - - 0% 31% 35%
Totals
# Samples 2770 818 791 1602 1715 437 - - 17 479 8629

33
the Basin Plan limit, but this result does suggest that a decrease in chloride concentrations
has occurred in the San Fernando basin since 2001. There is also a sudden decrease in
the percentage of samples exceeding the respective Basin Plan limits during the winter
2010-2011 season in six of the seven basins (excluding the West Coast basin), which
could have been caused by a regional scale factor, such as a lower than average
precipitation during this winter season.
The San Gabriel and West Coast basins contain the highest levels of chloride
readings across the 10-year period, 61% and 48% of samples exceeded the corresponding
Basin Plan limits, respectively. The percentages of samples exceeding the respective
Basin Plan limits in the San Gabriel and Hollywood basins increased with time (Figure 3)
given relatively consistent numbers of samples in each season. While there were several
spatiotemporal analyses that would illustrate the chloride trends in Los Angeles County
groundwater basins, a spatiotemporal analysis was completed on the Hollywood basin in
order to further investigate if the reason for the increase in samples exceeding the Basin
Plan limit could be ascribed to changes in sampling locations or rather a real increase in
chloride concentration (Figure 4). The spatiotemporal analysis showed that the samples
collected in the Hollywood basin since 2001 were clustered around 10 sites, where
multiple samples were collected at a finer scale. Due to the lack of scattered samples,
spatial trends are difficult to determine. However, a relationship is seen in seasons where
a high percentage of the samples exceeding the Basin Plan limit were collected almost
exclusively from the southwest corner of the basin (summer 2005, winter 2009-2010,
34

Figure 4: Spatial distribution of chloride samples in the Hollywood basin, during each season.
summer 2012 and winter 2010-2011), whereas seasons in which samples were collected
from multiple locations displayed a lower percentage of samples exceeding the Basin
Plan limit (winter 2005-2006 through summer 2009). This relationship indicates that the
groundwater in the southwest corner of the basin contains higher levels of chloride than
the other sites across the basin.
35
A total of 37,285 sulfate samples have been collected in Los Angeles County
since November 2001; 37% of these samples exceeded the respective Basin Plan limits.
Both the Raymond and Malibu Valley basins did not have continuous sulfate sampling
over the 10-year period, and were excluded from further analysis (Table 6). None of the
eight analyzed basins displayed a trend between the summer and winter seasons. The
eight analyzed basins can be divided into two groups based on the ranges of the
percentage of samples exceeding the respective Basin Plan limits. The Central, Santa
Monica, West Coast and San Fernando basins have the lower range of percentages, all
below 50%, while the Hollywood, San Gabriel, Russell and Santa Clara basins have a
higher range of percentages, all above 55% (Figure 5). All of the basins have displayed
consistent percentages over the 10-year time period, except for the Russell basin, which

Figure 5: The percentage of sulfate samples exceeding the respective Basin Plan limits, during each
season, in the eight analyzed basins.

36
Table 6: The number and fractions of sulfate samples exceeding the respective Basin Plan limits, in each
basin, during each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San Gabriel
Raymond
Russell
Malibu
Santa Clara
L.A.
County
% Exceed 33% 70% 35% 37% 36% 67% - - - - 37%
W.01-02
# Samples 648 30 147 364 257 70 - - - - 1516
% Exceed 35% 66% 47% 29% 46% 62% - - - - 39%
S.02
# Samples 786 44 163 335 286 69 - - - - 1683
% Exceed 34% 67% 12% 34% 40% 57% - - - - 36%
W.02-03
# Samples 801 58 81 374 180 58 - - - - 1552
% Exceed 36% 67% 41% 24% 56% 84% - - 20% 100% 41%
S.03
# Samples 594 69 99 325 260 44 - - 5 3 1399
% Exceed 32% 55% 25% 28% 45% 60% - 75% 0% 100% 35%
W.03-04
# Samples 681 76 55 331 238 62 - 16 6 3 1468
% Exceed 29% 63% 27% 36% 41% 55% - 100% 0% 33% 35%
S.04
# Samples 682 63 131 308 222 51 - 18 3 6 1484
% Exceed 33% 57% 30% 23% 27% 55% - 70% 0% 66% 33%
W.04-05
# Samples 833 91 172 424 265 91 - 37 3 35 1951
% Exceed 34% 70% 39% 32% 28% 62% - 96% 80% 64% 38%
S.05
# Samples 818 121 223 517 354 119 - 25 5 36 2218
% Exceed 35% 59% 28% 46% 34% 53% - 85% 86% 67% 40%
W.05-06
# Samples 947 93 246 649 376 136 - 34 7 36 2524
% Exceed 40% 59% 29% 40% 27% 65% - 85% 100% 53% 39%
S.06
# Samples 869 122 302 682 528 136 - 34 7 38 2718
% Exceed 33% 59% 19% 29% 33% 55% - 93% 100% 63% 35%
W.06-07
# Samples 936 87 230 536 487 138 - 61 5 38 2518
% Exceed 33% 73% 21% 33% 27% 65% - 88% 83% 68% 36%
S.07
# Samples 780 80 209 542 508 148 - 40 12 38 2357
% Exceed 35% 70% 23% 35% 32% 63% - 89% 100% 68% 38%
W.07-08
# Samples 923 76 183 531 485 152 - 44 8 38 2440
% Exceed 36% 70% 32% 35% 32% 70% 89% 59% 57% 67% 40%
S.08
# Samples 939 141 149 451 546 124 9 74 7 36 2476
% Exceed 34% 66% 32% 32% 31% 74% - 62% 88% 67% 39%
W.08-09
# Samples 1005 173 155 503 603 167 - 74 8 36 2724
% Exceed 37% 61% 34% 27% 23% 85% 100% 97% - 68% 40%
S.09
# Samples 570 72 86 315 265 110 8 36 - 38 1500
% Exceed 36% 61% 36% 26% 29% 76% 100% 67% - 67% 37%
W.09-10
# Samples 719 96 139 421 325 66 8 39 - 36 1849
% Exceed 35% 65% 34% 25% 39% 62% - 100% - 67% 38%
S.10
# Samples 565 60 80 310 302 74 - 22 - 30 1443
% Exceed 30% 56% 29% 22% 30% 84% 86% 87% - 70% 34%
W.10-11
# Samples 531 45 42 308 407 50 7 31 - 44 1465
% Exceed 34% 64% 30% 32% 33% 65% 94% 80% 68% 66% 37%
Totals
# Samples 14627 1597 2892 8226 6894 1865 32 585 76 491 37285

37
had highly variable readings, and the San Gabriel basin, which exhibited a modest
increase in the percentage of samples exceeding the Basin Plan limit over time. The
sampling size per season also varied in the San Gabriel basin, providing a possible
explanation for the increase in percentage of samples exceeding the respective Basin Plan
limit in addition to the conclusion that sulfate concentrations were in fact increasing in
the basin. To investigate further a spatiotemporal analysis was conducted (Figure 6) for
the sulfate trends in the San Gabriel basin, which showed that the samples collected are
concentrated along the southern portion of the basin, with the exception of a small cluster
of sample sites in the center of the basin. Unfortunately, the limited spatial distribution
of sites indicates that the results that are shown for San Gabriel basin may not be
indicative of the basin as a whole. However, since the samples were concentrated in the
southwest, the increase in the percentage of sites exceeding the respective Basin Plan
limit shows that the sulfate concentration in the southern portion of San Gabriel basin has
increased over time. Additionally, the sole sampling site in the center of the basin does
not contain samples exceeding the respective Basin Plan limit until the final two seasons
(summer 2010 and winter 2010-2011), suggesting that the sulfate levels may be
increasing in other portions of the basin as well.
A total of 6,817 total dissolved solids (TDS) samples have been collected in Los
Angeles County since November 2001. The TDS samples exhibited the highest
percentage of samples exceeding the respective Basin Plan limits (78%) of the eight
constituents analyzed in this thesis study. Due to a lack of TDS sampling in the
Raymond, Russell and Malibu basins, these basins were excluded from further analysis
38

Figure 6: Spatial distribution of sulfate samples in the San Gabriel basin, during each season.
(Table 7). In four of the remaining seven basins, continuous TDS sampling began at
varying times (Santa Monica and San Fernando basins, summer 2004; San Gabriel and
Santa Clara basins, winter 2004-2005). A winter and summer trend was not recognized
in any of the analyzed basins. The Central, West Coast, San Fernando and San Gabriel
basins displayed the highest percentages of samples exceeding the respective Basin Plan
39

Table 7: The number and fractions of TDS samples exceeding the respective Basin Plan limits, in each
basin, during each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San
Gabriel
Raymond
Russell
Malibu
Santa
Clara
L.A.
County
% Exceed 100% 58% 58% 90% 100% - - - - - 69%
W.01-02
# Samples 3 19 40 10 13 - - - - - 85
% Exceed 100% 53% - 100% 100% - - - - - 77%
S.02
# Samples 1 15 - 2 12 - - - - - 30
% Exceed 91% 53% 0% 100% 100% - - - - - 81%
W.02-03
# Samples 22 17 1 11 6 - - - - - 57
% Exceed 100% 83% - 100% - - - - 0% - 80%
S.03
# Samples 12 30 - 2 - - - - 5 - 49
% Exceed 100% 64% - 76% - - - - 0% - 70%
W.03-04
# Samples 16 36 - 21 - - - - 6 - 79
% Exceed 100% 71% 0% 100% 95% - - - 0% - 83%
S.04
# Samples 39 24 9 22 21 - - - 3 - 118
% Exceed 81% 68% 0% 74% 88% 60% - - 0% 57% 68%
W.04-05
# Samples 119 41 21 23 24 10 - - 3 35 276
% Exceed 88% 85% 29% 79% 82% 85% - - - 58% 77%
S.05
# Samples 34 73 24 108 51 33 - - - 36 359
% Exceed 87% 64% 59% 88% 95% 80% - - - 58% 80%
W.05-06
# Samples 166 44 103 222 38 35 - - - 36 644
% Exceed 94% 57% 43% 94% 97% 85% - - - 58% 84%
S.06
# Samples 194 44 60 216 63 33 - - - 38 648
% Exceed 86% 59% 35% 80% 83% 85% - - - 53% 72%
W.06-07
# Samples 191 49 86 110 53 34 - - - 38 561
% Exceed 95% 75% 46% 86% 98% 87% - - - 63% 81%
S.07
# Samples 129 36 90 132 86 38 - - - 38 549
% Exceed 90% 79% 40% 87% 89% 85% - - - 61% 79%
W.07-08
# Samples 143 38 57 89 64 33 - - - 38 462
% Exceed 88% 60% 21% 89% 91% 86% - - - 64% 75%
S.08
# Samples 185 102 63 87 77 37 - - - 36 587
% Exceed 82% 58% 38% 87% 71% 94% - - - 61% 74%
W.08-09
# Samples 168 86 40 84 145 54 - - - 36 613
% Exceed 88% 44% 21% 89% 79% 95% - - - 68% 77%
S.09
# Samples 142 52 24 64 39 44 - - - 38 403
% Exceed 88% 89% 24% 77% 81% 94% - - - 58% 77%
W.09-10
# Samples 171 18 42 83 101 36 - - - 36 487
% Exceed 86% 89% 29% 90% 76% 93% - 100% - 63% 82%
S.10
# Samples 145 27 21 100 63 27 - 4 - 30 417
% Exceed 85% 83% 0% 89% 80% 81% - - - 61% 81%
W.10-11
# Samples 109 18 2 75 118 27 - - - 44 393
% Exceed 88% 66% 38% 87% 85% 88% - 100% 0% 60% 78%
Totals
# Samples 1989 769 683 1461 974 441 - 4 17 479 6817

40
limits. The Hollywood and San Gabriel basins displayed matching patterns between their
respective percentages of samples exceeding the Basin Plan limits and the number of
samples collected each season, where an increase or decrease in percentage was coupled
with a respective comparable increase or decrease in the number of samples. This pattern
indicates that the number of samples and their spatial distribution could have an impact
on the percentage of samples exceeding the respective Basin Plan limits.
The percentages TDS samples exceeding the basin limits have gradually
diminished in three of the four basins (Central, West Coast and San Fernando basins)
with the highest percentages over the 10-year monitoring period (Figure 7). These three
basins also exhibited varying numbers of samples collected per season, which could be a
contributing factor to the decrease in percentage of samples exceeding the TDS Basin

Figure 7: The percentage of TDS samples exceeding the respective Basin Plan limits, during each season,
in the seven analyzed basins.

41
Plan limits. To gain a better understanding if the varying numbers of samples per season
may help to explain the decreasing trend in these three basins, a spatiotemporal analysis
was completed. Due to its high percentage of samples exceeding the Basin Plan limit and
its highest number of samples collected during the 10-year monitoring period, the Central
basin was selected for this analysis (Figure 8). The spatiotemporal analysis shows that
samples have been collected in a more dispersed pattern across the basin in recent years
and this fact, coupled with the consistency of samples exceeding the limit displayed in
Figure 8, suggest that the denser sampling gives a more accurate picture of groundwater
quality and that the TDS groundwater quality may be improving. Additional
spatiotemporal analyses completed for the San Fernando and West Coast basins (not
shown) displayed a similar dispersed pattern in recent years coupled with an increase in
consistency in the sampling size, additionally supporting that the larger sampling size in
recent years is providing an increasingly accurate picture of the TDS groundwater
pollution in these three basins.
Overall, the San Gabriel basin had the worst salt constituent readings during the
10-year period, containing the highest percentages of samples exceeding the respective
Basin Plan limits for chloride and TDS, and the second highest percentage of samples
exceeding the respective Basin Plan limits for sulfate. The San Gabriel basin also
displayed increasing percentages of samples exceeding the respective Basin Plan limits
for the same three salt constituents over the 10-year period. The Hollywood, Central,
West Coast and Santa Clara basins also displayed a large and sometimes increasing
fraction of readings for these salt constituents exceeding the respective Basin Plan limits.
42

Figure 8: Spatial distribution of TDS samples in the Central basin, during each season.
43
The Hollywood basin exhibited an increasing trend in the percentage of samples
exceeding the respective Basin Plan limits for both chloride and TDS; and the Central,
West Coast and Santa Clara basins were all in the highest groups of samples exceeding
the respective Basin Plan limits for two of the analytes (Central, boron and TDS; West
Coast, chloride and TDS; Santa Clara, boron and sulfate). While number and spatial
pattern of sampling locations could have affected the high percentages observed, it is
likely that high salt constituent concentrations are also contributing to the trend. The
only basin to exhibit a decreasing trend for multiple salt constituents was the San
Fernando basin, which was observed to have decreasing percentages of samples
exceeding the respective Basin Plan limits for two of the four analytes (chloride and
TDS). While variations in sampling numbers and locations during each season in the San
Fernando basin could have contributed to the decrease in percentage, it is likely that the
concentrations of both salt constituents are falling and that the groundwater quality in the
San Fernando basin is improving.
4.1.2 Nutrient Constituents
A total of 3,336 nitrite-nitrogen (NO
2
-N) samples have been collected in Los
Angeles County since November 2001. The nitrite-nitrogen readings were the lowest of
any of the analytes analyzed in this thesis study, with just 1% of the samples exceeding
the Basin Plan limit. No nitrite-nitrogen sampling in the Hollywood, Raymond, Russell
and Malibu basins included continuous samples across the 10-year period; therefore,
these four basins were excluded from further analysis (Table 8). In the remaining six
basins, the Central basin was the only basin with continuous sampling for the entire study
44
Table 8: The number and fractions of nitrite-nitrogen samples exceeding the Basin Plan limit, in each
basin, during each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San
Gabriel
Raymond
Russell
Malibu
Santa
Clara
L.A.
County
% Exceed 0% 0% 8% - 0% - - - - - 6%
W.01-02
# Samples 2 4 40 - 8 - - - - - 54
% Exceed 0% - 0% 0% 0% - - - - - 0%
S.02
# Samples 1 - 20 2 7 - - - - - 30
% Exceed 0% 0% 0% 0% - - - - - - 0%
W.02-03
# Samples 12 2 1 11 - - - - - - 26
% Exceed 0% 0% 0% - - - - - 0% - 0%
S.03
# Samples 3 14 19 - - - - - 5 - 41
% Exceed 0% 0% - 10% - - - - 0% - 4%
W.03-04
# Samples 3 17 - 21 - - - - 6 - 47
% Exceed 0% 0% - 5% - - - - 0% - 2%
S.04
# Samples 1 15 - 22 - - - - 3 - 41
% Exceed 3% 0% 0% 0% - 0% - - 0% 0% 2%
W.04-05
# Samples 105 13 20 17 - 8 - - 3 30 196
% Exceed 0% 0% 0% 17% 0% 0% - - - 0% 2%
S.05
# Samples 35 7 56 24 13 3 - - - 30 168
% Exceed 0% - 0% 0% 3% 0% - - - 0% 1%
W.05-06
# Samples 36 - 53 72 68 3 - - - 30 262
% Exceed 2% - 0% 26% 0% 0% - - - 0% 2%
S.06
# Samples 90 - 149 19 131 7 - - - 34 430
% Exceed 2% - 0% 5% 0% 0% - - - 0% 1%
W.06-07
# Samples 44 - 48 19 74 8 - - - 34 227
% Exceed 0% - 0% 2% 0% 0% - - - 0% 0%
S.07
# Samples 36 - 42 42 109 7 - - - 34 270
% Exceed 2% 0% 3% 0% 0% 0% - - - 0% 1%
W.07-08
# Samples 53 10 34 6 96 8 - - - 34 241
% Exceed 0% 0% 0% 32% 0% 0% - - - 0% 5%
S.08
# Samples 71 11 6 37 93 9 - - - 32 259
% Exceed 0% 0% 0% 2% 1% 0% - - - 0% 1%
W.08-09
# Samples 57 14 6 53 102 9 - - - 14 255
% Exceed 2% 0% 0% 0% 0% 0% - - - 0% 0%
S.09
# Samples 45 8 22 21 74 8 - - - 32 210
% Exceed 0% - 0% 0% 0% 0% - - - 0% 0%
W.09-10
# Samples 67 - 38 24 44 6 - - - 32 211
% Exceed 0% 0% 0% 0% 1% 0% - - - 0% 1%
S.10
# Samples 27 2 2 55 83 5 - - - 26 200
% Exceed 0% 0% - 0% 0% 0% - - - 0% 0%
W.10-11
# Samples 20 1 - 23 78 6 - - - 40 168
% Exceed 1% 0% 1% 6% 0% 0% - - 0% 0% 1%
Totals
# Samples 708 118 556 468 980 87 - - 17 402 3336

45
period, the other five basins all began continuous sampling at different times (West
Coast, winter 2003-2004; Santa Monica, San Gabriel and Santa Clara, winter 2004-2005;
San Fernando, summer 2005). None of the basins analyzed demonstrated a winter and
summer seasonal trend across the 10-year period. Overall, the percentage of samples
exceeding the Basin Plan limit was very low in each basin. Three basins (San Fernando,
San Gabriel and Santa Clara) displayed an overall average of zero percent of samples
exceeding the Basin Plan limit, while the Central, Santa Monica and West Coast basin
had percentages of one, one, and six percent, respectively. The ranges varied from 0-3%
in the Central and San Fernando basins over the 10-year period, unlike the Santa Monica
and West Coast basins which exhibited higher fluctuations of percentages of samples
exceeding the Basin Plan limit from season to season, ranging from 0 to 8% in the Santa
Monica basin and 0 to 33% in the West Coast basin. Additionally, the four basins with
the largest percentages of samples exceeding the Basin Plan limit were the four sub-
basins of the Los Angeles Coastal Plain basin. The presence of higher readings of nitrite-
nitrogen in the Los Angeles Coastal Plain sub-basins can presumably be attributed to
local sources of groundwater pollution that are found in these coastal basins, such as
higher numbers of leaking sewers or larger volumes of urban runoff.
A total of 4,839 samples have been collected for nitrate (NO
3
) in Los Angeles
County since November 2001; 8% of these samples were found to exceed the Basin Plan
limit. During this time the Central, West Coast and San Fernando basins were the only
basins with sufficient continuous data to analyze trends (Table 9). None of these basins
displayed a winter and summer trend. The San Fernando basin displayed the highest
46
Table 9: The number and fractions of nitrate samples exceeding the Basin Plan limit, in each basin, during
each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San
Gabriel
Raymond
Russell
Malibu
Santa
Clara
L.A.
County
% Exceed 9% - 8% 1% 19% 0% - - - - 8%
W.01-02
# Samples 142 - 66 114 72 22 - - - - 416
% Exceed 7% 0% 0% 1% 33% 3% - - - - 8%
S.02
# Samples 133 7 55 98 64 33 - - - - 390
% Exceed 8% 0% 0% 1% 0% 7% - - - - 5%
W.02-03
# Samples 185 10 4 101 42 29 - - - - 371
% Exceed 4% 0% 0% 0% 3% 25% - - - - 3%
S.03
# Samples 142 9 6 128 71 8 - - - - 364
% Exceed 3% 0% 0% 0% 9% 10% - 0% - - 4%
W.03-04
# Samples 156 29 6 100 65 31 - 9 - - 396
% Exceed 5% 0% 0% 10% 2% 15% - 0% - 17% 6%
S.04
# Samples 118 11 19 77 56 13 - 18 - 6 318
% Exceed 1% 0% 0% 6% 3% 25% - 0% - - 4%
W.04-05
# Samples 69 3 12 31 63 8 - 9 - - 195
% Exceed 4% 0% 0% 0% 3% 50% - - - - 4%
S.05
# Samples 109 3 12 35 29 4 - - - - 192
% Exceed 4% 0% 0% 8% 3% 50% - - - - 5%
W.05-06
# Samples 151 3 5 61 35 4 - - - - 259
% Exceed 7% 0% - 7% 6% 50% - - - - 8%
S.06
# Samples 101 3 - 43 35 4 - - - - 186
% Exceed 4% - - 8% 13% 20% - - - - 6%
W.06-07
# Samples 141 - - 62 40 5 - - - - 248
% Exceed 11% 0% 65% 5% 71% - - - - - 26%
S.07
# Samples 105 3 20 42 38 - - - - - 208
% Exceed 13% - - 5% 34% - - - - - 15%
W.07-08
# Samples 87 - - 40 35 - - - - - 162
% Exceed 15% 0% 0% 8% 29% - - - - - 14%
S.08
# Samples 111 3 21 48 35 - - - - - 218
% Exceed 15% 0% 0% 16% 35% - - - - - 16%
W.08-09
# Samples 80 18 21 81 37 - - - - - 237
% Exceed 7% 0% 0% 8% 44% - - - - - 18%
S.09
# Samples 54 3 6 61 55 - - - - - 179
% Exceed 0% 0% 0% 13% 30% 0% - - - - 13%
W.09-10
# Samples 32 7 10 71 43 2 - - - - 165
% Exceed 0% 0% 0% 3% 6% 0% - 0% - - 3%
S.10
# Samples 48 10 9 34 47 8 - 4 - - 160
% Exceed 2% 0% 0% 6% 0% 0% - - - - 2%
W.10-11
# Samples 60 7 9 48 46 5 - - - - 175
% Exceed 7% 0% 6% 5% 17% 11% - 0% - 17% 8%
Totals
# Samples 2024 129 281 1275 908 176 - 40 - 6 4839

47
percentage of samples exceeding the Basin Plan limit. Overall, the percentages of
samples exceeding the Basin Plan limit were relatively low from November 2001 until
the summer of 2007 when the percentage spiked to 71%. Since the summer 2007 season
the fraction has declined to zero percent of samples exceeding the Basin Plan limit in the
winter 2010-2011 season. The Central and West Coast basins displayed comparable
trends where the height of the percentage of samples exceeding the Basin Plan limit in
each basin was reached in the winter 2008-2009 season; which has since declined
through the winter 2010-2011 season. The large sampling effort recorded throughout the
study period within these three basins suggests that the decreasing trend in recent years is
due to a decrease in nitrate concentrations. Since these basins are also widely dispersed
across Los Angeles County, the decrease displayed in all three basins may be due to a
real decrease in rainfall or some other region-wide factor that affects nitrate
contamination of groundwater.
A total of 28,407 samples have been analyzed for nitrate-nitrogen (NO
3
-N) in Los
Angeles County since November of 2001; 14% of these samples exceeded the Basin Plan
limit. During this time period the sampling effort in the Raymond and Malibu basins was
too sparse to determine trends in groundwater quality (Table 10). A winter and summer
seasonal trend was not found in any of the eight analyzed basins. The San Fernando
basin contained the highest percentage of samples (25%) exceeding the Basin Plan limit.
Meanwhile, the Russell and Santa Clara basins, which did not begin continuous sampling
until the winter 2004-2005 season, contained two of the lowest percentages of the
samples exceeding the Basin Plan limit with only three and one percent, respectively. A
48

Table 10: The number and fractions of nitrate-nitrogen samples exceeding the Basin Plan limit, in each
basin, during each season.
Los Angeles Coastal Plain
Season

Central
Holly-
wood
Santa
Monica
West
Coast
San
Fernando
San
Gabriel
Raymond
Russell
Malibu
Santa
Clara
L.A.
County
% Exceed 10% 13% 0% 18% 37% 0% - - - - 15%
W.01-02
# Samples 346 15 15 163 83 4 - - - - 626
% Exceed 10% 13% 8% 11% 26% 17% - - - - 13%
S.02
# Samples 516 23 80 208 141 12 - - - - 980
% Exceed 8% 4% 8% 15% 18% 0% - - - - 10%
W.02-03
# Samples 601 45 77 267 131 29 - - - - 1150
% Exceed 8% 11% 8% 17% 24% 6% - - 0% 0% 13%
S.03
# Samples 442 44 93 197 177 36 - - 5 3 997
% Exceed 12% 0% 2% 11% 16% 0% - 14% 0% 67% 12%
W.03-04
# Samples 505 28 49 228 173 31 - 7 6 3 1030
% Exceed 10% 0% 10% 13% 19% 0% - - 0% - 11%
S.04
# Samples 542 45 93 231 151 38 - - 3 - 1103
% Exceed 14% 5% 3% 10% 24% 8% - 11% 0% 0% 12%
W.04-05
# Samples 757 66 143 367 185 88 - 28 3 30 1667
% Exceed 16% 4% 4% 10% 24% 13% - 4% 0% 0% 14%
S.05
# Samples 701 52 169 457 316 115 - 25 5 30 1870
% Exceed 14% 9% 5% 10% 26% 16% - 9% 0% 0% 14%
W.05-06
# Samples 784 44 164 511 329 132 - 34 7 30 2035
% Exceed 12% 3% 6% 16% 24% 16% - 3% 0% 0% 14%
S.06
# Samples 741 74 241 464 450 132 - 34 7 38 2181
% Exceed 13% 0% 13% 18% 28% 14% - 0% 0% 0% 16%
W.06-07
# Samples 748 38 151 392 389 133 - 61 5 34 1951
% Exceed 9% 2% 16% 20% 33% 13% - 0% 0% 0% 17%
S.07
# Samples 646 60 138 441 436 148 - 40 12 34 1955
% Exceed 10% 0% 17% 18% 30% 15% - 0% 0% 0% 16%
W.07-08
# Samples 768 48 145 436 424 152 - 44 8 34 2059
% Exceed 11% 0% 18% 17% 21% 12% 0% 0% 0% 0% 14%
S.08
# Samples 766 32 91 360 474 124 9 74 7 32 1969
% Exceed 10% 1% 13% 16% 26% 20% - 5% 0% 0% 15%
W.08-09
# Samples 850 71 106 383 525 147 - 74 8 32 2196
% Exceed 7% 0% 23% 23% 28% 15% 0% 0% - 0% 15%
S.09
# Samples 473 23 65 230 188 98 8 37 - 32 1154
% Exceed 10% 0% 6% 15% 29% 28% 0% 3% - 0% 14%
W.09-10
# Samples 627 52 84 290 236 60 8 39 - 32 1428
% Exceed 8% 6% 18% 18% 21% 20% - 0% - 0% 14%
S.10
# Samples 378 17 44 214 228 49 - 18 - 26 974
% Exceed 8% 0% 10% 16% 21% 34% 0% 3% - 2% 13%
W.10-11
# Samples 400 20 31 220 288 41 7 31 - 44 1082
% Exceed 11% 3% 9% 15% 25% 15% 0% 3% 0% 1% 14%
Totals
# Samples 11591 797 1979 6059 5324 1569 32 546 76 434 28407

49
decreasing trend in the percentage of samples exceeding the Basin Plan limit was
observed in the Hollywood and Russell basins, while the San Gabriel basin exhibited an
increasing trend (Figure 9). However, each of these basins had widely varying sample
numbers during each season, which may have contributed to the identified increasing and
decreasing trends.

Figure 9: The percentage of nitrate-nitrogen samples exceeding the Basin Plan limit, during each season,
in the eight analyzed basins.
A total of 734 samples have been analyzed for nitrite-nitrogen plus nitrate-
nitrogen (NO
2
-N + NO
3
-N) in Los Angeles County since November 2001; 14% of these
samples have exceeded the Basin Plan limit. However, none of the 10 basins contained
sufficient data to identify spatiotemporal trends. Therefore, nitrite-nitrogen plus nitrate-
nitrogen data was not further analyzed in this thesis study.
Overall, the San Fernando basin contained the highest percentages of samples
exceeding the Basin Plan limits for two of the three analyzed nutrient constituents with
50
17% of nitrate samples and 25% of nitrate-nitrogen samples exceeding the respective
Basin Plan limits. Additionally, the West Coast basin displayed the highest percentage of
samples exceeding the Basin Plan limit for nitrite-nitrogen (6%) and the second highest
percentage of samples exceeding the Basin Plan limit for nitrate-nitrogen (15%). Overall,
the nutrient constituents changed little over the 10-year time frame. Both nitrate and
nitrate-nitrogen exhibited small decreases over the 10-year period in two basins each
(nitrate, Central and West Coast basins; nitrate-nitrogen, Hollywood and Russell basins).
The number of samples varied across seasons in the Hollywood and Russell basins, but
the sample effort in the Central and West Coast basins was relatively consistent. The
latter provides a stronger argument for the decreasing trend being tied to a real decrease
in the nitrate concentration in these basins. Apart from these trends, all of the other
constituents in each of the analyzed basins exhibited no clear trend.
4.2 Additional Groundwater Spatial Analyses
In addition to the spatiotemporal analysis completed for each constituent, two
additional spatial analyses were conducted on the Los Angeles County groundwater data:
the first examined the relationship between the percent of samples exceeding the
respective Basin Plan limits for salt and nutrients and the depth to groundwater and the
second examined the percentage of samples exceeding the respective Basin Plan limits
for salts and the distance from the coastline. The depth of the groundwater table surface
has a recognized inverse correlation to the level of groundwater pollution in a basin (Ahn
and Chon, 1999; Eckhardt and Stackelburg, 1995; Gardner and Vogel, 2005; Hudak,
1999, 2000; Pacheco and Cabrera, 1997; Tesoriero and Voss, 1997). Shallow
51
groundwater tables collect water more recently infiltrated from the surface, providing less
time for the soil to filter the groundwater pollutants. Deeper groundwater aquitards
collect water that has traversed a longer flow path and provided more time for
groundwater pollutants to be filtered out. In order to understand at what depth the
samples exceeding the plan limits for each constituent are located, the total depth range
was divided into five equal sample classes. The percentage of samples with values
exceeding the respective Basin Plan limits was analyzed for each depth category for each
constituent (Table 11).
Table 11: The number and fractions of samples exceeding the respective Basin Plan limits for each
constituent at each equal sampled depth.

-0.91
to 14
ft.
14.01
to
24.47
ft.
24.48
to
35.57
ft.
35.58
to
60.56
ft.
60.57
to
780.47
ft.
No
Data
Total
% Exceed 21% 13% 8% 12% 12% 6% 11%
Boron
# Samples 211 383 594 266 1025 228 2707
% Exceed 30% 20% 40% 41% 35% 24% 35%
Chloride
# Samples 517 752 1761 1989 2744 866 8629
% Exceed 43% 45% 40% 31% 25% 32% 37%
Sulfate
# Samples 6410 8486 7745 7603 5889 1152 37285
% Exceed 78% 83% 83% 71% 74% 93% 78%
TDS
# Samples 925 878 1141 1369 2135 369 6817
% Exceed 3% 0% 0% 1% 1% 4% 1%
Nitrite-N
# Samples 111 173 337 682 1531 502 3336
% Exceed 9% 7% 6% 6% 11% 24% 8%
Nitrate
# Samples 768 1013 1304 899 687 168 4839
% Exceed 14% 12% 12% 15% 19% 13% 14%
Nitrate-N
# Samples 5520 6603 5428 5689 4495 672 28407
% Exceed 12% 14% 10% 18% 61% 17% 14%
Nitrite-N +
Nitrate-N
# Samples 138 267 240 44 33 12 734

The nitrate-nitrogen and the nitrite-nitrogen plus nitrate-nitrogen constituents
increased in percentage of samples exceeding the respective Basin Plan limit with
52
increasing depth class. The chloride and nitrate constituents displayed fluctuating
percentages of samples exceeding the respective Basin Plan limits, however, both
chloride and nitrate showed an overall increasing percentage of samples exceeding the
respective Basin Plan limits with increasing depth class. The sample sizes for each of
these constituent varied significantly. Overall, nitrate-nitrogen and nitrite-nitrogen plus
nitrate-nitrogen decreased in sample size with increasing depth class, while the chloride
sample size increased with increasing depth class, and the nitrate constituent experienced
an increase and then decrease in sample size with increasing depth.
Since the nitrate-nitrogen constituents had relatively the highest number of
samples and a similar sample supply across the five depth classes, a spatial analysis was
conducted in order to investigate if the location of the samples influenced the increasing
concentrations that were exhibited with increasing depth (Figure 10). The Central and
Hollywood basins contained sampling and evenly spatially distributed samples at all of
the depth sections. The San Fernando, San Gabriel, West Coast and Santa Monica basins
displayed an increase in spatial distribution across each basin in the deeper sections. This
change in the distribution of groundwater sampling in the deeper sections could be
influencing the increase in nitrate-nitrogen samples that are exceeding the respective
Basin Plan limits but it is likely that nitrate-nitrogen concentration is increasing with
increasing depth class.
Meanwhile, the boron, sulfate, TDS and nitrite-nitrogen constituents show
decreases in percentages of samples exceeding the respective Basin Plan limits with
depth (Table 11). All four constituents showed inconsistent sampling numbers with each
53

Figure 10: The spatial distribution of nitrate-nitrogen samples in each of the five depth classes.
depth class. Due to the higher sampling numbers, the sulfate data was analyzed further to
determine any trends and clues that might explain the decrease in fraction of samples
exceeding the respective Basin Plan limits with increasing depth (Figure 11). Across
54
each of the basins it is clear that in the deepest two sections, the sampling is more widely
distributed. This trend is especially evident in the Santa Clara, San Gabriel and West
Coast basins. Looking more closely at the pattern of samples not exceeding the

Figure 11: The spatial distribution of sulfate samples in each of the five depth classes.
55
respective Basin Plan limits, this increase in the spatial distribution of sampling locations
is the most likely explanation for the decrease in the percentage of sulfate samples
exceeding the respective Basin Plan limits with groundwater depth.
The distance of a site to the coastline can have an influence on the salt
constituents that are measured in a sample. Since salt-water intrusion is a problem that
only affects basins close to the coastline, the Central, Hollywood, Santa Monica, West
Coast and Malibu basins were used for this portion of the analysis. However, as
displayed in the spatiotemporal analysis tables (Tables 4-10); the Malibu basin did not
contain adequate sample sizes to provide a significant contribution to the analysis.
Therefore, only the four sub-basins of the Los Angeles Coastal Plan basin were analyzed
comparing the distance to the coastline to the percentage of samples exceeding the
respective Basin Plan limits for each of the four salt constituents (Table 12). With
increasing distance from the coastline, the percentage of samples exceeding the
respective Basin Plan limits increased for three of the four salt constituents (boron,
Table 12: The numbers and fractions of samples exceeding the respective Basin Plan limits for each salt
constituent at various distances from the coastline.
Nearest Near Mid Far Farthest Total
All LA
Basins
Total
% Exceed 6% 14% 9% 34% - 12% 11%
Boron
# Samples 491 509 287 127 0 1414 2707
% Exceed 35% 45% 32% 31% 7% 37% 35%
Chloride
# Samples 1938 1990 1792 218 43 5981 8629
% Exceed 28% 36% 43% 38% 14% 35% 37%
Sulfate
# Samples 7676 9665 5654 3882 465 27342 37285
% Exceed 69% 85% 72% 95% 14% 77% 78%
TDS
# Samples 1708 2054 844 253 43 4902 6817

56
sulfate and TDS), until the farthest distance category where the percentages dropped
dramatically in each of the basins. The decline in sampling number may explain some of
this decrease. The percentage of samples exceeding the chloride Basin Plan limit
decreased with distance, suggesting that saltwater intrusion may still contribute to higher
chloride levels at sites closer to the coast.
57
Chapter 5 – Conclusions
5.1 Groundwater Quality in Los Angeles County
Sulfate and nitrate-nitrogen were the two constituents monitored most intensely
with 37,285 and 28,407 samples, respectively, collected during the study period. The
salts are routinely higher than the nutrients in terms of the percentage of samples
exceeding the respective Basin Plan limits. The nutrient constituents have been sampled
less frequently (nitrate, 4,839 samples; nitrite-nitrogen, 3,336 samples; and nitrite-
nitrogen plus nitrate-nitrogen, 734 samples) and have much lower percentages of samples
exceeding the respective plan limits (nitrate-nitrogen, 14%; nitrite-nitrogen, 14%; nitrate,
8%; nitrite-nitrogen, 1%). Therefore, the noted sources of salt constituents are most
likely occurring in higher volumes in Los Angeles County than the noted sources of
nitrogen constituents. The TDS, sulfate and chloride measurements exceeded the
respective Basin Plan limits 78%, 37% and 35% of the time, respectively. Industrial
effluent is the most commonly noted source of these three constituents, and therefore
could be the leading contributor to groundwater pollution in Los Angeles County.
The Central Basin experienced the largest sampling effort with 34,552 samples
collected during the 10-year study period. The West Coast and San Fernando basins
were second and third in terms of sample effort with 19,799 and 17,511 samples
collected, respectively. The number of samples correlate to the size of the basins: the
Central basin is the largest basin (177,000 acres), the San Fernando and West Coast are
the third and fourth largest basins covering 145,000 and 91,300 acres, respectively.
Additionally, the variations in sampling in each basin could also be attributed to the
58
population distribution in the basin area. The higher volume of population would
contribute to a larger number of underground storage tanks, site clean-ups and land
disposal sites that would have been monitored and included in the Geotracker data set
utilized in this thesis study. This additional analysis could provide insight to the potential
relationship between the limited distribution of sampled sites in San Fernando, San
Gabriel and Raymond groundwater basins and the distribution of the population across
these basins.
The Geotracker database consists of data driven by types of land use (open and
closed underground storage tanks, site clean-up programs and land disposal sites) and the
related permits required for these uses. The primary purpose of each permit holder’s
monitoring requirements that are catalogued and reported in Geotracker is to help the Los
Angeles Regional Water Quality Control Board discover and track substantial site
specific groundwater quality problems as they develop. A secondary purpose of the
Geotracker database may be to assist the Regional Board in monitoring the overall
groundwater quality conditions across Los Angele’s 10 groundwater basins. While the
Geotracker database and permit holder monitoring program works well for the first
priority, the results of this thesis study show that the database does not support the task of
overall monitoring of groundwater quality across the county.
The results of the analysis show that it is difficult to clarify spatiotemporal trends
given that individual samples at specific locations were collected at different time
intervals and that the measurement locations are clustered around the permit holder sites.
These two qualities of the data collection approach coupled with the high levels of
59
variability in groundwater quality conditions that might be expected in space and time
meant that the Geotracker database provides insufficient support to make wider use of the
spatial interpolation and analysis tools available in ArcGIS and similar spatial analysis
software. The results reported for the Central basin TDS spatiotemporal analysis showed
that the varying spatial extent of sampling may be the reason for the identified decrease
in TDS percentage of samples exceeding the respective Basin Plan limits rather than an
actual decrease in the constituent that was measured. Meanwhile the figures and
accompanying text discussing the Hollywood chloride spatiotemporal analysis and the
San Gabriel spatiotemporal analysis show that while the limited spatial extent of the
samples did not allow for a trend to be recognized across entire basins, the spatial
distribution did allow for trends to be seen in certain portions of selected basins.
Overall, no overarching spatial or temporal trends were uncovered in this thesis
study. Some basins were found to contain higher instances of constituents exceeding the
limits, such as the San Gabriel basin, which has the highest percentage of samples
exceeding the respective Basin Plan limits for both chloride and TDS and the second
highest percentage of samples exceeding the Basin Plan limits for sulfate. However, the
individual constituents varied from basin to basin in terms of their spatial and temporal
patterns. The lack of spatial and temporal trends across the basins could be a result of the
limitations of the dataset that was analyzed, or the need for additional analysis at different
scales or utilizing different methods.
60
5.2 Limitations of the Spatiotemporal Analysis
The data set obtained from the California Water Quality Control Board’s
Geotracker site had certain limitations that may have affected the spatial and temporal
patterns seen in this thesis study. First, the dataset does not contain samples that are
collected in a dispersed pattern across each basin, nor are they collected at uniform
depths, because the locations were limited by the locations of the permit holder sites.
Therefore it can be difficult to determine spatial and temporal patterns when the sampling
does not cover the entire basin and the same aquifers (i.e. depth). This was a notable
limitation in the San Fernando, San Gabriel and Raymond basins. Similarly, the
sampling in the dataset was not uniform over time and therefore it was difficult to
characterize the temporal patterns.
In addition to the sampling pattern, errors in the Geotracker dataset could have
stemmed from differences and mistakes in the collection and analysis protocols. The
samples included in this dataset were all collected and analyzed by different contractors
hired by the permit holders of the underground storage tanks, site clean-ups and land
disposal sites. While the California Water Quality Control Board specifies to the level of
accuracy to which the measurements must be completed, the sampling and analytical
procedures and protocols likely varied both between different contractors and with time
over the 10-year analysis period; these changes likely introduced different and
untraceable sources of error. There errors may have affected the percentage of samples
exceeding the respective Basin Plan limits, which would in turn affect the spatial and
temporal patterns observed in this thesis study. The extent of such problems is unknown.
61
5.3 Recommendations for Future Research
Some additional analysis could still be completed on the Geotracker dataset
utilized in this thesis study, from which it might be possible to uncover finer scale spatial
and temporal trends. Since no county level trends were observed, the analysis might
focus on the basin and sub-basin scales, and possibly specific clusters of samples sites.
The Geotracker samples were often clustered in small areas that had multiple samples, so
conducting analysis at this scale would allow for the utilization of every individual
sample and therefore might help to uncover spatial and temporal trends for the salt and
nutrient contamination.
Looking beyond these incremental steps, a more complete and thoughtful dataset
would be needed to create a true understanding of the complex sources and pathways of
the salt and nutrient constituents in Los Angeles County’s groundwater basins. This
dataset would contain uniformly collected data that was collected using a spatially
distributed sampling frame across each of the groundwater basins, and contains samples
taken at multiple groundwater depths. This dataset would allow for a better
understanding of the spatial patterns across the San Fernando, San Gabriel and Raymond
groundwater basins, for example, since they currently lack good spatial distribution of
samples in the Geotracker dataset. Additionally, this dataset would allow for a better
representation of the groundwater quality in each of the aquifers in each of the basins.
This dataset would allow for more than just a spatial and temporal analysis but would be
able to construct an interpolated surface for each aquifer that could be used to
characterize the horizontal and vertical distributions of groundwater constituents in Los
62
Angeles County. Additional information that may advance our understanding of the
complex sources and pathways of groundwater pollution include the locations of
penetrable and impenetrable surfaces, the sewer systems, and groundwater flow models
that account for the geology of the alluvium in each of the basins in Los Angeles County.
These kinds of data might be combined in a variety of modeling frameworks and the
monitoring data would be used to calibrate and validate the models with the overall goal
of tracking the sources and best means of prevention and remediation of groundwater
contamination in Los Angeles County over time.
63
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Abstract (if available)

Abstract Salts and nutrients are common contaminants in urban groundwater systems, and at certain levels these pollutants have been associated with adverse effects on agriculture, corrosion and mineral deposits on industrial piping, a decrease in the drinkability of water, and serious health problems. Groundwater pollution can stem from both natural and anthropogenic sources and given the high costs of remediation, groundwater managers are tasked with monitoring groundwater contamination and controlling its sources. With its large population, close proximity to the coastline and arid climate, Los Angeles County provides an important study area for the spatial and temporal analysis of salt and nutrient constituents across each of its 10 groundwater basins. ❧ This thesis study utilizes the California Regional Water Quality Control Board data set consisting of groundwater quality samples drawn from underground storage tanks, site clean-up programs and land disposal sites to determine the spatiotemporal patterns across each basin. Results show that no spatiotemporal pattern was recognized, except that the salt constituents routinely exceeded the respective Basin Plan limits (unlike the nutrient constituents). In the end, more conclusive results could be determined with additional analysis and modeling that was better designed for sample collection and better controlled over the locations and depths at which the samples were taken.

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Asset Metadata

Creator MacGillivray, Holly Marie (author)

Core Title Spatiotemporal patterns of salt and nutrient contamination in Los Angeles County's groundwater basins

School College of Letters, Arts and Sciences

Degree Master of Science

Degree Program Geographic Information Science and Technology

Publication Date 07/24/2012

Defense Date 06/14/2012

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag GIS,ground water quality,Los Angeles County,nutrients,OAI-PMH Harvest,salts,spatiotemporal patterns

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Wilson, John P. (committee chair), Hastings, Jordan T. (committee member), Kemp, Karen K. (committee member)

Creator Email hmacgill@usc.edu,holly.macgillivray@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c3-62332

Unique identifier UC11289239

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