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Wadi Elmegenin artificial ground water recharge

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Wadi Elmegenin artificial ground water recharge

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Content WADI ELMEGENIN ARTIFICIAL GROUND WATER RECHARGE A Thesis Presented to the Faculty of the School of Engineering University of Southern California In Partial Fulfillment of the Requirements for the Degree Master of Science Civil Engineering (Water Resources) by Mohamed Ibrahim Matoug June 1975 UMi Number: EP41994 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMT Dissertation Publishing UMI EP41994 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest' — ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 \p & O , *75 H433 This thesis, w ritten by , Mohamed Ibrahim Matoug under the guidance of F acu lty Committee and approved by a ll its members, has been presented to and accepted by the School of E ngineering in p a rtia l fu lfillm e n t of the re quirements fo r the degree of Master of Science Civil Engineering (Water Resources) C o ^ p.tisurr ox ■ <£3n B D a te L9I5. F a cu lty C om m ittee Chairm an ACKNOWLEDGEMENTS The author wishes to express his deep gratitude to Professor Stanley S. Butler for his continuous advice and valuable guidance,, without which this thesis could not have been completed; Special thanks are due to the following persons for their contributions toward the completion of this proj ect: Professor Richard H. Merriam, Department of Geology, for his valuable advice. Professor Jiin-Jen Lee, Department of Civil Engineering, for his valuable advice. ABSTRACT The Wadi-Elmegenin Dam was built in 19 7 0 to control the flooding caused by the intense winter storms. As a result of building the dam, the natural infiltrated water was stopped from feeding the ground'water reservoir down stream. This cut-off was estimated to be approximately two million cubic meters annually. - In this thesis, different recharge methods are dis cussed in detail. The natural stream-bed basin method is chosen as the most suitable. Water will be carried from the reservoir outlet in a closed conduit to the irrigation area where about 34% of the annual runoff will be used to irrigate 4 5 0 acres of land. The extra water, about 3 3%, will flow through the wadi bed and will be sent to a selected recharge area near Ben Ghishir. The advantage of this method is that during extremely dry years the water can be used solely for irrigation. In wet years, when the average runoff is more than that re quired for the irrigated area, the water will be diverted to the recharge system. TABLE OF CONTENTS ACKNOWLEDGEMENTS . ii ABSTRACT iii LIST OF TABLES vi LIST OF FIGURES viii LIST OF SYMBOLS x Chapter I. INTRODUCTION 1 II. WADI-ELMEGENIN HYDROLOGY A. Description of the Catchment Area 3 B. Evaporation from Water Surfaces*. 6 C. Precipitation 16 D. General Form of Regression Model Used to Simulate Runoff 2 5 III. GROUND WATER HYDROLOGY A. Occurrence * *........... 38 B. Water Movement ....... 3 8 C. Source of Ground Water in the Wadi Elmegenin Area 5 3 D. Ground Water Movement in the Wadi Elmegenin Area 54- E. Water Depth in the Wadi Area •• 54- F. Fluctuationsiin the Wadi Area 5 6 G. Ground Water Use in the Wadi Area 5 6 IV* ARTIFICIAL STORAGE OF GROUND WATER A. Direct Benefits of Artificial Recharge 57 B. Selection of Recharge Sites . . gg i v TABLE OF CONTENTS, Continued C. Methods of Recharge ......... 60 D. Hydraulic Analysis 66 V. YEARLY SURFACE WATER BALANCE IN THE WADI ELMEGENIN RESERVOIR ... ... 6 9 VI. IRRIGATION PROJECT A. Soil Study at the Downstream End of the Reservoir ...... 72 B. Consumptive Use ............... 91 C. Irrigation System ............. 92 VII. GROUND WATER STORAGE PROJECT A. Annual Runoff ................. 99 B. Silt Content in the Surface Water... 10 2 VIII. CONCLUSION 115 REFERENCES • * — 111 v LIST OF TABLES 2-1 Average Annual Temperature in °C over a 23-Year Span (1950-1972) 7 2-2 Average Monthly Temperature in °C over a 23-Year Span (1950-1972) g 2-3 Average Maximum Temperature in °C over a 17-Year Span (1950-1966) . .................. g 2-4 Average Minimum Temperature in °C over a 17-Year Span (1950-1966) 10 2-5 Total Monthly Evaporation .................. 22 2-6 Evaporation Data for 39 Storms 24 2-7 Yearly Evaporation in Percent ............. 25 2-8 Data for Double Mass Curve .............. 2 8 2-9 Data Used to Calculate the Runoff Coefficient 30 2-10 Runoff Coefficients for Different Series ... 32 2-11 Annual Runoff in Millimeters, Series Nos. 1-8. 32 2-12 Annual Runoff in Millimeters, Series Nos. 9-12 34 2-13 Annual Runoff in Millimeters for Series No. 8 36 5-1 Annual Runoff and Losses ...... 70 6-1 Soil Texture of Al-Khitnah Area ......... 7 5 6-2 Soil Physical Properties of Al-Khitnah Area 76 6-3 Soil Chemical Properties of Al-Khitnah Area 77 6-4 Soil Texture of Hosh Area 81 6-5 Soil Physical Properties of Hosh Area ... 82 vi LIST OF TABLES, Continued 6-6 Soil Chemical Properties of Hosh Area ..... 83 6-7 Soil Texture' of Bu-Argub Area...... ............. 87 6-8 Soil Physical Properties of Bu-Argub Area .. 8 8 6-9 Soil Chemical Properties of Bu-Argub Area .. 8 9 6-10 Seasonal Consumptive Use Coefficient (K) .. 96 6-11 Mean Monthly Temperature, Percent of Day Light, Consumptive Use Factor, and Computed Consumptive Use...... ........................ 97 7-1.. Yearly Runoff in Cubic Meters of Wadi El-Megenin . 10 0 7-2 Runoff Classifications ..................... 105 7-3 Percent of Silt Content in the Runoff .. 105 vii list: of figures 1-1 Ground Water Decline in Ben Ghishir Area in Meters (19 6 0 - 19 7 2) 2 2.-1 Wadi Elmegenin Catchment Area ....... insert 2-2 Wadi Elmegenin Basin Isohyetal Map in Millimeters 18 2-3 Wadi Elmegenin Geological Map ......... insert 2-4 Isohyetal Map of Tripoli in.Millimeters . . insert 2-5 Daily Precipitation of Gharyan vs. Suq-Gmatah in Millimeters ........... 19 2-6 Monthly Precipitation of Gharyan vs. Wadi Elmegenin Catchment Basin in Millimeters.. 20 2-7 Double Mass Curve .................... 22 2-8 Precipitation - Elevation Relationship ,. 28 2-9 Duration Curve of Annual Runoff ..... 29 3-1 Typical Infiltration Capacity Curve of Undisturbed Soil 40 3-2 Infiltration-Time Curves for Sandy Loam Soil under Prolonged Submergence ..... 42. 3-3 Effect of Gypsum and Calcium Chloride on Infiltration Rate 44 3-4 Effect of Cotton-Gin Trash on Infiltration Rate ,.. 46 3-5 Effect of Mechanical Disturbance of a Soil on the Infiltration Rate , . . . . . . . . . 48 3-6 Effect of Interruptions in Spreading on Infiltration Rate .............. 50 viii LIST OF FIGURES, Continued 3-7 Infiltration Rate of Different Wadi.Profiles 3-8 Ground Water Contour Lines .................. insert 4-1 Aquifer Recharged through Trench Probolic Wetting Front ............... 61 4-2 Radial Flow from Recharge Well Penetrating (a) Free and (b) Confined Aquifers ..... 68 5-1 Reservoir Capacity Curve .............. 71 6-1 Soil Reconaissance Map ................ insert 6-2 Standard f-Capacity Curves of Al-Khitnah Area ..................... 78 6-3 Standard f-Capacity Curves of Hosh Area ... 84 6-4 Standard f-Capacity Curves of Bu-Argub Area 90 6-5 Irrigation Pipe Line ................. insert 6-6 Nomo-graph 98 7-1 Location of Check Profile and Hydrologic Stations ....... ....... 104 7-2 Typical Sediment Grain Size Distribution Curves .................. 107 7-3 Ground Water Elevation in the Recharge Area 7-4 Chlorine Content in the Ground Water in the Recharge Area........................... 110 7-5 Dike Arrangement for Recharging System ... 114 All page references to "insert” refer to oversize maps located in supplemental envelope. ix LIST OF SYMBOLS The following symbols are used in this thesis: A = cross-sectional area API = antecedent coefficient aQ , a-^ 3 = regression coefficient C = pan coefficient of evaporation d = pore diameter E = evaporation eQ = average saturation vapor pressure &2 - average vapor pressure at height Z above the water surface H = total head loss hQ = thickness of ground water aquifer hw = thickness of permeable material above ground water aquifer I = hydraulic gradient K = annual average class A pan coefficient k = specific permeability L = length in direction of flow m = confined aquifer saturated thickness Pg = gross rainfall P = runoff x LIST OF SYMBOLS, Continued p permeability Pe - effective porosity Q = volumetric rate of discharge q = discharge per unit length r - radial distance s = draw down t - average monthly temperature u = consumptive use M dynamic viscosity w = specific weight xi I. INTRODUCTION The increasing demand for ground water for domestic and industrial use and irrigation supply over the past two decades has caused a decline in water levels in many areas of Libya, especially in the coastal region. Other effects associated with the ground water overdraft are an adverse salt balance and sea water intrusion. Figure 1-1 shows the decline of the water level in the Ben Ghishir area. It is clear that the rate of de cline is accelerating. While in 1952 the average rate of water decline in the Ben Ghishir area was 0.5 meters per year, the decline reached 2 to 3 meters per year during 19 72. Part of this decline was caused by the building of a dam at an upstream mountain section. The problem of water level depression in the area may be solved by either decreasing the net usage or in creasing the recharge. Fortunately, the recharge can be increased by catching the runoff in surface reservoirs and spreading it on permeable deposits so that it will seep into the ground water basin. FIGURE 1-1: Ground Water Decline in the Ben Ghishir Area in Meters (.1960^72) - 10 20 r ~ ! -40 Year 19 60 61 62 63 64 65 , 66 , 67 68 69 70 71 72 II. WADI-ELMEGENIN HYDROLOGY A. Description of the Catchment Area Wadi Elmegenin flows from the south to the north: from the northern slopes of the mountains into the Medi terranean Sea. The wadi watercourse begins at 31°58T north latitude and 13°17T east longitude at an altitude of 908 meters above sea level. In the rocky valley near the end of the mountainous area, at an elevation of 249 meters A.S.L., the main dam was built in the wadi. The wadi estuary into the sea is situated at 32°53r north latitude and 13°09T east longitude in the western part of the city of Tripoli, as in Figure 2-1. The whole wadi catchment area has 9 5 2.83 square km, but the water comes from the upper part of the mountains. The mountainous part of the wadi catchment upstream from the main dam has 579.20 square km. The area consists of the following: Erodable sandy soil 102.8 square kilometers Arable land without erosion 43.4 Limestone and dolomite 341.4 Plateau with shallow soil covered by "esparto" grass 91.6 TOTAL 5 7 9.2 square kilometers The yearly precipitation in the mountainous part of the catchment area is 27 0 millimeters, on the average. An isohyetal map of the area is shown in Figure 2-2. Before the main dam was built, the wadi water percolated partly into the underground aquifer near Ben Ghishir. Now the flow is stopped by the dam, and the percolated water must be replaced by inflow from an artificial recharge arrange ment . 1. General geology Geologically, the' wadi' area is part of the Ge- fera Plain, and can be classified as listed below and as shown in Figure 2-3. Zone 1-1. Ras-Hamia Formation--middle upper Triassic, covering an area of 4.2 7 square km. This formation is mainly sandstone, sandy clay, and shale, with a total thickness of between 150 to 600 meters. Zone 2-2. Azizia Formation--middle upper Triassic, gener ally consisting of limestone and dolomitic limestone with shale interbeds. The average thickness is from 200 to 400 meters. The inner part gradually changes to the Ras- Hamia sandy formation. The area of this formation is 355.74 square km. Zone 3-3. Abu-Shaybah Formation— upper Triassic, consist ing of sandstone .occasionally criss-crossed with gravel strikes. This formation covers an area of 64.7 2 square km with a thickness of 15 0 meters. Zone 5-5. Kiklah Formation--lower Cretaceous, consisting of quartzitic sand or sandstone and red clay. This forma tion covers an area of 4.54 square km with an average thickness of 100 meters. Zone 6-6. Aintobi Formation--upper Cretaceous, consisting of hard massive limestone within layers of sand or clay. This formation covers an area of 70.95 square km with a range of thickness of 30 to 400 meters. Zone 7-7. Garyan Formation--upper Cretaceous, covering an area of 99.52 square km, and consisting of massive dolo mite starting at the top and a thin layer of dolomitic clay near the base. The thickness ranges from 5 0 to 10 0 meters. Zone 8-8~. Upper Miocene Formation--upper Miocene, contain ing marl, limestone, gypsiferous shale, clay, calcarous sand and conglomerate. This formation covers an area of 361 square km with an average thickness of 10 0 to 500 meters. Zone 9-ST. Superficial deposits--Quaternafy eolian deposits, coarse sand to clay with an average thickness of 30 to 80 meters, and covering an area of 3.7 square km. Zone 10-10’. Volcanic rocks--this formation is chiefly oli vine basalt of Tertiary age, covering an area of 5.6 9 square km. 2. Geologic structure There is one major fault in this area, south of i Ben Ghisir in a north-east direction. There is no evi- i dence of movement along this fault. Three smaller faults i are located south of Morabito.Bridge, south of Abu-Argub, ! and south of Amoit. All three faults lie in a south-east I 1 direction, and again there is no record of movement along j them. The faults in this area are considered inactive. t I 3. Temperature ! The average monthly temperatures, according to ; i registered data at the meteorological station at the site, j i are given for the observation period from 1950 to 1972. This continuous period of 2 3 years was considered suffi cient for reliable data on the temperature of the area • (see Table 2-1). The general characteristics of temperature variation in the wadi catchment area relate to the Mediterranean climatological zone. There are rather high temperatures with explicit annual variations, which cause intensive evaporation and transpiration. B. Evaporation from Water Surfaces In order to compute the losses due to evaporation in the reservoir of the main dam, several different methods were used. For Libyan climate, measurements of evapora- i tion from a Class A pan are used, but these data are | 6 ; TABLE 2-1 AVERAGE ANNUAL TEMPERATURE IN °C OVER A 23-YEAR SPAN (1950-1972) Average Annual Temperature No. Year in °C 1 1950 20 2 1951 20.9 3 1952 21.1 4 1953 20.2 5 195^ 19.1 6 1955 20.9 7 1956 19,3 8 1957 19.4 9 1958 20.1 10 1959 19.7 11 i960 20.9 12 1961 19.4 13 1962 19.9 14 1963 20.1 15 1964 19.4 16 1965 19.3 17 1966 19.-6 18 1967 18.9 19 1968 19.8 20 1969 18.6 21 1970 18.7 22 1971 18.7 23 1972 17.9 MEAN 19.7 7 relatively unreliable for monthly values for two reasons: 1. In the case of evaporation from a Class A pan in semiarid and arid areas exposed to sun, the water temperature is very high. Since the sur face depth is small, the pan evaporation is higher than the values which would occur for a lake or reservoir. 2. Because of a lack of data for pan temperatures, it is impossible to find the reduction coeffi cient of the pan evaporation. For these reasons no relation could be established between evaporation observed from the reservoir and from the pan, using the following relation: e - e reservoir Z (K) (2-la) e - e pan o z * E = C-E (2-lb) res pan where C is the pan coefficient for a given month, eQ is the average saturation vapor pressure at the temperature of the water surface for the given month, and e is the corresponding average vapor pressure at some specified height z above the water surface. Therefore another method was used, based on a combi nation of aerodynamic and thermal balances given by H.L. Penman and applied by Hassan. According to this method, at the Tripoli Airport station the annual quantity of TABLE 2-2 AVERAGE MONTHLY TEMPERATURE IN °G OVER A 23-YEAR SPAN (1950-1972) Average Monthly Tempera- Months ture in °G _______ I. Jan. 11.3 II. Feb. 13.0 III. March 15.0 IV. April 18.2 V. May 21,8 VI. June 26.0 VII. July 27.0 VIII. Aug. 27.8 IX. Sept. 25.1 X. Oct. 21.3 XI. Nov. 17.1 XII. Dec. 12.5 MEAN 19.7 TABLE 2-3 AVERAGE MAXIMUM TEMPERATURE IN °C OVER A l'7-YEAR SPAN (1950-1966) Average Monthly Maximum ________ Months____________Temperature in °C_____ I. Jan. 17.1 II. Feb. 19.3 III. March 21.8 IV. April 25.7 V. May 31.2 VI. June 3^.2 VII. July 35.8 VIII. Aug. 36.0 IX. Sept. 33.2 X. Oct. 28,k XI. Nov. 23.7 XII. Dec. 18.8 MEAN 27.1 9 TABLE 2-4 AVERAGE MINIMUM TEMPERATURE IN °C OVER A 17-YEAR SPAN (1950-1966) Average Monthly Minimum Months_____________Temperature in C I. Jan. 5-5 II. Feb. 6.2 III. March 8.1 IV. April 11.1 V. May 14.1 VI. June 18.5 VII. July 19.5 VIII. Aug. 20.2 IX. Sept. 18.9 X. Oct. 15.4 XI. Nov. 11.0 XII. Dec. 6.9 MEAN 12.9 10 evaporation is 2200 millimeters, ranging from 8 6 milli meters in December to 314 millimeters in July. In order to obtain the average annual and monthly evaporation (E) over many years, the following was established on the basis given by Hassan. There are two correlations,.one for the period from January to July: E = -0.025 t2' x '2.,4-llt 16.492 (2.2) ; and one for the period from August through December: , E = 0.It2 - 2.986t + 30 . 851 (2 . 3 ) where t is the average monthly temperature. As shown in Table 2-5, the monthly evaporation has been established for the period from 1944 to 197 2. Thus, the average yearly evaporation is 2206.9 millimeters. 1 This evaporation is high, and it is necessary to treat this problem. In some cases evaporation can be decreased by spreading non-evaporable materials on the surface of the reservoir; but due to the presence and duration of winds, the method is useless in this region. Another way of handling the problem is through a special kind of recharging of the reservoir water. From Tables 2-6 and 2-7, the average annual evapora tion is seen to be 7.1%, or 730,000,000 cubic meters per year from the reservoir surface, when the average yearly surface storage is approximately 10.5 million cubic meters. TABLE 2-5 MONTHLY TOTAL EVAPORATION IN MILLIMETERS YEAR I II III IV V VI VII VIII IX X XI XII TOTAL 19 62.6 79.3 109.8 202.9 244.5 289.6 524.0 275.2 214.9 149.1 89.5 91.5 2132.9 45 53.1 71.9 109.8 192.6 269.7 301.7 305.9 340.6 195.2 114.4 91.2 90.6 2136.7 46 60.7 84.8 135.5 224.3 261.1 302.7 297.3 289.2 212.6 164.3 107.4 87.9 2227.9 47 82.9 I63.2 207.3 188.1 244.5 286.2 315.2 528.0 233.7 147.5 89.9 92.5 2379.1 48 101.0 115.0 118.5 221.5 275.7 274.5 300.6 214.9 189.0 177.2 87.8 90.1 2165.8 49 75.6 82.0 115.0 I85.0 251.0 302.7 302.7 337.5 224.1 134.2 93.8 85.6 2190.3 1950 79.3 102.7 121.9 I89.6 263.6 304.9 259.1 233.7 142.9 142.9 88.7 93.6 2180.6 51 84.8 118.5 160.1 200.0 256.1 301.7 309.0 275.2 224.1 131.4 94.4 93.6 2248.9 52 108.0 71.9 169.6 198.5 243.2 319.2 323.I 275,2 292.1 169.7 89.7 89.3 2349.2 53 41.6 88.4 101.0 215.9 229.8 320.1 319.2 228.9 243.6 167.9 88.1 85.7 2129.9 54 56.9 79.3 164.8 191.1 224.3 314.2 283.9 201.6 205.9 112.3 97.6 89.O 2020.9 55 125-3 166.4 168.4 183.5 273.3 295.2 228.8 286.4 228.9 152.4 103.0 85.8 2387.4 56 120.2 79.3 125.3 111.6 235.2 295.2 319.2 224.1 219.5 116.6 89.1 91.0 2130.1 57 68.2 121.9 128.7 198.5 239.2 313.1 291.8 248.7 205.9 134.2 88.7 91.0 2130.1 58 60.7 113.3 155.2 I86.5 258.6 312.1 302.7 264.4 179.1 139.9 91.7 86.0 2150.3 59 84.8 86.6 161.7 195.6 252.3 294.0 289.6 275.2 269.7 212.2 88.1 90.1 2208.9 I960 86.6 153.6 168.0 I89.6 273.3 305.9 315.2 306.7 210.4 195.2 104.7 90.6 2399.8 i - 1 I S D Continued. on next page... TABLE 2-5, Continued YEAR I II III IV V VI VII VIII IX X XI XII TOTAL 1961 77.4 82.9 111.5 204.4 258.6 276.9 304.9 212.6 195.2 132.8 116.6 86.7 2060.6 62 104.5 92.0 163.2 211.6 259.9 280.4 317.2 193.1 212.6 1* 1* 1.*1 93.8 96. * ! 2168.2 63 108.0 109.8 120.2 194.1 208.7 303.8 323.1 283.6 226.5 112.3 99.8 88.1 2177.9 64 70.0 109.8 174.3 197.0 241.9 303.8 290.7 297.9 157.3 1* 16.0 90.8 88.3 2167.7 65 82.9 71.9 132.1 174.3 227.0 281.6 336.1 2* 18.7 22* 1.1 15* 1.0 93.3 86.0 2112.0 66 111.5 152.0 123.6 204.4 239.2 304.9 317.2 303.8 195.2 166.1 99.1 100.3 2307.2 67 68.2 IO9.8 188.1 200.0 258.6 280.4 291.8 217.2 137.0 99.8 99.8 97.*1 2212.6 68 70.0 135.5 158.4 227.0 283.9 188.5 309.0 303.8 22* 1.1 113. * ! 97.0 86.5 2297.1 69 90.2 128.7 177.4 192.6 278.1 300.6 29* 1.0 267.0 233.7 128.8 97.0 96.7 228*1.8 1970 135.5 U3.3 172.7 201.5 245.8 300.6 289.6 297.6 199.5 128.8 92.2 85.7 2262.9 71 92.2 88.4 150.4 222.9 266.1 300.6 303.8 2* 16.1 208.2 112.3 86.2 89-3 2173.*! 72 90.2 125.3 156.8 180.4 229.8 309.0 311.1 2* 18.7 — MEAN 84.8 106.8 146.2 199.4 251.5 298.8 307.5 268.9 217.0 1*19.9 9* 1.2 90.*1 2206.3 MAX 135.5 166.4 207.3 227.0 283.9 320.1 336.1 3* 10.6 292.1 195.2 116.6 100.3 2399.8 YEAR 1970 1955 1947 1968 1953 1965 19*15 1952 I960 I960 1961 1966 I960 MIN 41.6 71.9 101.0 174.3 208.7 274.5 283.9 193.1 157.3 112.3 86.2 85.6 2020.9 YEAR 1953 ^ 5,52,65 1963 1965 1963 1948 195*1 1962 196*1 195*1 1971 19*19 195*1 h- 1 00 TABLE 2-6 EVAPORATION DATA FOR 39 STORMS Volume of Water Evaporation in Date_________ in Cubic Meters____ Cubic Meters 10-15-54 40,000 3,600 10-29-54 50,000 4,500 11-11-54 800,000 60,000 12-15-54 4,377,000 218,850 2-8-55 3,420,000 246,240 4-3-55 10,000 480 4-14-55 70,000 3,360 4-39-55 8, 470,000 559,020 3-13,14-56 2,997,500 215,820 11-14-69 144,000 12,960 11-1-65 510,000 46,930 9-26-65 772,320 71,320 12-30,31-65 1, 290,000 92,880 2-5,6-66 332,500 29,930 3-2, 3-66 1, 441,370 103,780 4-3,4-66 332,400 30,400 4-21— 24-66 7,872,560 560,000 9-21-66 614,420 70,000 10-6-66 118,760 10,690 10-13-66 546,400 60,000 10-31-66 165,100 14,860 1,533,100 110,380 2-7— 9-67 1,140,800 85,800 3-20— 23-67 2,915,800 210,000 6-11,12— 67 1,775,550 165,120 9-23,24-69 8,665,000 580,000 10-29-70 2,390,000 157,000 1-29-71 250,000 12,000 continued on next page... TABLE 2-6, Continued Volume of Water Evaporation> in Date in Cubic Meters____ Cubic Meters 2-5,6-71 890,000 64,080 3-3-71 230,000 20,700 9-5-71 1,400,000 130,200 9-29-71 250,000 12,000 3-3-72 4,000,000 200,000 4-6-72 1, 500,000 140,000 4-13-72 250,000 12,000 4-2-72 300,000 14,000 4-28-72 1,150,000 106,950 5-10-72 3, 200,000 297,600 5-25-72 50,000 2,400 TOTAL 66,264,760 4,697,410 TABLE 2-7 YEARLY EVAPORATION IN PERCENT Flood in Thousands Evaporation in Percent of Cubic Meters_________ October-March April-September 0 -• 500 9.0 4.8 500 -■ 700 9.2 11.5 700 - • 3500 7.2 9.3 Over 3500 5.0 6.6 15 The only way to avoid this huge loss of water by « 1 evaporation is to put the stored water m the groundwater j reservoir during months of high evaporation. i C. Precipitation j 1 In order to show the area distribution of the average ; precipitation in the region, a map is reproduced giving • average isohyets from the Tunisian border to Horns (Figure , 2-4). Two areas of precipitation greater than 300 milli- ; meters per year can be clearly distinguished: the coastal . region east of Tripoli, and the area south of Gharyan. The Wadi Elmegenin is situated east of Gharyan. Since the period of observation in the wadi catchment area of 18 years is not enough for accurate analysis, data from nearby stations such as Azizia are used. Measurements at this station are available for the period from 194 7 to 1972; for the Gharyan station, from 1925 to 1972. The measurements of rainfall at these stations are the most reliable, and their positions represent the rainfall re gion in this area. Station Average Precipitation in millimeters Length tion of Observa- in years Aziza 210 46 Gharyan 312 42 Tarhuna 254 43 An arithmetic mean of the rainfall at Gharyan and 210+3120 Aziza could be used, ------^----- = 2 61 millimeters. Figur.ei 2-2 shows the isoh-yetal map of average precipitations in the wadi basin are of the order 26 3 millimeters. If the rainfall data at Suq-Gmatah, inside the wadi catchment ! i area, is considered at the same time as the nearest sta tion with respect to the Gharyan station, a definite con- i elusion can be made as to the precipitation relation at Gharyan and in the wadi basin. Assuming the recorded pre cipitation at Gharyan to be X, and at Suq Gmatah to be Y, we know that the average precipitation in Gharyan is 312 millimeters = X; and at Suq-Gmatah, 2 50 millimeters = Y. 250 312 = 0.8 Y = 0.8 X upper values Y = 0.5 X lower values Y = 0.6 5 X mean values Figure 2-5 shows daily precipitation of Gharyan plotted against the precipitation of Suq-Gmatah.- This graph shows the average precipitation of the catchment area to be 0.6 5 of the precipitation at Gharyan. Figure 2-6 shows the precipitation at Gharyan plot ted against the precipitation at the catchment basin, and also the average of precipitation of the two stations at Gharyan and Azizia. FIGURE 2-2 WADI ELMEGENIN ISOHYETAL MAP £RN]^ \ J 250,000 TJ H (D •H Legend: • Daily rainfalls ° Ten days' rainfall o* o* o ••• • 130 140 120 110 90 100 70 80 60 50 40 Gharyan Precipitation in Millimeters 30 H- h-1 03 1 The following relation was found: Y = 0.72X Y = average precipitation at the basin X = average precipitation at Gharyan Since the relation; between Gharyan station and Suq-Gmatah station was established to be 0.8, it can be concluded that Gharyan precipitation can be taken with a reduction factor between 0.72 5 and 0.8. Therefore, daily rainfall at Gharyan could be multiplied by 0.72 5, and taken as a good representation of the precipitation at the Wadi basin A double mass curve, shown in Figure 2-7, shows the relationship between the Gharyan and catchment stations. The plotted data for the sites together represent a single station. The change in slope is caused by change in the environment. Taking the intermediate points, the relation between the two stations can be defined by the line slope. Y = 0.65 X From this result and the previous one, we can consider that the precipitation in the catchment basin is 0.65 of that in the Gharyan station. 1. Precipitation-elevation relationships In analyzing the relation between precipitation and elevation, it is necessary to take into consideration other factors such as slope, wind direction, and climate. Figure 2-8 shows that precipitation generally increases FIGURE 2-7: Double Mass Curve of Precipitation -70 -65 CD & I -1 ( -1 O CO CD % w ■60 .5 -55 S' -50 .a -45 “35 -25 o • r H -20 )— I -10 Cumulative Precipitation at Gharyan in Hundreds of Millimeters 20 25 30 35 40 45 50 5: Station TABLE 2-8 DATA FOR DOUBLE MASS CURVE Year Catchment Area Precipitation in Millimeters Gharyan Precipitation in Millimeters Yearly Cumulative Yearly Cumulative 1967-1966 257.8 257.8 329.8 329.8 66-65 209.0 466.8 538.4 858.2 65-64 13^.7 601.5 333.7 1201.9 64-63 287.3 888.8 738.4 1940.3 63-62 266.9 1155.7 361.4 2301.7 62-61 435.4 1591.1 439.8 2741.7 61-60 120.6 1711.7 303.2 3044.9 1960-1959 235.8 1947.5 179.2 3224.1 59-58 170.1 2118.2 217.0 3441.1 58-57 163.5 2281.7 165.5 3606.6 57-56 418.0 2699.7 359.1 3965.7 56-55 138.2 2837.9 246.6 4212.3 55-54 262.6 3100.5 363.7 4576.0 54-53 145.4 3245.9 169.0 4745.0 53-52 229.0 3474.9 159.1 4945.1 52-51 198.0 3672.9 432.7 5333.8 51-50 353.^ 4026.3 215.6 5550.4 1950-1949 269.2 4295*5 522.7 6073.1 49-48 Unrecorded 3^5.5 6418.6 48-47 161.2 6579.8 47-46 124.7 6704.5 46-45 435.0 7139.5 45-44 374.0 7513.5 44-43 194.0 8267.3 43t42 175.7 8443.0 Continued on next jjage• • • 23 Table 2-8, Continued Catchment Area Gharyan Precipitation in Precipitation in Year Millimeters Millimeters Yearly Cumulative Yearly Cumulative 42-41 Unrecorded 114.6 8557.6 4i-4o 129.8 8687.4 1940-1939 360.1 9047.5 39-38 250.9 9290.4 38-37 223.3 9521.7 37-36 166.0 9687.7 36-35 282.0 9969.7 35-34 443,7 10413.4 34-33 551.4 10964.8 33-32 404.0 11368.8 32-31 248.4 II617.2 31-30 328.7 11945.9 1930-1929 464.7 12410.6 29-28 276.7 12687.3 28-27 244.9 12932.2 27-26 4295.5 912.1 13844.3 K = 0.85 calculated the excess P = g gross Pe' = runoff a = o -2 .62 ai = 0.174 b r o l i i 0.115 On the basis of the above data, P = -2.62 + 0.174P + 0.115 API (2-6) e g Runoff in millimeters, as shown in Table 2-11, shows the average annual runoff for Series .No. 1 and No. 8 to be nearly of the same order of magnitude, 18.00 millime- with elevation. The elevation basin map shows that the i highest point in the basin is 400 meters, and the lowest i I I is 2 20 meters. The mean values for yearly precipitation j at the two points are, respectively, 300 millimeters and \ 240 millimeters. This gives an average mean precipitation » I of 270 millimeters, which is very close to the mean found j by isohyetal map. j D. General Form of Regression Model Used to Simulate I Runoff j I pe = ao + ^iPg + a2API (2-4) : where a , a^, and a2 are the regression coefficients API = antecedent coefficient API = P 1 K 2 + P2K3 + P ^ K 1' 5 (2-5) ters. Runoff in millimeters for Series Nos. 9 to 12, in Table 2-12, shows the average annual runoff for Series No. j 9 to be nearly the same as for Series No. 1. This sug- j gests that the methods used in the study are compatible. j . . > phet 1 Calculation for the runoff coefficient c = p j gross j where P , is the runoff in millimeters and P is the ! net gross average precipitation in millimeters. The average pre- 1 cipitation depth in the catchment area was found to equal ! 26 3 millimeters per year. This is taken to calculate the , runoff coefficients for the average runoff obtained by a generation of series as shown in Table 2-10. According i to the analyses made in 1966, the following runoff coeffi- < 3 cient was obtained: Year Annual Mean Precipitation Runoff in in the Area in Millimeters Millimeters Runoff Coefficient (C) 1965-66 21.00 299.77 0.070 Average for 3 3 years 18.21 269.00 0. 068 As a result of the previous studies, the runoff coefficient can be taken as 0.07. Pnet C = pBHT = 0.07 gross Runoff coefficient = ^uno . . . . = 0.07 Precipitation 26“ Average annual runoff for the wadi basin according to Fig- g ure 2-9 is 10.500 x 10 millions of cubic meters. MEAN ANNUAL RUNOFF FOR NINE SERIES 1 2 3 4 5 6 7 8 9 18.47 33.4 17.34 17.92 22.44 23.0 25.9 17.82 18.24 Series No. 9 has the longest record period and has the same runoff value as series No. 1. It can be conclu- ded that series No. 9 is a good reference to use to cal- culate the runoff for 48 years of rainfall record. FIGURE 2-8: Precipitation-Elevation Relationship 300 g 200-h Elevation in meters 100 200 300 400 500 6Q0 28 _ l _______________________ I________________________ I________________________ 1________________________ 1________________________ I_________; ____________________________ -20 O t o < D •P a o •H u_ o M h o CO g •H r H i —I “ 10 .a a o p< I —I r d P . K) 0^ Percentage of Years 10 20 30 J 1 I 1 -----1 ----- 1 — 40 —L_ Mean Value ~ 10*500 million cubic meters o O O o o o o FIGURE 2-9: Duration Curve of Annual Runoff TABLE 2-9 DATA USED TO CALCULATE THE RUNOFF- COEFFICIENT FOR DIFFERENT SERIES Series No. Rainfall Stations Number of Years Period 1 Catchment Area 29 1944-73 2 Garyan 29 1944-73 3 Azizia 29 1944-73 4 Boargub 18 1955-73 5 Tarhuwa 29 1944-73 6 (Garyan + Azizia)/2 22 1951-73 7 (Garyan + Tumuono)/2 22 1951-73 8 (Garyan + Azizia)/2 + 9 observed years 48 1925-73 9 0.725 Garyan + Series No. 8 48 1925-73 10 0.725 Garyan + 9 observed years 48 1925-73 11 O.65 Garyan + 9 observed years 48 1925-73 12 0.80 Garyan + 9 observed years 48 1925-73 TABLE 2-10 RUNOFF COEFFICIENTS FOR DIFFERENT SERIES Number Average Runoff Runoff Series No. of Years in Millimeters Coefficient Remarks 1 29 18.47 0.0702 2 29 33.40 0.127 Over estimated 3 29 17-34 0.0659 4 18 17.92 .0.0681 5 21 22.44 0.0853 Over estimated 6 29 23.00 0.0875 Over estimated 7 22 25.93 0.0985 Over estimated 8 29 17.82 0.0678 9 48 18.24 0.0694 10 48 17.33 0.0659 11 48 14.49 0.0550 U nder- estimated 12 48 20.26 0.077 31 TABLE 2-11 ANNUAL RUNOFF IN MILLIMETERS SERIES NOS. 1 - 8? OJ K> T T , n Series No. Hydrologic No. Year 1 2 3 • 4 5 6 7 8 1 1944-45 25.08 29.24 11.27 17.31 17.31 2 1945-46 19.53 41.99 30.93 32.54 32.54 3 19 Aj.6-^7 1.15 1. 08' 18.02 6.36 6.36 4 1947-48 6.25 4.92 0.27 2.37 2.37 5 1948-49 13.89 26.28 28.28 24.46 24.46 6 1949.50 36.15 54.04 7.41 7.75 25.96 25.3^ 7 1950-51 11.74 17.19 21.25 23.25 19.70 18.35 14.93 18.35 8 1951-52 25.12 45.81 32.00 29.93 49.77 36.34 45.31 36.34 9 1952-53 9.82 7.68 4.77 9.07 10.98 4.88 5.36 4.88 10 1953-5^ 3.88 7.32 2.46 5-58 3.91 3.79 4.68 3.79 11 195^-55 29.91 38.23 15.50 12.20 32.26 24.57 27.09 29.91 12 1955-56 30.31 30.09 4.99 11.74 34.36 17.02 26.73 17.02 13 1956-57 28.05 42.11 14.75 36.37 47.10 29.19 46.77 29.19 14 1957-58 3.08 12.92 13.32 22.88 17.15 8.01 12.23 8.01 15 1958-59 7.60 14.2? 10.88 6.38 8.90 10.78 7-95 10.78 Continued on next page... TABLE 2-11, Continued Series No. No. nyaroiogic Year 1 2 3 4 . 5 6 7 . 8. . . 16 1959-60 8.32 6.31 2.76 6.82 6.06 3.43 6.14 3.43 17 1960-61 12.23 21.88 9.72 18.30 19.91 13.51 17.45 13.51 18 1961-62 32.60 61.42 26.31 29.94 19.16 39.38 38.55 39-38 19 1962-63 25.81 35.61 27.76 21.43 21.64 27.16 28.01 27.16 20 1963-611 75-16 107.90 65.60 46.16 42.52 85.32 74.47 36.00 21 1964.-65 19.45 32.70 4.81 7.90 15.80 19.45 23.88 19.45 22 1965-66 21.00 71.65 14.90 5.U 42.92 36.22 48.91 21.00 23 1966-67 15.15 23.83 12.18 21.80 17.80 16.34 14.73. 15.15 2k • 1967-68 15.72 36.96 18.05 12.83 24.83 23.01 15.72 25 1968-69 3-45 33.52 15-10 6.32 24.29 17-35 3.45 26 1969-70 15.54 34.35 14.11 28.91 22.16 27.81 15.54 27 1970-71 6.49 28.20 17.41 13.28 20.49 19-59 6.49 28 1971-72 20.90 67.14 25.28 40.78; 39.38 20.90 29 1972-73 12.42 34.02 30.96 32.49 12.42 TOTAL 535-80 989.66 502.93 322.61 471,28 666.99 570.43 516.85 MEAN 18.47 33.40 17.34 17.92 22.44 23.00 25.93 17.82 < x > < U 3 TABLE 2-12 ANNUAL RUNOFF IN MILLIMETERS SERIES NOS. .9/ - 12 No. nyU-LUJ-Ug-LC Year 9 10 11 12 1 1925-26 88,701 88.701 75.461 101,941 2 1926-27 13.687 13.687 10.364 16,187 3 1927-28 18.130 18.130 15.170 21.638 4 1928-29 28.158 28.158 22.502 32.967 5 1929-30 10.831 10.831 7.814 15.426 6 1930-31 5.500 5.500 3.579 7-914 7 1931-32 24.517 24.517 18.166 30.304 8 1932-33 39.237 39.237 29.196 46.922 9 1933-34 28.069 28.069 23.539 33.542 10 1934-35 8.106 8.106 5.765 10.572 11 1935-36 3.652 3.652 2.462 4.834 12 1936-37 6.124 6.124 3.864 8.406 13 1937-38 7.973 7.973 5.793 10.152 14 1938-39 20.202 20.202 16.487 23.963 15 1939-40 0.000 0.000 0.000 0.131 16 1940-41 3.232 3.232 2.628 3.839 17 1941-42 3.148 3.148 2.036 4.557 18 1942-43 2.729 2.729 2.107 3.751 19 1943-44 46.771 46.771 38.976 53.777 20 1944-^5 17.310 16.359 12.932 19.948 21 1945-46 32.540 21.947 17.239 27.675 22 I9k6-k7 6.360 0.000 0.000 0.000 23 1947-48 2.370 1.472 1.049 2.251 24 19^8-49 - 24.460 10.359 7.185 14.393 Continued, on next page• • • TABLE 2-12, Continued. No. Hydrologic Year 9 10 11 12 25 1949-50 25.940 28.980 22.013 34.823 26 1950-51 18.350 8.390 6.442 10.342 27 1951-52 36.340 26.965 21.742 31.756 28 1952-53 4.880 4.124 3.156 5.092 29 1953-5^ 3. 79O 3.529 2.893 4.165 30 195^-55 29.910 29.910 29.910 29.910 31 1955-56 17.020 16.073 13.326 18.890 32 1956-57 29.190 25.465 21.476 29.454 33 1957-58 8.010 5.592 4.201 7.052 34 1958-59 10.780 5.531 3-875 7.73^ 35 1959-60 3.430 2.667 2.120 3.234 36 1960-61 13.510 9.124 6.794 11.939 37 1961-62 39-380 35.407 29.577 44.428 38 1962-63 27.160 19.770 15.580 23.983 39 1963-64 36.000 71.226 61.508 81.085 40 1964-65 19.450 19.388 15.769 23.019 41 1965-66 21.000 21.000 21.000 21.000 42 1966-67 15.150 15.150 15.150 15.150 43 1967-68 15.720 15.720 15.720 15.720 44 1968-69 3.450 3.450 3.450 3.450 45 1969-70 15.540 15.540 15.5^0 15.540 46 1970-71 6.490 6.490 6.490 6.490 47 1971-72 20.900 20.900 20.900 20.900 48 1972-73 12.420 12.420 12.420 12.420 TOTAL 875.617 831.715 695.366 972.666 MEAN 18.242 17.327 14.487 20.264 TABLE 2-13 ANNUAL RUNOFF IN MILLIMETERS FOR SERIES NO. 8 Annual Runoff in Millions of F = — —— 100 Order No. (m) Year Cubic Meters (n+l) 1 19^4-45 22.810 3.3 2 1945-46 21.041 6.7 3 1946-47 20.844 10.0 4 1947-48 18.840 13.3 5 1948-49 17.317 16.7 6 1949-50 16.901 20.0 7 1950-51 15.726 23.3 8 1951-52 15.031 26.7 9 1952-53 14.162 30.0 10 1953-54 12.133 33.3 11 1954-55 12.100 36.7 12 1955-56 11.262 40.0 13 1956-57 10.625 43.3 14 1957-58 10.022 46.7 15 1958-59 9-855 50.0 16 1959-60 9.100 53.3 17 1960-61 9.00 56.7 18 1961-62 8.810 60.0 19 1962-63 7.822 63.3 20 1963-64 7.190 66.7 21 1964-65 6.242 70.0 22 1965-66 4.638 73.3 23 1966-67 3.760 7 6.7 24 1967-68 3.682 80.0 25 1968-69 2.826 83.3 Continued on next page... TABLE 2-13, Continued Annual Runoff in Millions of F — — —— 100 Order No. (m) Year Cubic Meters (n+l) 2 6 1969-70 2.19^ 86.7 27 1970-71 2.000 90.0 28 1971-72 1.986 93-3 29 1972-73 1.372 96.7 TOTAL 299.280 MEAN 10.320 III. GROUND WATER HYDROLOGY j | A. Occurrence Ground water occurs in voids or interstices of the earth material. The first types are found in unconsolida- j ted rock such as sandstone or conglomerate. These types ! of voids or pores are generally uniformly distributed and the permeability of these formations can be fairly well j determined by examination of a representative sample. j These types of formations usually have a large water quan- j i tity because their porosity is very high. Interstices of i the second type are found in massive rocks such as granite , j gneiss, basalt, and limestone. These are generally irregu larly distributed. The storage in an aquifer of these types of rocks is usually limited. The storage capacity of a formation is measured by its specific yield and is defined as the ratio of water | that will drain by gravity to the total volume of the satu rated material. Specific yield = porosity - specific retention (3-1) i B. Water Movement Water moves from the ground surface to the ground | water table in two ways: (1) infiltration, or (2) percola- j i 3 8 ' ' tion. 1. Infiltration This is the downward entry of water into soil. Infiltration capacity is the maximum rate at which a soil, in a given condition at a given time, can absorb water, a. Factors affecting infiltration rate Infiltration is a complex phenomenon and, be cause of the many variables involved, no general law for a computing rate has developed. Experience indicates that the infiltration rate of a given soil depends on its phy sical status and management history. Infiltration is of ten critically influenced by the composition of the soil surface, the number and size of pore spaces, the degree of compaction, and the presence and nature of vegetation. Thus a loose, coarse gravel will absorb water at much higher rates than a clay or loam soil. A soil surface * with undisturbed native vegetation or undisturbed soil structure shows higher rates than does the same soil with the vegetation removed and the surface plowed and harrowed. Typical infiltration rate curves not influenced by a higher water table, as found in test ponds in Kern County, California, are shown in Figure 3-1. The curve representing undisturbed soil indicates that after a short shutdown a repetition of itself occurs, but with a lower 39 FIGURE 3-1: Typical Infiltration Capacity Curve of Undisturbed Soil o CO o CD O C 0 O CM O CM Auq asd q . a a j ; ur uoTyruq-pTjui infiltration rate. On the basis of work done in the lab oratory with soil core by J.E. Christiansen ("Effect of Entrapped Air upon the Permeability of Soils"), the S- : t | shaped infiltration rate curve was explained as: - ! i (1) Initial decrease in permeability or filtration j ! rate is caused by dispersion and swelling of i the soil -particles and by air back pressure. (2) Increase in permeability is caused by the elim- | ( ination of entrapped air from the soil. j (3) Gradual decrease is due to biological activity in the soil. I The explanation of the S-shaped curve was sustained j later by permeability tests with sterile water and soil ; i by L.E. Allison, as in Figure 3-2. ! The permeability of sterile soil was maintained at i approximately the maximum rate, whereas the control opera ted under ordinary conditions followed the typical curve. Conclusions drawn from this experiment were that 1 sterile permeability tests conducted under prolonged sub- ; i mergence gave no evidence of soil aggregate breakdown due to purely physical causes. The reduced permeability appears to be due entirely to microbial sealing. The soil , pores probably become clogged with the products of growth, cells, slimes, or polysaccharides. If any of the observed t reduction in permeability was due in part to the disinte- ‘ 41 ' Sterile soil and water o CO o LO I —I •H o o CO o <N I —I o o co a - Infiltration in centimeters per hour CN \ — I FIGURE 3-2: Infiltration-Time Curves for Sandy Loam Soil Under Prolonged Submergence 42 gration of soil aggregates, the dispersion is believed to . . . I be due to biological causes; that is, the attack of micro- j i organisms on the organic materials which bind into aggre- 1 gates. j These products of microbial activity not only appear j to seal soil during wetting, but also tend to improve the aggregation of the soil upon drying. This aggregation may • in turn cause percolation rates higher than the initial J rates. In other words, if energy material is added to a | I soil so as to promote microbial activity, the percolation j rate could be expected to be higher than the initial run. j The other factor affecting the rate of infiltration j is the chemical composition of the water, particularly the i sodium percentage (ratio of sodium ion concentration to I the sum of sodium, calcium, magnesium, and potassium ions).; A high sodium water tends to deflocculate the colloidal i particles in a soil mass and thus hinder the movement of ; i water through it. Hard waters tend to infiltrate more rapidly than soft waters (less than thirty parts per mil- , lion of calcium and magnesium). Experiments show that surface applications of gypsum and calcium chloride have a beneficial, although temporary, effect upon infiltration, i rates, as shown in Figure 3-3, by increasing the hardness , of the applied water. The height of the ground water I • i table is also a very significant factor, if the water ! 43 : FIGURE 3-3: Effect of Gypsum and Calcium Chloride on Infiltration Rate Gypsum added, 4 tons per acre •H Hay June July August 2 Gypsum added, 4 tons per acre //////// •H r—I August 0 May June July Calcium Chloride added to maintain hardness of 200 ppm June July August table is near to ground surface. Spectacular increases in infiltration rates have been achieved by the addition of organic matter to the soil. The best results have been obtained with cotton- gin trash. The trash was applied in copious amounts, usually a 6-inch layer. Figure 3-4 illustrates the step- by-step development of infiltration rates following the application of cotton-gin trash in a field pond. Several steps identified in Figure 3-4 are described as follows: j Step 1: Cotton-gin trash applied to the soil and j i spaded. | Stp.n ? : . Water applied to pond and kept wet for 3 0 j days. This is called the "incubation" ‘ j period. j Pond dried until top few inches of soil , i nears wilting point. Residues of organic ; matter decomposition in proved soil aggre gation . Water reapplied, high infiltration rates obtained. Pond dried. Water reapplied. High infiltration rates tended to reach a sustained high rate, com- 1 pared with rate obtained on untreated pond.; Step 3: Step 4: Step 5: Step 6: Cotton gin trash add^d to Pond B, then kept nbist for 30 days to inyubat® ,Pond B (gin trash) f u CD _ L_ 210 _i________I _ 240 270 300 =r b. Vegetation trials Trials with vegetation were made for the purpose of increasing or maintaining infiltration rates. Several grasses and plants were tried, but the Bermuda grass ap peared to have the greatest possibilities for increasing the infiltration rates. It grew luxuriantly under pro longed wetting, provided the tops were not submerged, and it survived long periods of drought. c. Mechanical treatments ! | The treatments involved spading of the soil and . removal of top soil by raking or scraping the soil surface . j In general, any mechanical disturbance of a soil that con-! tains fine material will have a detrimental effect on the 1 infiltration rate, as shown in Figure 3-5. Reduction of the infiltration rate by surface soil disturbance is much more pronounced on soils containing fine material than on well-graded sands. Mechanical disturbance of the sands was found to be beneficial, even when they were nearly or completely saturated. d. Water surface depth ! i It was found that infiltration fluctuated in ! phases with the change in the depth of water or "head" during a spreading run. However, if a spreading run was j started and maintained at a shallow depth (0.2 - 0.3 foot); ! throughout a run, the infiltration rates tended to be j Infiltration Rate i n Feet per Day 1 Undisturbed Soil Water Off 140 120 100 80 60 40 20 Days 1 Disturbed Soil 0 20 60 80 40 Days - p 00 FIGURE 3-5: Effect o f Mechanical Disturbance o f Soil o n the Infiltration Rate higher and maintained themselves better than when the water was applied at a depth of 1 or 2 feet. This may have been caused by differences in sunlight affecting the soil temperature. These tests showed that certain plants will thrive with vthe shallow depths of water, whereas they j i i will not survive under greater depths. The effect of in- ! terruptions of spreading apparently depended largely on I the degree of drying that took place in the top soil. | f Short interruptions of up to several days caused only a , \ temporary detrimental effect on the infiltration rate. : After spreading was resumed for a few days, the rates re- ■ turned to what would have been expected had no interrup- 1 tion occurred. Air entering the soil during the short interruption was believed to be at least partly responsi ble for the decreased rate immediately following the in terruption. Interruptions of such duration that the top soil dried, resulted in an increase of infiltration rates over that 'which occurred at the time of the interruptions.. In some cases, such interruptions resulted in rate recov ery equal to the initial rate. Figure 3-6 represents a typical infiltration rate curve obtained many times on the various ponds as a result of prolonged interruptions. It should be brought to mind that the conclusions ; \ mentioned regarding the factors affecting the infiltration! rates are based largely upon experimental work in the fine-; 49: & >? a ) n f •p 0 ) 0 ) p ~ 3 a ) p§ 2 s •H Id 1 rH *H ^ o M Interruption in Spreading Sept. Oct. Nov. Dec. 0 ) I 8 •H | ,_______________ 3 ‘0 Aug. Interruption in Spreading r H Dec. Nov. Sept. Oct. EIGURE 3—6: Effect of Interruptions in Spreading on Infiltration Rates. (A) Where free water disappears from surface but soil remains wet. (B) Where top 6 inches of soil dries to or approaches wilting point. textured sand loams of the San Joaquin Valley.. It should also to noted that the influence of the various factors previously discussed are generally limited to the upper most foot of soil. 2« Percolation vertically downward under the influence of gravity. How ever, until the water content of the soil reaches its spe cific retention, water will be held by molecular attraction in the form of thin films coating the individual soil par ticles. Water in excess of retention capacity will slowly percolate until the zone of saturation is reached. Percolation is laminar gravity flow; thus, from the Darcy equation for laminar flow through porous materials: where Q = the discharge in gallons per day A = the cross-sectional area of the saturated material p = the effective porosity and is usually as sumed to be equal to the specific yield After entry into the soil, water tends to move V (feet per day) Discharge in cubic feet per day Effective pore hole area in square feet (3-1) Q = 7.48 VpeA (3-2 51 V (™) J- where 'S. = I, which is the hydraulic gradient of the flow Q = (Ld£ kp (f)A (3-3) fj. e Li - the dynamic viscosity of water which varies in versely with the temperature. The term 7 i+8 ( ■* )kp is the permeability coefficient, P. H" S 7 M- 8 p = kpe gallons per day per square foot (3-4) i _ 86 ,400 cod2 - — — - ------------------------------- , 2 6 d Pe P = (1.26 x 10 ) < ---- (3-5) M From the above equation we see that P is a function of the pore size and the effective porosity. The U.S. Geo logical Survey defines the "standard coefficient of perme ability" as the rate of flow in gallons per day of water, at a temperature of 6 0°F, through one square foot of the cross-section of the aquifer, under a hydraulic gradient of 100%. The "field coefficient of permeability" is the rate of flow in gallons per day through a cross-section one foot thick and one mile wide, under a hydraulic gradient of one foot per mile. Theim computed the field permeability by locating two observation wells within the cone depression of a pumped well. He measured the distance between the well and the observation wells, the thickness of the aqui fer, the discharge of the pumped well, and the drawdown in the observation wells after the pumped well had been carried. 52 P was found as follows: P = 5 2.7 Q log rq m(s2-s 1T~* rv^ P = 527.7 Q log *i m (:s2-s1) r 2 where m = the thickness of the aquifer s2 — s = the difference in the drawdown in the two observation wells r^ and r2 = the distances from the center of the pumped well to the two observation wells The quantity Pm = coefficient of transmissibility which is the ability of the aquifer to transmit water in..gallons per day per foot. C. Source of Ground Water in the Wadi Elmegenin Area The ultimate source of the ground water in the wadi area is rainfall. Replenishment to the ground water body is by infiltration from rain, seasonal runoff, and irriga tion water applied in excess of plant requirements; and from underflow through existing faults. Infiltration of rain is a significant source of re charge to the ground water when the soil moisture is not deficient. The annual rainfall is 26 3 millimeters on the average. Infiltration from streams flowing across the wadi is an important source of recharge of the ground water. Measurement of flow at many profiles along the stream shows 53 (3-6) (3-7) that the channel infiltration is very great. Figure 3-7 shows the infiltration rate for different wadi profiles. Infiltration from irrigation water applied to cultivated lands contributes heavily to the ground water supply; this contribution is more than that from the wadi runoff. D. Ground Water Movement in the Wadi Elmegenin Area Ground water moves in response to the hydraulic gradi ent, according to Darcy law Q = PIA, from the area of re charge to the area of discharge. Under natural conditions, the unconfined water in the valley area moves along the side of the valley towards the north where there is heavy pumpage. Water level contours show that the movement of water in the unconfined aquifer is generally in the direc tion of the land slope (see Figure 3-8). The gradient of the water table is governed by the rate of flow, the thick ness , and permeability of the materials through which water moves. Irregularities in the shape and slope of the water table may be caused by gain or loss in the ground water reservoir, thickness and permeability of material, and irregularities in the shape of the bedrock floor. E. Water Depth in the Wadi Area The depth to the unconfined ground water in the area is generally related to the configuration of the land s.ur- 54 FIGURE 3-7; Infiltration Rate at Different Wadi Profiles 1300 jg 1100 E s 1000 o •H 900 3 - 300 Morabito Bridge and Ben Ghishir Bridge Morabito Bridge and Bab-Azizia Bridge Sidi-Gelani Weir and Amoit Weir Main Reservoir and Amoit Weir Flow in Cubic Meters per Second 10 20 30 40 50 60 70 80 J_____ I ______I ______I _____ t ____I _______L 55 90 100 110 120 130 140 face; generally, the depth is greater where the land sur face is high. The depth to water, which ranges from 40 to 80 meters, is shown in Figure 3-8. F. Fluctuations in the Wadi Area During years of low precipitation and surface runoff, pumping of ground water from wells is generally increased and the water table declines. Conversely, during periods of high precipitation and abundant recharge to the ground water reservoir, withdrawal of ground water by pumping is reduced and the water table rises. G. Ground Water Use in the Wadi Area Ground water is the chief source of all water uses in the area because of its ready availability and conven ience. The annual pumping in the area was estimated at 20 million cubic meters per year. 56 IV. ARTIFICIAL STORAGE OF GROUND WATER A. Direct Benefits of Artificial Recharge The basic benefits of artificial recharge of ground water can be listed under the following categories: (1) Relief of overdraft. The average general rate of water decline in the Ben Ghishir area was 0.4 - 0.5 meters per year during the period 1966-1967, and to 2.0 meters per year during 1972. This sudden decline in the water table prompted a substitution of artificial recharge to change that condition. (2) Prevent dewatering of all parts of the ground water reservoir. (3) Increase conservation of local runoff. (4) Store water to reduce cost of pumping. (5) Reduce or prevent salt-water intrusion. (6) Use of ground water reservoir as a storage and distribution system. This can be done by planned extractions of ground water during peri ods of low precipitation, while subsequent re plenishment can be made during periods of high precipitation. 57 B. Selection of Recharge Sites Selection of recharge sites must be based on an eval uation of surface material for maximum percolation rates and physical characteristics of underlying material for the most efficient utilization of storage capacity and transmissibility of the aquifer. The texture of surface soils determines initial and sustained percolation rates. Geologic and hydrologic conditions that are deter mining factors in the rates of percolation, storage capa city, and transmission below the soil surface are: (1) Permeability of aquifer and effect on trans mission rates of ground water to areas of heavy pumage. (2) Specific yield and thickness of sediments rela ted to potential storage capacity. (3) Structural and lithologic barriers as impedi ments to ground water movement. (4) Water table levels as affecting percolation rates and storage capacity. (5) Pattern of pumping draft. (6) Water quality considerations. (7) Operation and maintenance problems. 1. Soil Surface Soil types are important factors in the estab- 58 lishment of initial infiltration rates. In general, soil must have a coarse texture to have higher initial and sustained infiltration rates. Soil surveys are usually limited to the top six feet of soil. Before the final selection of a site is made, deep holes should be dug for detailed investigation to determine if impermeable or relatively impermeable layers exist. 2. Natural ground slope The natural ground slope is somewhat related to the surface soil, and is a good guide for obtaining an estimate of long-term infiltration rates. 3. Water quality There are two basic types of problems which deal with the character .of the water for recharge purposes: (1) those which affect infiltration rate, and (2) those which endanger the public water supply. The quantity of silt in the water has a decisive influence on the infil tration rate. The allowable concentration of silt at each project is usually determined by experience, and is usu ally less than 1000 ppm. The public water supplies may become polluted as a result of the movement of bacteria with underground water. This hazard exists when polluted water is injected into the underground aquifer; a lesser hazard exists in the case of surface spreading methods. 59 4. Pattern of overdraft The decline of the water table in many cases dictates the recharge sites. The only way to alleviate this depression is the addition of water to the ground water by artificial recharge. C. Methods of Recharge Artificial replenishment of ground water is accom plished primarily through works designed to maintain or increase infiltration and percolation rates and to increase the surface of wetted area. Although no two projects are identical, most of them utilize variations or combinations of the basic ideas described below. (1) Maintaining continuous flow in stream channels This method is particularly applicable to arid re gions where the flow is not perennial. Flow may be main tained by releases from a reservoir sufficient to supply flow equal to the absorption capacity of the stream bed. The utilization of stream beds represents an efficient and economical way of artificial recharge. Further improve ment may be made by plowing the stream bed to increase the wetted area. Check dams have been used to retard the flood flow, partially desilt the water, and maintain small reservoirs back of the dam. (2) The furrow and ditch method In the furrow method the water is transported through 60 a series of furrows or ditches, somewhat like an irriga tion system. This method is successfully applied to rough, stony terrain, and to areas where slopes are too steep. The ditches and furrows are shallow, flat-bottomed, and close together to create the greatest possible infiltra tion area. In general, three types of ditches and furrows are commonly used: (1) Contour type--where the ditch follows the ground contour. (2) Lateral type--at right angles to the main canal. Open cuts through the bank of the main feeder canal provide entrance to the laterals. Gates are placed at each entrance to control the quan tity of water entering each furrow. (3) Tree-shapes— where the water is diverted from the main canal to successively smaller canals and ditches. For each series of ditches and furrows, it is neces sary to place a collecting ditch at the lower portion of the spreading area to collect and divert the excess water into the main canal. This type is usually used where the land value is relatively inexpensive, since the wetted area is about 10 percent of the gross area. 61 (5) Basin method This method impounds water in a series of small basins formed by dikes and arranged to permit planned sub mergence of the entire area. The overt,opping of the basin consists of binding massive material, such as rock, to gether with heavy hog wire to form a dike. The basins are usually arranged in a series by using the full advan tage of surface contours, so that the overflow from the upper basin will flow into the next lower basin by gravity. The basin method may be used where the ground surface is irregular and spotted with shallow gullies having rid ges. It has the advantage of furnishing the maximum wet ted area. Only the top of the dikes are exposed and used for surface roadways. The use of recharge basins is especially suitable wherever an aquifer lies above an impervious stratum and contains ground water with a free surface. Aquifers are frequently alluvial deposits or the outcrop of pervious bedrock, such as creviced limestone, sandstone, or con glomerates. As the recharge proceeds, the static eleva tion of ground water in the vicinity of the recharge basin rises and forms a ground water mound. This may become continuous with the recharge water in the basin. When the ground water mound occurs, a hydraulic gradient is estab lished between the water level in the spreading basin and 62 the ground water static level. This gradient produces a radial flow of water as the mound expands its circum ference. This condition was termed "pressure flow," since the water was under pressure as evidenced by lateral movement. It has been found that greater flexibility in opera tion and maintenance can be achieved by using a minimum of two basins, so that the first basin can be utilized as a sedimentation pond to remove silt. This also permits the project to remain in operation during periods when spread ing must be discontinued and the basins dried for cleaning to re-establish a new infiltration rate. (4) Flooding method The flooding method involves diversion of water to form thin sheets which flow over relatively flat land. Highest infiltration rates are obtained in areas having gentle slopes. This method is cheaper than any other and provides a higher rate of infiltration. One disadvantage is that the water is not as easily controlled as in other methods. To avoid damage at the upstream end of the area to be flooded and to return water to the stream canal, suitable embankments are used. (5) Trench recharge method This method works well when the shallow subsurface strata restricts the drawdown percolation of surface water, 63, as illustrated in Figure 4-1. If the barrier measures up to a thickness of more than 25 feet, this method becomes very expensive and difficult. In the trench recharge method, the impermeable mater ial can be removed by excavation and the trench back filled with gravel which would remove a large part of sedi ments carried by water; the backfill in the trenches could be scraped out and cleaned periodically. To estimate the recharge volume per unit length of a trench at any given time: /9 h h 2\ q = 2X S (4 h - h + (,-£) )= 2MSX o 13 w o 3 h / o \ w / S = specific yield of the aquifer /o h h 2\ M = (I h - h + -2- (r-^) ) 13 w o 3 h / \ w / h ■= thickness of groundwater aquifer h^ = thickness of permeable material above ground water table The recharge volume is also given by: Q = H qdt J o q = infiltration rate per unit length of trench for a given time (6) Recharging through wells The use of injection wells is confined to an area where thick impermeable layers or space limitations pre- 64 vent the application of any other method. The injected water flows away from the well in the form of a wave which spreads radially; the rate of flow through this wave varies from the rate of injection at the well to zero at the front of the wave. Wells that are gravel packed are more efficient than those without gravel envelopes. When water is injected under pressure a special concrete seal should be placed around the top of the input aquifer to prevent upward movement of water along the outside edge of the casing. The maximum spacing of recharge wells is determined by the ratio of injection rate and rate of original ground water flow per unit length of barrier. The recharge rate is a function of the permeability, hydraulic gradient, length of casing penetrating the aqui fer, and the number of casing perforations.. Chemical in crustation can be reduced by placing the perforations, below the water level at all times. In general, recharge water should be clean, have no high sodium content, and should be chlorinated to maintain an adequate recharge rate. The water should not fall freely in the well, to avoid aeration. Location of recharging wells and pumping wells should be roughly parallel to the natural contours, recharging wells being upstream from pumping wells. 65 D. Hydraulic Analysis 1. Free aquifer Recharge rate Q is equal to: frP(h 2 - K 2) = 2.3 log ( r / r ) C+-2a) ' o w Symbols are identified in Figure 4-2a for a recharge well penetrating a free aquifer, and in 4-2b for a con fined aquifer. 2. Confined aquifer Recharge rate Q is:equal to: 2 tt P (h - h ) p i _ W ___________ O / ■ p \ r 2.3 log (r /r ) & o w 66 G c ru tftL -fd fe j french W 0 !rtgtriaj. U/cdef ///// //S '//;/'////, /y //S/////////// v>7//// / / / / / / S ' ////// '////, FIGURE 4-1: Aquifer Recharged through Trench-Probolic Wetting Front w " ■> s s y s / y s - p ’ s - jr ? 7 ■ tf- 777777777 < J ) 00 FIGURE 4-2: Radial Flow from Recharge Wells Penetrating ( a . ) Free and (b) Confined Aquifers i V. YEARLY SURFACE WATER BALANCE IN THE WADI-ELEME'GENIN RESERVOIR The reservoir capacity curve is shown in Figure 5-1. To analyze the condition of utilization of this water, we must know all loss components, mainly evaporation and infiltration losses in the reservoir basin. As mentioned in Chapter I, the calculated loss due to evaporation was found to be approximately 7 percent. The losses due to infiltration in the reservoir basin can be calculated according to the hydrologic equation: Inflow = Outflow - Losses (5-1) Table 5-1 shows the annual runoff and losses. This table shows that 2 6 percent of the inflow will infiltrate into the reservoir basin, and therefore: Total losses = Evaporation + Infiltration = 7 + 26 = 33% The remaining 67% will be distributed for two purposes: (1) irrigation scheme, and (2) recharging project. 69 TABLE 5-1 ANNUAL RUNOFF AND LOSSES IN CUBIC METERS INFLOW OUTFLOW LOSSES Hydrologic Year Runoff in Cubic Meters Outflow in Cubic Meters Evaporation in Cubic Meters Infiltration in Cubic Meters 195^-55- 17,317,000 11, 900,830 1,095,200 4,320,970 1965-66 12,133,295 8,383 ,465 848,810 2,401,000 1966-67 8,809,930 5,537,240 727,390 2,545,300 I97O-71 3, 760,000 2,788,220 253,780 1,038,500 AVERAGE 10, 500,000 7,070,000 730,000 2, 700,000 PERCENT 100 67 7 26 70 FIGURE 5-1; Reservoir Capacity Curve 283 Spillway Crest -280 •H -270 260 Volume of Water in Millions of Cubic Meters 0 10 20 30 40 50 »_ _ _ _ _ !_ _ _ _ _ _ I_ _ _ _ _ _ I_ _ _ _ _ _ I_ _ _ _ _ _ I_ _ _ _ _ _ !_ _ _ _ _ I_ _ _ _ _ _ I_ _ _ _ _ _ I_ _ _ _ _ _ L VI. IRRIGATION PROJECT A. Soil Study at the Downstream End of the Reservoir Soil studies for the three proposed areas at the downstream end of the reservoir (shown in Figure 6-1) have been carried out in detail. (1) Area No. 1: Al-Khitnah Area This area is situated 7 kilometers north of the res ervoir. The land Is mainly flat, and is characterized by a mild longitudinal slope towards the north. The highest point is about 250 meters above sea level, while the low est point is at an elevation of 215 meters. 1. Soil texture Table 6-1 shows the soil classification for this area to be sand and deep clayey sand. 2. Soil classification a. Deep soil This type of soil is clayey sand and is found at depths between 8 0 and 12 0 centimeters; deeper in some places. It can be classified as: (1) Reddish-brown, deep clayey sand on marly limestone. Covers an area of 242.5 acres. 72 Physical prQperties--Table 6-2 shows the main components of this soil to be fine sand (80 to 85%) and clay (15 to 2 0%). It has an average porosity ranging from 39 to 41% with a specific retention of 26 to 30%, and an infiltration rate of 3.40 millimeters per minute, as shown in Figure 6-2. Chemical properties— Table 6-3 shows that this soil has a CaCOg content of 10 to 19% throughout its en tire depth. The N and P2O5 contents are small, but the soil is rich in K^O. Agricultural value--Clayey sand represents the best type of soil in this area. (2) Reddish-yellow, deep sand on marly lime stone, occupying an area of 560 acres. Physical properties— Fine sand content ranges from 87 to 93%, and clay .from 6 to 8% with a specific re tention of 21 to 2 4%. The infiltration rate is 1.9 milli meters per hour (see Figure 6-2). Chemical properties— The CaCOg content in this type of soil is 7 to 13%, with an alkaline reaction. The N and P2O5 contents are very small, while KgO content is average. Agricultural value--This soil is of lesser quali ty than the clayey sand. (3) Reddish-yellow, deep sand with accumulation 73 of limestone on a marly limestone sub stratum. Covers an area of 225 acres. Physica1 properties--Fine sand content from 86 to 92%, and clay from 9 to 11%. Specific retention is 21 to 22% with a permeability coefficient (k) = 1.5 to - 3 2.7 x 10 centimeters per second. Chemical properties--The soil contains a medium value of CaCOg and is constant along with whole depth with a medium alkaline reaction. Agricultural value--This sand has a lower agri cultural potential than the first two types because of the limestone stratum, which hinders root growth. b. Medium deep sands These are usually clayey sands found at an average depth from 5 0 to 7 0 centimeters. They can be classified as follows: (1) Reddishr-brown, clayey sand. This covers a very small area, and its physical and chemical properties are identical to No. 1 in the deep sand group. (2) Reddish-yellow sand. This covers an area of 277.5 acres. Physical and chemical properties are the same as Mo. 2 under deep sand. 74 SOIL TABLE 6-1 TEXTURE OF AL-KHITNAH AREA Depth, Centimeters Sand Description (percent) Total Hygroscopic Water Profile Coarse Fine Silt Clay Sand Clay Classification I 0-20 2.9 87.1 1.9 8.9 90.0 10.0 1.15 Sand 20-40 3.9 86.9 1.3 7.9 90.8 9.2 1.00 t ! 40-60 3.8 86.3 2.7 7.2 90.1 9.9 0.93 70-85 2.1 88.7 1.1 8.1 90.8 9.2 0.93 I I 100-120 1.5 87.6 2.5 8.4 89.1 10.9 1.18 I I 120-150 0.8 87.5 3.1 8.6 88.3 11.7 1.22 I I II 0-20 0.6 92.6 1.2 5.6 93.2 6.8 O.96 Sand 30-50 0.1 89.2 1.9 8.8 89.2 10.7 1.24 1 1 50-80 0.1 88.1 2.8 9.0 88.2 11.8 2.13 1 1 100-130 0.1 88.1 3.4 8.4 88.2 11.8 1.29 1 1 150-180 0.1 87.1 2.3 10.5 87.2 12.8 1.61 Clayey Sand III 0-20 0.1 86.3 5.5 8.1 86.4 13.6 1.23 Sand 30-50 0.1 90.3 3.8 5.8 90.4 9.6 1.03 1 1 70-90 0.1 85.1 6.0 8.8 83.2 14.8 1.56 1 1 100-120 0.1 93.^ 1.2 5.3 93.5 6.5 1.01 1 1 170-190 0.1 83.0 5-6 11.3 83.1 16.9 1.48 Clayey Sand : IV 0-20 0.1 84.3 3.8 11.8 84.4 15.6 1.55 Clayey Sand ■ £0-40 0.1 84.8 4.2 10.9 84.9 15.1 1.60 " -J Cn 50-70 0.2 85.6 3.2 11.0 85.8 14.2 1.71 1 1 1 1 TABLE 6-2 SOIL PHYSICAL PROPERTIES OF AL-;KHITNAH AREA Profile Depth, C entimeters Hygro scopic Water Wilting Point, Percent Density, Grams per Cubic C entimeter Specific■ — Gravity Porosity, Percent Field Capa city, Percent Permeability Coefficient, C entimeters per Second I 0-20 0.96 5.2 1-55 2.65 41.5 24.2 1, 5.x 10"3 30-50 1.24 4.11 1.54 2.66 42.1 22.1 2.7 x 10";? 60-80 2.13 6.27 1.60 2.64 39.39 23.6 4.6 x 10"' 100-130 1.29 4.5 1.58 2.65 40.38 21.5 5.3 x 15“^ 150-180 1.61 6.9 1.56 2.65 41.13 26.2 2.7 x 10"J II 0-20 1.20 4.43 1.60 2.62 38.93 24.15 1.56 x 15~3 20-40 1.13 3.94 1.62 2.6l 37-93 21.12 2.3 x 10 ^ 40-60 1.06 3-98 1.61 2.65 39.24 23.32 1.89 x 15J 80-100 1.17 4.09 1.60 2.63 39.16 22.50 2.2 x 10"' 130-150 1.41 6.54 1.56 2.58 39.53 26.19 3.3 x 10"^ III 0-20 1.25 4.83 1.61 2.64 39.01 23.22 1.43 X 10-3 30-50 1.03 3.87 1.60 2.60 38.45 22.2 1.13 x 10 \ 70-90 1.56 5.84 1.62 2.62 38.17 23.91 8.23 x 10 3 100-120 1.01 3.53 1.60 2.63 39.16 21.20 1.43 x 15-3 IV 0-20 1.55 4.52 1.56 2.62 40.45 27.15 20-40 1.60 5.15 1.57 2.61 39.64 27.95 56-70 1.71 6.23 1-55 2.65 41.50 28.22 i -4 ' CD SOIL TABLE 6-3 CHEMICAL PROPERTIES OF AL-KHITNAH AREA Profile Depth, Centimeters CaCO 3» Percent pH E.C. mhos per q , Centimeter ^ a , OJ.on Percent at 25 C Salt, Percent Humus, N, Percent Percent p2°5> Milli grams k2o, Percent H2° KC1 I 0-20 8.82 8.6 7.4 0.56 43.1 0.01 0.61 0.03 <1 22.2 20-40 7.77 8.4 7.4 0.52 40.0 0.01 0.48 0.02 <1 20.2 40-60 7.77 8.4 7.3 0.61 38.4 0.01 0.50 70-8 5 13.65 8.4 7.4 0.63 73.0 0.01 0.57 100-120 10.29 8.4 7.4 0.98 44.1 0.02 0.48 120-150 9.66 8.5 7.4 1.20 44.5 0.03 0.41 II 0-20 5.46 8.6 7.5 O.63 39.1 0.01 O.63 0.03 <1 23.0 30-50 7.98 8.6 7.6 0.58 44.7 0.01 0.44 0.02 <1 21.0 60-80 10.50 8.4 7.4 O.69 45.1 0.02 0.43 100-130 10.92 8.6 7.6 1.23 43.7 0.03 0.43 150-180 9.03 8.6 7.6 1.31 45.3 0.03 0.40 III 0-20 11.2 8.2 7.2 0.47 30.9 0.00 1.04 0.05 <1 24.0 30-50 10.78 8.2 7.2 0.40 33.7 0.00 0.75 0.04 <1 19.4 70-90 13.53 8.2 7.2 O.69 38.8 0.01 0.64 100-120 6.55 8.6 7.4 0.51 32.7 0.01 0.55 170-190 12.89 8.6 7.4 0.69 41.0 0.01 0.63 IV 0-20 15-74 8.3 7.2 0.55 44.9 0.01 0.53 0.01 <1 24.5 20-40 14.27 8.4 7.3 0.49 42.7 0.01 0.39 0.03 <1 22.1 : 50-70 17.32 8.3 7.2 0.61 43.7 0.01 0.43 -J -J f-Capacity in Millimeters per Minute 3 hrs 2 hrs 1 hr 0 hrs Time in Minutes i "J CO I FIGURE 6-2: Standard f-Capacity Curves at Al-Khitnah Area c,. Shallow sand This is classified as: (1) Reddish-yellow sand. Covers an area of 245 acres with an average depth of 25 to 30 centimeters. d. Sand dunes Sand dunes cover a total area of 9 5 acres in the eastern and some parts of the cen tral section. These are deposited in the form of relatively high dunes, from 1 to 2 meters. These places are unsuitable for agricultural production. (2) Area No. 2: Hosh Area This area is situated 10 kilometers north of the reservoir. 1. Soil texture Table 6-4 shows the soil classification to be clayey sand and sand. The pedological covering of the region is comprised of: a. Deep soil (1) Reddish-yellow, clayey carbonate sand. Covers an area of 302.25 acreas, or 10.43% of the total land area. This soil has a 79 good infiltration rate of 230 millimeters per minute, as shown in Figure 6-3. Pro duction value of this soil is highest in this zone. (2) Reddish-yellow sand. Total area of this type is 535 acres, or about 18.45% of the total area. Physical properties--The soil is exposed to fre quent drifts of wind. The porosity is 40% with an average infiltration rate of 2.5 5 millimeters per minute. Chemical properties--CaCOg is present along the entire depth of the soil profile. This soil has poor humus, and is also poor in nitrogen and phosphorus; it has a moderate potassium content. b. Medium-deep, reddish-yellow sand on sandy clay carbonate. This soil covers an area of 1198.0 acres., or 41.32% of the total area. Its porosity is about 39% with an average infiltration rate of 2.55 milli meters per minute. Chemical properties--CaCOg appears along the entire depth of the soil profile at 8.2%, with a weak alkaline reaction. E.C. value is within 0.5 8 to 11.0 2 at 25%. Total salt content is from 0.011 to 0.26%. 80 TABLE 6-4 SOIL TEXTURE OF HOSH AREA Description (percent) Sand Total Depth, ; - ; ------------- Hygroscopic Profile Centimeters Coarse Fine Silt Clay Sand Clay Water Classification I 0-20 3.0 82.3 4.9 20-40 0.1 81.5 6.5 50-70 0.1 88.1 3.0 90-110 0.2 84.9 4.9 150-170 0.1 93.0 1.3 II 0-20 0.1 89.6 2.8 40-60 0.1 80.8 7.5 80-100 0.1 82.5 6.6 120-140 0.1 90.3 3.0 160-180 0.2 81.8 6.8 III 0-17 1.1 94.4 0.4 17-32 0.1 96.4 0.6 32-48 0.1 92.3 1.8 50-70 0.2 73.7 7.1 70-90 0.2 70.8 8.1 120-140 0.1 90.1 2.1 9.8 85.3 14.7 Clayey Sand 11.9 81.6 18.4 i t n 8:8 88.2 11.8 i t 1 1 10.0 85.1 14.9 i t t i 5.6 93.1 6.9 Sand 7.5 89.7 10.3 Sand 11.6 80.9 19.2 Clayey Sand 10.8 82.6 17.4 Clayey Sand 6.6 90.4 9.6 Sand 11.2 82.0 18.0 Clayey Sand 4.1 95.5 4.5 Sand 2.9 9 6.5 3.5 1 1 5.8 92.4 7.6 1 1 19.0 73.9 26.1 1 1 20.9 71.0 29.0 7.7 90.2 9.8 i t < 3 0 i —1 TABLE 6-5 SOIL PHYSICAL PROPERTIES OF HOSH AREA Profile Depth, Centimeters Hygro- scopi c Water Wilting Point, Percent Density, Grams per Cubic Centimeter Specific ,.;Gravity Porosity, Percent Field Capa city, Percent Permeability Coefficient, Centimeters per Second. I 0-20 1.49 5.13 1.56 2.65 41.13 26.25 9 X lot 20-40 2,00 4.99 1.58 2.76 40.22 28.01 9 X 157 50-70 1.47 5.43 1.55 2.66 41.17 27.13 9 x 15"^ . 90-110 1.61 5.34 1.56 2.64 40.90 25.84 3.4 x 10_% 150-170 1.06 4.88 1.63 2.64 38.20 24.71 6.78 x 10 II 0-20 1.16 5.12 1.63 2.64 38.26 23.82 5 x 15~3 , 40-60 1.78 8.35 1.51 2.60 42.12 28.45 6.5 x 10 i 80-100 1.62 9.12 1.50 2.62 42.75 49.81 8.9 x loy 120-140 1.23 5.25 1.65 2.66 37.96 24.05 3.5 x 10% 160-180 1.20 6.25 1.59 2.62 39.31 25.48 1.9 x 10”- ’ III 0-17 0.80 5.25 1.65 2.64 37.50 24.32 9.1 x 10~3 17-32 0.61 4.89 1.63 2.6k 38.25 25.16 1.25 x 10"^ 32-48 1.02 5.12 1.62 2.62 38.40 25-38 1.25 x 10,“J 50-70 1.46 6.32 1.56 2.65 41.13 28.13 3.4 x IOjJ 70-90 1.52 6.17 1.55 2.6 k 41.28 28.44 1.6 x 10% 120-140 1.28 5.43 1.63 2.6 k 38.25 25.02 1.8 x lO'-3 00 K> TABLE 6-6 SOIL CHEMICAL PROPERTIES OF HOSH AREA Profile Depth, Centimeters CaCO^ Percent pH E.C. mhos per Centimeter at 25°C Sat., Percent Salt, Percent Humus, Percent N, Percent P205’ Hllli- grams k2°, Percent H2° KC1 I 0-20 10.76 8.2 7.0 0.5? 30.4 0.01 0.44 0.02 1.0 15-6 20-40 10.34 8.2 7.0 0.47 32.3 0.01 0.44 0.02 1.0 9.7 50-70 11.60 8.2 7.0 0.52 34.5 0.01 O.32 90-110 16.45 8.2 7.2 0.72 32.9 0.01 2.29 150-170 0.02 8.6 7.6 0.4-9 30.7 0.01 0.28 II 0-20 8.3 8.5 7.4 0.4-0 30.95 0.00 0.88 0.04 1.1 15.2 40-60 16.17 8.3 7.2 O.57 33.22 0.01 0.97 0.05 1.0 17.0 80-100 14.47 8.3 7.3 0.74- 31.69 0.01 0.90 120-140 8.30 8.2 7.2 0.4-1 30.11 0.00 0.77 160-180 18.72 8.6 7.4 0.51 31.50 0.01 0.93 III 0-17 4.46 8.1 7.2 11.01 37.2 0.26 I.63 0.08 2.0 50.0 17-32 5.31 8.2 7.2 6.2 5 28.8 0.11 0.35 2.0 50.0 32-48 7.86 8.2 7.2 4.24 33.5 0.08 0.37 50-70 18.40 8.2 7.2 5.27 39.2 0.13 0.35 70-90 18.77 7-9 6.8 5.86 43.4 0.16 0.53 120-140 10.12 8.2 7.2 O.58 31.3 0.01 0.35 CO CO L 10 < u M ph w & I —I I —I 3 5 .5 -P •rH PH 5 4h X X X 0 hrs 1 hr Time in Minutes oo -fr i i {b c/3 rh r f B5 i- B-ft ( D I t u O •s 8 H’ r+ VJ o 1 J 2 hrs 3 hrs (1) Reddish-yellow sand, deep carbonate. This occupies an area of 8 6 6.65 acres, or 29.8% of the total area at a depth of 120 centi meters . The soil is quite homogeneous. Phy s'i c al propertie s - - Tab 1 e 6-5 shows the poro sity to be from 37.3 to 39.6%; field capacity at 25%; the wilting point at 15.8%; and the average infiltration rate at 2.4 millimeters per minute. Chemical properties--Table 6-6 shows the pres ence of CaCOg along the whole profile depth. pH values range from 8 to 8.4. This soil is poor in humus, nitro gen, and phosphorus. Agricultural value--This type of soil has a lower value than the types described above. (3) Area No. 3: Bu-Argub Area The Bu-Argub irrigation system lies 2 0 kilometers north of the main dam with a total area of 450 acres. The pedological studies of this area are as follows: (1) Reddish-yellow sand on clayey sand carbonate. The total area covered is 82.5 acres. It has a shallow to medium deep surface layer of sand that is weak to medium round, stratified, and of a lighter mechanical composition. 85 Mechanical composition--This soil is character ized by a high percentage of fine sand and low clay con tent. See Table 6-7. Physical properties--This soil is quite homo geneous. Porosity ranges from 38.25 to 4-0.34-%; wilting point ranges from 4-. 15 to 8.89; infiltration rate is 3.56 millimeters per hour (see Figure 6-4). Table 6-8 shows the physical properties of this type of soil. Chemical properties--From Table 6-9 it can be seen that CaCO^ is variable, with the highest value at 12.7 3 and the lowest at 1.49. pH falls within 8.4 to 8.6, showing it to be weak in alkaline. Humus content is very low. This soil is not subject to the processes of salini zation and alkalinization. (2) Reddish-yellow sand, deep carbonate. This cov ers an area of 36 7.5 acres. The characteristics of this soil are homogeneous along the entire depth of the profile. Mechanical properties-^The quantity of fine sand is very high, ranging from 90 to 95%; clay ranges from 1.9 to 4.4%. Physical properties--The soil is homogeneous, with porosity from 38 to 39.9%; wilting point is 8%. The field capacity is 25% and the infiltration rate is 3.35 86 TABLE 6-7 SOIL TEXTURE OF BU-ARGUB AREA Description (percent) Sand Total Depth, Hygroscopic Profile Centimeters Coarse Fine Silt Clay Sand Clay Water Classification I 0-20 6.0 8 6.6 1.0 3 A 95.6 b A 0.72 Sand 3-50 k.5 93.6 0.7 1.2 98.1 1.9 0.^8 99 60-80 2.0 9^.0 1.^ 2.6 96.0 *K0 0.5^ 99 90-120 2.6 95.0 0.8 1.6 9 7.6 2A 0.50 99 130-150 2.6 9^.2 0.0 3.2 96.8 3-2 0.53 99 170-190 2.0 9^.0 1A 2.6 96.0 *K0 0 .^6 91 II 0-20 1.8 9^.0 0.1 *Kl 95.8 k .2 0.67 Sand 30-50 0.1 83.I 5.8 11.0 83.2 16.5 1.61 Clayey Sand 70-90 0.1 87.5 8.6 5.8 8 7.6 12 0.76 Clayey Sand 100-120 2.6 87.O 2.2 8.2 8^.6 10.^ '1.19 Sand 160-180 2.9 87.6 1.9 7.6 90.5 9.5 1M Sand 00 TABLE 6-8 SOIL PHYSICAL PROPERTIES OF BU-ARGUB AREA Depth, Profile Centimeters Hygro scopic Water Wilting Point, Percent Density, Grams per Cubic Centimeter Specific Spavity Porosity, Percent Field Capa city, Percent Permeability Coefficient, C entimeters per Second I 0-20 0.?2 5.25 2.60 2.6 38.84 25.13 9.2 X lCf3 30-50 0.^8 ^.83 2.62 2.62 ' 38.94 27.52 1.2 x 10~3 60-80 0. 5^ 5.03 2.63 2.63 38.99 26.48 2.1 x 10~3 90-120 0.50 4.72 2.63 3.63 38.00 25.87 5.8 x 10'3 0.50 2.62 2.82 39.70 26.40 1.77 x 15"3 00 00 TABLE 6-9 SOIL CHEMICAL PROPERTIES OF BU-ARGUB AREA Depth, Profile Centimeters CaCO Percent PH h2° KCl E.C. mhos per Centimeter at 2‘ 5°C Sat., Percent Salt, Percent Humus, Percent N, Percent p2°5’ Milli- grams k2° Percent I 0-20 2.77 8.4 7.3 0.93 28.3 0.01 0.52 0.03 2.4 M -.6 30-50 4.69 8.4 7.5 0.81 29.5 0.01 0.29 0.01 < 1 7-5 60-80 1.71 8.4 7.3 0. 8? 30.2 0.01 0.25 90-120 1.49 8.4 7.4 0.83 31.5 0.01 0.23 130-150 2.56 8.6 7.5 0.70 36.6 0.01 0.27 170-190 2.40 8.5 7.4 0.20 00 CD f-Capacity i n Millimeters per Minute Thrs 1 hr 0 hrs Time in Minutes FIGURE 6-4: Standard f-Capacity Curve of Bu-Argub Area millimeters per hour. Table 6~8 shows the physical prop erties of this soil. Chemical properties— -CaCOg is present along the whole depth. pH value is 8, indicating a weak alkaline reaction. Generally, this soil is poor in humus, nitrogen, and phosphorus. Table 6-9 shows all the chemical proper ties of this soil type. B. Consumptive Use From the soil classification map, 450 acres can be selected as good land for a full irrigation project. For any irrigation project the monthly consumptive use should first be determined. The consumption for a given area can be calculated using the Blaney-Criddle method. U = KF (6-1) U = consumption in inches for any period F = “ TOT— ( 6 - 2 ) t = mean monthly temperature in °F P = monthly percent of day time hours of the year K = empirical coefficient function of irrigation season or growing period Computation of (K) from observed data for normal water supplies and growing seasons gives values for irri gated crops in arid and semi-arid areas, as shown in 91 Table 6-10. The yearly consumption is 51 inches. Irrigation r:_r * • consumptive use n rn efficiency = — -x— —^ n « ■■— — -*■ = 0.67. J water delivered Water delivered = 7 6.1 acre inches per year 6 Volume of water required for irrigation = 3.6 x 10 millions of cubic meters The percentage of water required for irrigation = 3-6 x 106 = 3_4 10.5 x lO6 Percent of infiltration losses in the dam basin = 26% Evaporation losses = 7% Total losses = 0.26 + 0.07 = 33% Water available for irrigation and recharging system = 67% Water available for recharging project = 0.67 - 0.34 = 33% C. Irrigation System A main pipe line - 2 8.2 5 kilometers in length will be connected from the valve house at the main dam passing through the center of the proposed area, as shown in Fig ure 6-5. The advantages of this method are that the head difference can be used for sprinkling without additional pumps, and that losses from evaporation can be cut. Main tenance in the case of closed conduct is much easier than 92 with channel conduct because of the prevailing sandy wind in the summer season! This system will serve a double purpose during the wet year, where the extra water will be drained into the wadi bedlto carry on to the infiltration basins. 1. Hydraulic calculations 0.5 V,2 V,2 z i + ~2g— - = z2 + 2ir + h f ( 5 ‘ 3) 2 V ^ / 1 7 ry ^ j . / 0 . 5 2 , _ ^ (Z1 Z2) ( 2g 2g ) " f Head drop between A and B 264 - 220 = 44 meters From equation (6-3) hf = 44 + (°~ 5 1------2---) (6-4) 2g A 2g A Z The required inflow for 270 working days is: 4 6 v in 9 Q = — 1- — y j q = 1666.7 cubic meters per day = 9.24 cubic feet per second Substituting in equation (6-4) for Q values: h = 44 x 3.3 - Q,5(9,21|)---r2--9 f 2 x 32. 3(-^--) hf = 145.2 - (9--— j ^-1— 4 x 32.2 7r2d4 93 1 0 7 h = 145.2 - " 1 d fLV2 c, f 2gd ( J where f is the coefficient of pipe friction and is assumed to be equal to 0.02 for steel pipe; L., pipe length in feet; V, water velocity in pipe in feet per second; d, pipe diameter in inches; and g, the acceleration of gravity (32.2 feet per second per second). By substituting in equation (6-5): , n no 28250 x 3.3 x (9.24)2 h.p = 0.02 x ------------------ , 2 x 32.2 x d x( 1214.3x3.3 d6 0 0 1. 07 1214. 3 x 3 .3 44 x 3.3 - --r— = — ----- e------ d4 d5 44 x 3.3 - 1214-3 x 3-3 + 1.07 d5 ,5 1214.3 d = 44 d = y} 27 . 6 d = 1.94 feet use 0 =25 inches Head drop from B to C is 220 - 135 = 85 meters 9.4 Head loss per 10 0 0 feet = — 2 ” ^ ‘ ^ fee_t per 10 0 0 feet 9 24 . Q = 2 _'~'5S ~ millions of gallons per day By/.using the chart (Figure 6-6) and for C = 100, head loss = 4.8 feet per 1000 feet, and Q (discharge) = 5.91 millions of gallons per day This gives d = 20 inches FIGURE 6-6: Nomo-Graph Hazen-Williams Formula, C-^ = 100 200 150. 100. 50_J 40. 30 d 20 15 10. id 0.5 0.4 0.3 0.2 - 0.1- 03 o J- LO II 8 £ 60-i 54 48- 42- 36- 30- 24- 20- 16- 12- 10- 8- 6 4-J 03 I ■n a •H Q £ o o o it ; .g C/3 % rS 0.05 !0.07 P o.io -0.15 -0.20 J3.30 0.40 -0.50 JO .70 - 1.0 I —1..50 = —2.0 -3.0 4.0 -5.0 —8.0 -10.0 i-15.0 -20.0 P-30.0 40.0 t-50.0 L-100.0 96 TABLE 6-10 SEASONAL CONSUMPTIVE USE COEFFICIENTS (k) Consumptive Use Crop_____________ Length of Growing Season______ Coefficient (K) Alfalfa Between frosts 0.85 Beans 3 months 0.70 Corn ^ months 0.85 Grains 3 months 0.85 Orchard: Citrus 7 months 0.65 Pasture Grass Between frosts 0.75 Potatoes ^ months 0.75 Tomatoes 3 months 0.70 V egetahles 3 months 0.60 TABLE 6-11 MEAN MONTHLY TEMPERATURE (t), PERCENT OF DAY TIME HOURS (P), CONSUMPTIVE USE FACTOR (f), AND COMPUTED CONSUMPTIVE USE (u) Month Mean Temperatures (t) in °F Percent of Day Hours (P) Consumptive Factor (f)* Consumptive Use (u)** January 48.3 7.17 3.^6 1.0 February 51.9 6.95 3.61 2.0 March 56.9 8.36 4.76 3.5 April 67.3 8.77 5.90 5.0 May 73.6 9.66 7.11 6.5 June 82.1 9.62 7.90 9.0 July 89.3 9.80 8.75 12.0 September 82.6 8. 3^ 6.89 36.0 October 68.6 7.92 5 A 3 b.o November 54.7 7.09 3.88 3.0 December 50.6 7.02 3.55 2.0 TOTAL 69.OO 51.01 * f = t x p 100 **u = KF 98 VII, GROUND WATER STORAGE PROJECT A. Annual Runoff In Chapter I the average annual runoff of the wadi was estimated to be as much as 10.5 million cubic meters. This average cannot be taken into consideration in design ing any recharge project because the wadi runoff varies from year to year. According to Table 7-1, the yearly runoff for the 29 years from 1944 to 1973 can be classified by wet and dry values. It can be seen that in any year, 4.5 million cubic meters of runoff can be expected. Thus, the re charging system should be based on that quantity. In the case of a wet season where the runoff is more than the capacity of the recharging system, the extra runoff can be kept in the surface reservoir, which has a capacity of more than 3 0 million cubic meters. An operational pro cess can be set up through the outlet conduit from the reservoir to the recharging area. Time tables should be based on daily infiltration of the recharging system so that the water from the reservoir can be easily sent to the recharge area. To estimate the rate of infiltration along the wadi 99 TABLE 7-1 YEARLY RUNOFF IN CUBIC METERS OF WADI ELMEGENIN (1944-73) Runoff in No. Year Cubic Meters 1 1 9 ^ -4 5 10,022,000 2 1945-46 18,840,000 3 1946-47 3,682,000 4 1947-48 1,372,000 5 1948-49 14,162,000 6 1949-50 15, 031,000 7 1950-51 10,625,000 8 1951-52 21,041,000 9 1952-53 2,825,000 10 1953-54 2,194,000 11 1954-55 17,317,000 12 1955-56 9,855,000 13 1956-57 16,901,000 1957-58 4,638,000 15 1958-59 6,242,000 16 1959-60 1,986,000 17 1960-61 7,822,000 18 1961-62 22,801,000 19 1962-63 15,725,000 20 1963-64 20,844,000 21 1964-65 11,262,000 22 1965-66 12,133,000 23 1966-67 8,810,000 24 1967-68 9,100,000 25 1968-69 2,000,000 26 1969-70 9,000,000 27 1970-71 3,760,000 28 1971-72 12,100,000 29 1972-73 7,198,000 TOTAL 299.290.000 MEAN 10,320.000 ---------L s d--2 --- 100 bed, the following measurements were taken under the same time and temperature conditions: Date Measuring Station Length of Reach in Kilo meters Flow in Cubic Meters per Second Infiltra tion in Cubic Meters per Second Infiltration in Cubic Meters per Hour per Kilometer 9-26-65 Morabito Ben Ghishir 17.9 4.4 2.5 1.9 382.12 9-26-65 Ben Ghishir 28.7 2.5 Bab Azizia 0.2 2.3 288.5 The width of the wadi at the Morabito Bridge and Ben Ghi- shir Bridge is about 22 meters, with a slope of 3.01%. The width between the Ben Ghishir and Bab Azizia Bridges is about 150 meters, with a slope of 3.2%. 1. Infiltration between Amoit Intake and Morabito Bridge This profile was. assumed to be the same as between Amoit intake and Sidi Gelani, as follows: Date Length of Reach Measuring in Kilo- Station meters Flow in Infiltra- Infiltration Cubic tion in in Cubic Meters Cubic Meters per per Meters per Hour per Second Second Kilometer Duration in Hours 4-29-55 D-S Amoit 6.5 U-S Gelani 55 54 1 553.85 18 101 The wadi bed at this profile has a width ranging from 10 meters to 360 meters; it is generally flat and not deep. Extra runoff comes mainly from the rocky hills in the area. The extra runoff is distributed as follows: Between the dam and Amoit 2 8 square kilometers Between Amoit and Sidi Gelani 12.7 3 1 4 . 95 TOTAL 7 5.6 square kilometers The average yearly runoff from this area is 1.24 million cubic meters. Therefore, the profile should be used to hold this extra runoff, which will them be diverted through existing diversion channels to the old recharging basin at Bu-Argub. A comparison of infiltration rates for the four profiles has been shown in Figure 3-7, illustrating that the profile between Morabite Bridge and Ben Ghishir Bridge has the highest infiltration rate. At the same time, the ground water decline is the most significant. It can be seen that this is a very good recharging region, and any type of artificial recharging should be located within this profile. B. Silt 'Content in the Surface Water The presence of silt in water has a negative ef fect on the infiltration rate. For this reason, at any 102 time runoff occurs, the silt content of the system should be determined. The allowable silt content in the water is diverted for spreading varied quantities from one project to another and usually .has a maximum limit of between 1000 and 10,000 ppm. A periodic measurement of silt content has been taken in three check dams loca ted upstream and forming the main tributaries of the reservoir (W. Hammam; W. Hasi; W. Alwar). As shown in Figure 7-1, these wadies control 68% of the total Wadi Elmegenin basin surface. Measurement of the volume of deposited sediments in the main reservoir during the years 19 71-7 2 and 19 7 2- 7 3 was made by gauging the cross-section in Figure 7-1. These measurements were taken before and after the rainy season and.are shown in Table 7-3. With an average runoff of 10.32 millions of cubic meters, the amount of silt would be 267,800 cubic meters, or 267,800 x 1.33 = 302,600 tons per year. The reservoir should be cleaned yearly during the dry period to prevent bottom sealing of the reservoir, which will affect the infiltration rate in the reservoir basin. 1. Sediment grain size The sediment deposited in the reservoir is 103 Scale 1:50,000 V & ' t f CL H- ✓ CD 00 rf K f s ' Cl H- 00 ')l J l CD C / D rt / \ CD f t ^ CL fu a CL P j p . Hi ^L CL £ EC s > . r r t h. CD co r+ f —1 C D pJ C D H 5^c v v\^p FIGURE 7-1 LOCATION OF CHECK PROFILE AND HYDROLOGIC STATIONS \ 104 TABLE 7-2 RUNOFF CLASSIFICATION Type Volume of Water in Millions of Cubic Meters Occurrence (years) Very wet year More than 15*2 7 Wet year More than 10.5 6 Dry year Less than 10.5 9 Extremely dry year Less than 4.5 7 TOTAL 29 years TABLE 7-3 PERCENT OF SILT CONTENT IN THE RUNOFF Year Runoff in Silt in Percent of Cubic Meters Gubic Meters Silt Content 1971-72 12,100,000 350,417 2.9 1972-73 7,198,000 165,811 2.6 AVERAGE Zj2 105 generally: very fine-,, No particles were found in any sam ple coarser than 0.5 millimeters (see curve I, Figure 7-2). It can be concluded that 75% of the total sedi ments are silt and fine clay less than 0.02 millimeters. Curve II shows that the amount of suspended materials at the surface of the reservoir during the inflow period consisted of 1.3% fine sand (0.02 - 0.5 millimeters) and 8 7% fine silt and clay (less than 0.02 millimeters). Curves 11^ and Ilg represent deposit sediments in the reservoir during 1971-72 and 1972-73. It is clear that these suspended materials will be carried out with the outflow during the operation period; for this reason it is recommended that the flow be kept in.Jthe reservoir for a few days until all the suspended material settles down. After that, the water can be carried out for irri gation and recharging. In Chapter IV, factors were listed which must be considered in selecting the proper sites for artificial recharge. These factors are based on an evaluation of surface material as it controls the infiltration rates and physical characteristics of underlying material for most efficient utilization of storage capacity and trans- missibility of the aquifer. In many cases, water table decline also dictates the recharging sites. 106 107 g rain ;' D iam eter-in~diirTH m 0.002 02001 30 20 200 100 60 Suspended load inlet in FIGURE 7-2• reservoir, 1972-73 Suspended load in reservoir (near lake surface) 1971-72 Deposited sediment from bottom-set beds, 1971-72 "Deposited sediment from bottom-set beds, 1972—73 Typical Curves, Grain Size Distribu tion for Wadi Elmegenin Main Dam Reservoir, on the Basis of Measure ments in 1972 and 1973 2. Natural stream bed infiltration Infiltration along the Wadi Elmegenin bed was estimated on the flow of the following profiles: Bab Azizia Bridge M-, 0 kilometers from the sea Ben Ghishir Bridge 32.7 Morabito Bridge 5 0.7 Amoit intake 7 2.3 Dam site 8 5.9 3. Ground water level in the recharge area The ground water level in the selected area (Morabito Bridge and Ben Ghishir Bridge) is from 30 to 65 meters with a slope of 1.11 meters per kilometer. Figure 7-3 represents the ground water contour lines in the mentioned area. 4. Ground water quality in the recharge area Total dissolved substances 1045 ppm Cl 100-300 ppm SO^ 235 ppm C03 236 ppm Figure 7-4 shows the contour lines of the chlor ine content in the ground water, as ppm. 5. Surface water quality Total dissolved substances 116 ppm Cl 7 ppm SO^ 2 0 ppm CC>3 9 3 ppm 108 .Morabito V SCALE 1:100,000 50 Meters 40 Meter \ •Ben Ghishir \ FIGURE 7-3 Ground Water Elevation in Meters in the Recharge Area 109 Morabito ; o FIGURE. 7-4: Chlorine Content in ppm in the Ground Water in the Recharge Area 110 6, Geological formation of the proposed area Surface sand covers the area with a depth of 10 meters underlain by fissured sandstone. This type of formation makes a very good ground water reservoir, hav ing the advantages of a high infiltration rate and high specific yield, 7. Type of recharge system The natural stream bed basins are selected for simplicity, economical^construction, and easy opera tion and maintenance of the system. Three dikes should be constructed in the area be tween. '.Morabito Bridge and Ben Ghishir Bridge where the highest rate of infiltration was measured. These dikes are built from river bed materials and have very wide bases to prevent collapse; the abutments and spillways of these interbasins control the structure and are made of concrete. It has been found that greater flexibility of operation and maintenance can be achieved by using a mini mum of three dikes. This factor is important in continu ous spreading projects because it permits the project to remain in operation during periods when spreading must be discontinued and basins dried for maintenance and re establishment of infiltration rates. Multibasin opera- 111 tion provides that the first basin can beautilized as a sedimentation pond to remove silt, which is one of.the more serious problems* The upper pond should be large enough to substantially reduce the velocity of flow. Figure 7-5 shows the dike arrangement. 8. Operation and maintenance procedures Silt: (1) The water should be kept in the main reservoir for at least one week to settle the suspended sediment before taking water to the recharge basins, (2) The harrow and disc should be scraped after proper drying. (3) Silt should be removed after drying. Rodents: (1) Set out poison twice a year. Public health and safety: (1) Area should be fenced. (2) Patrol area before and during operation, with particular attention to children and struc tural failures. (3) Post proper signs when using poisonous chemicals. 112 Maintaining infiltration rate; (1) Use chlorine or copper sulfate for control of bacterial slime and algae. (2) Soil can be reconditioned by using organic materials such as cotton-gin trash or chemi cal agents such as krilium. 113 Volume of Basin #1 19,500 Volume of Basin #2 340,475 Volume of Basin #3 Total volume 374,2 75 cubic meters Dam #2 8** Dam #3 FIGURE 7-5; Dike Arrangement for Recharging System VIII. CONCLUSION Since Libya is completely dependent upon rain and ground water for its water supply and agricultural pro jects, it is very important that storms be captured during the winter rainy seasons by constructing dams or recharging basins in the catchment areas. In this way, two goals can be achieved: (1) increasing ground water storage, and (2) utilizing surface water for irrigation projects. The first goal, the replenishment of ground water storage by artificial means, can be accomplished by either of two general methods: (1) spreading water over the land and letting it infiltrate into the soil and percolate down ward until it reaches the ground water table, or (2) di verting water into wells, shafts, or pits from which it can infiltrate to the water table. Surface spreading can be done by basin, modified stream bed, furrow, ditch, or flooding method. The basin method of surface spreading is the most commonly used be cause of its operational flexibility. The water can be controlled very easily. Basins can be arranged so that the uppermost basin of the system is a settling pond. The utilization of stream channels represents an effi- 115 cient and economical method of artificial recharge. This can be accomplished by small check dams and dikes which reduce velocity and spread the flow over the entire width of the channel to attain maximum infiltration. These structures may be permanent, or simply temporary earth fill. In this thesis, the modified stream bed type has been selected for the Wadi Elmegenin artificial recharge project, by building three permanent dikes in the profile between Morabito Bridge and Ben Ghishir Bridge. The three basins have a total capacity of 37 4,27 5 cubic meters with an in filtration rate of 1.24 meters per day. This method has the advantages of flexibility of operation and economical construction. 116 REFERENCES Books 1. Butler, S,S., Engineering Hydrology. Prentice-Hall, Inc, , Englewood”Cliffs'^ NJ (19 5 7 ), 2. Chow, V.T., Hydrology Handbook. McGraw-Hill, Inc., New York, NY (19 64“ ). 3. Tolman, C.E., Groundwater. McGraw-Hill, Inc., New York, NY (1973). Government Publications 4. Libyan Arab Republic, "Soil and Water Resources Survey for Hydro-Agricultural Development." Hydrology G.E.F.L.I., Vol. 23.(Nov. 1972). 5. Libyan Arab Republic, "Soil and Water Resources Survey for Hydro-Agricultural Development." Hydrogeology G.E .F.L.I., Vol. 24 (Nov. 1972). 6. Libyan Arab Republic, "Wadi Elmegenin Project Basic Investigation and Studies." Hydrology Hydro-Project, Vol. 1 (1973). 7. U.S. Department of Agriculture, "Replenishment of Groundwater Supplies by Artificial Means." Tech. Bull. No. 1195 (Feb. 1959). 8. U.S. Department of the Interior, Geological Survey, "Artificial Recharge of Ground Water: An Annotated Bibliography through 1954." Water Supply Paper No. 1477 (1959). Publications of Technical Societies 9. Bauman, P., "Groundwater Movement Controlled through Spreading." American Society of Civil Engineers Transactions^ Vol. 117, Paper No. 252 5 (19 5 2TT 10. Bennison, E.W,, "Replenishment of Groundwater Sup- * . plies." American Water Works Association Journal, 41, 2 (Feb. 1949). 117 11. Blaney, H.F., "Monthly Consumptive Use Requirement for Irrigated Crops," A. SVC .E, 8 5 , ■ IR 1 (March 1954). 12. Bliss* E.S. and C,E. Johnson, "Some Factors Involved in Groundwater Replenishment." American Geophysica1 Union Transactions, 3 3, 4 (Aug. 1952). 13. Conkling, H., "Utilization of Groundwater Storage in Stream System Development,” A.S.C.EY Transactions, 111, Paper No. 2272 (1946). 14. Erickson, E.T., "Using Runoff for Groundwater Re charge." American Water Works Association Journal, 41; ' 647-49 (July 1949). ' ~ “ 15. Hill, R.A. and N.D. Whitman, Jr., "Percolation from Surface Streams." American Geophysical Union Trans actions , 36, 6 (Dec. 1955 ) . 16. Laverty, F.B., "Groundwater Recharge." American Water Works Association Journal, 44, 8 (Aug. 1952 ) . 17. Muckel, D.C., "Research in Water Spreading." A.S.C.E. Separate No. Ill (Dec. 19 51). 18. Richter, R.C. and R.Y.D. Chun, "Artificial Recharge of Groundwater Reservoirs in California.” A.S.C.E., 58, IR 4 (Dec. 1954). 19. Schiff, L., "The Status of Water Spreading for Ground Water Replenishment." American Geophysical Union Transactions, 36, 6 (Dec. 19 5 5) 20. Simpson, T.R., "Utilization of Groundwater in Cali fornia.” A.S.C.E., 117, Paper No. 2522 (1952). 21. Task Group E4-B on Artificial Groundwater Recharge. 22. Thomas, H.E., "Artificial Recharge of Groundwater by the City of Bountiful, Utah." American Geophysical Union Transactions, 30, 4:(1949). 23. Todd, D.K,, "Economies of Groundwater Recharge." A.S.C.E., 91, HY-4 (July 1965), 118 Periodical Article s . 24, Allison, L,E,, "Effect of Micro-Organisms on Permea bility of Soil Under Prolonged Submergence," Soil Science, 6 3: 439-50 (June 1947), 25, Barksdale, H.E, and D.B. George, "Artificial Re charge of Productive Groundwater Aquifer in New Jersey." Economic Geology, 41: 726-37 (1946). 26, Christiansen, J.E., "Effect of Entrapped Air Upon the Permeability of Soils." Soil Science, 58: 644-5 8 (1946). ' 27, Meinzer, O.E., "General Principles of Artificial Ground Water Recharge." Economic Geology, 41: 191-2 01 (1946 ) . 28, Scott, V.H. and G. Aron, Groundwater, 5, 3 (July 1964). 119 30‘ T'33;1 3,0 t z 2 BEN-GHASHIR HOSH v_ . KHITNAH y O o ro c j i X GHARYAN m m o m m ICO t ! = f \ L O \ CD 1-1 Ras Hamia Formation 2-2 Azizia Formation Abu Shaybah Formation vBu Geilan Kiklah Aintobi ‘ ____ 7-7 Garyan .8-8 Tertiary 9-9 Quaternary , 10-10 Volcanic V -______Faults WADI EL MEGENIN I : 100000 GEOLOGICAL MAP M k ^ ‘1 r ZAULA 300 mm' 100 mm OMS AZtZTA t a r h u n a 2 LI TEN 200 m m 100m SUQ GMATAH _ __ • 1E 0 mm — ■ GIQSC GilAD NZLUL 'gENI ULSO _ \ _ MIZDA Fig.2 -4 ISOHYETAL MAP OF TRIPOLI UU'J V m m T r r T m T c-fek./, ;?ui 77777 ? f'/vA7] / 7 'sry N y % 7 / 7 / , ? /. ip^ l> 'i LEGEND: 1 7 7 7 7 1 V e ry good s o i l "7 7° < / o \ Soil with hummock ( Z Z Z Z J Poor soil with shallow soil SS Movable sand FIGURE 6-1 WADI EL MEGENIN D R A W N BY APPROVED BY :5 0000 SOIL RECONAISSANCE MAP O R A W IN a n u m o e m (.LUit B IN GHiSHiR WADI EL MEGENIN '' .^S S S V S S l' ^S frJi DATE (g74 DRAWN BY 1 APPROVED BY | SCALE | . 100000 REVISED , | IRREGATION PIPELINE AND RECHARGE BASINS SITE DR A W *M O N U W I f w a,»BWJUMmai FIGURE 3-8: GROUND WATER CONTOUR LINES MEDITERRANEAN SEA TRIPOLI • SWAN I BENVAD BEN- GHASH^R • AZIZIA RESERVOIR BU-AEK5UB SID - GELAN /A M O IT ALKHITNA GHARYAN

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Asset Metadata

Creator Matoug, Mohamed Ibrahim (author)

Core Title Wadi Elmegenin artificial ground water recharge

Degree Master of Science

Degree Program Civil Engineering (Water Resources)

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

Tag engineering, environmental,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Butler, Stanley S. (committee chair), Lee, Jiin-Jen (committee member), Merriam, Richard H. (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c20-327734

Unique identifier UC11260183

Identifier EP41994.pdf (filename),usctheses-c20-327734 (legacy record id)

Legacy Identifier EP41994.pdf

Dmrecord 327734

Document Type Thesis

Rights Matoug, Mohamed Ibrahim

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA