Consulting Services for Detailed Design and Tender Documents of Effluent Recovery and Irrigation Scheme of North Gaza Emergency Sewage Treatment Contract Number: NGEST/AF-QCBS01-08/DD Concerning Irrigation Scheme Consultant Joint Venture Association of the Center for Engineering and Planning (CEP) and the FCG International Ltd. June 2010 1
Concerning Irrigation Scheme 1. Project Background and Objectives: The main objective of the current project is to design recovery wells, water storage tanks, pump station and irrigation networks which should account for possible infiltrated wastewater, recovery scheme, and the demand for crops up to year 2025 or 2030 (based on consultant prediction) which could reach the identified capacities of treated wastewater (69,000 m 3 /day). Two phases based on generated wastewater quantity (35,600 m 3 /d and 69,000 m 3 /d) regardless of the target year (around 2012 and 2025) will be considered. Detail design of the recovery scheme is for 35,600 m 3 /day as infiltrated treated wastewater. Future extension of infiltration basins and recovery scheme to accommodate 69,000 m 3 /day of treated wastewater will be suggested. The main factors influencing the design scheme are: i. The quality of treated wastewater (treated and partially treated) diverted to the infiltration basin depends on the efficiency of the treatment in the existing Basin Wastewater Treatment Plant (BWWTP) and/or the construction of the North Gaza Emergency Sewage Treatment. ii. The cropping patterns water demand. To ensure the capturing of all infiltrated water quantity, an addition 10% extra over the infiltrated amount should be abstracted. Yearly infiltrated treated wastewater should be recovered and used at the same year. The recovered 35,600 m 3 /day, with 10% extra, should be used for irrigation in the vicinity or nearby area of the recovery wells (Figure 1), therefore, the current document should specify: - land availability (total area required), - cropping patterns, - daily and monthly crop water requirement, and - irrigation methods 2
2. Agriculture Background for Project Area: The total project area is around 15,700 dunum located on North East of Gaza Strip adjacent to the eastern border with Israel as shown in Figure (1). The agricultural area is about 12,600 dunum whereas the industrial and residential area account for 3000 dunum. The proposed area is divided into two zones (A and B) according to its location from infiltration basins. Zone A is the part located north of infiltration basins with about 10,100 dunum whereas, Zone B is located south of proposed WWTP with about 5,000 dunum (Figure 1). Zone A Zone B The location of infiltration basins and Recovery wells Figure (1): Project Site Map. 3. Climate Data for Project Area: Gaza Strip is located at the east shore of the Mediterranean Sea. It is considered as a semiarid region with an annual rainfall ranging from 200 to 450 mm. The meteorological factors determining evapotranspiration are weather parameters which provide energy for vaporization and remove water vapour from the evaporating surface. The principal weather parameters to consider are: solar radiation, wind speed, air humidity and air temperature. Rainfall: The main rainfall season in the proposed area is from October to March. The average rainfall rates range from 0 mm in summer months to its maximum in December and January, however it differs from year to year (Table 1). 3
Sunshine hours: Solar radiation is the largest energy source available and is the main driving force for the vaporization of water which determine the evapotranspiration process. Actual sunshine hours are relatively high in summer months being about 11 hours daily. While, potential sunshine hours around 8 hours daily. Air temperature: The solar radiation absorbed by the atmosphere increases the air temperature which transfers energy to the crop and exerts as such a controlling influence on the rate of evapotranspiration. In sunny, warm weather the loss of water by evapotranspiration is greater than in cloudy and cool weather. The project area is considered as temperate region so the average minimum temperature around 10 C in January to maximum temperature around 30 C in August taking in to account the climate change through the mentioned ten years (1.5 C/year). Relative humidity: While the energy supply from the sun and surrounding air is the main driving force for the vaporization of water, the difference between the water vapour pressure at the evapotranspiring surface and the surrounding air is the determining factor for the vapour removal. The project area is far from Gaza shore and therefore the relative humidity is relatively medium ranging from 60 to 75 %. Wind speed: The process of vapour removal depends to a large extent on wind and air turbulence which transfers large quantities of air over the evaporating surface. When vaporizing water, the air above the evaporating surface becomes gradually saturated with water vapour. If this air is not continuously replaced with drier air, the driving force for water vapour removal and the evapotranspiration rate decreases. The wind speed is about the same during the year with an average 10.4 km/hr. The evaporation power of the atmosphere is expressed by the reference crop evapotranspiration (ET o ). The reference crop evapotranspiration represents the evapotranspiration from a standardized vegetated surface. Table 2 illustrates rainfall, temperature, relative humidity, wind and sunshine hour's for ten years (1997-2006) average values for the project area. 4
Table (1): Monthly Rainfall Average for Gaza Station (mm) (2000-2007) Season 2000-2001 2001-2002 2002-2003 2004-2005 2005-2006 2006-2007 AVG Rainfall JAN 130.4 17.8 98.1 53.5 106.6 159.5 94.3 FEB 60.6 11.8 239.4 46.1 16.8 98.8 78.9 MAR 10.5 12.1 67.9 33.2 21.7 68.5 35.7 APR 3.2 6.6 9.2 0.2 42.5 1.7 10.6 MAY 0 0 0 0 0 0.8 0.1 JUN 0 0 0 0 0 0 0.00 JUL 0 0 0 0 0 0 0.00 AUG 0 0 0 0 0 0 0.00 SEP 1.2 75.6 0 0 0 2.2 13.2 OCT 132.3 23.7 38.8 0.1 19.7 40.8 42.6 NOV 17.6 198.3 6.7 104 56.4 27.8 68.5 DEC 132.5 202.4 163.2 52.1 51.4 84.9 114.4 Table (2): Climatic Data of Project Area in Average (1997-2006) (Meteorological Gaza Office, 2006) Month Rainfall (mm) Min Temp C Max Temp C Relative Humidity % Wind (km/hr) Sunshine (hours) Jan 94.3 10.8 18.1 65 11.3 4.8 Feb 78.9 11 18.2 67 12.3 6.1 Mar 35.7 12.9 19.8 67 11.5 7.6 Apr 10.6 16.3 22.9 67 11.0 8.4 May 0.1 19 24.6 72 10.2 9.7 Jun 0 21.7 27.2 74 9.8 9.8 Jul 0 23.8 29.6 74 9.7 10.7 Aug 0 24.5 30.2 72 10.1 10.6 Sep 13.2 23 29 68 10.5 9.7 Oct 42.6 20.3 26.7 67 10.5 8.3 Nov 68.5 16.3 23.5 62 10.6 6.2 Dec 114.4 12.6 19.6 64 10.9 4 Average 38.2 17.7 24.1 68 10.7 8 5
4. Soil Type of the Project Area: In general, the dominate soil type in the area can be considered as heavy soil with deep soil profile, which means that the hardpan of soil profile is far away from the soil surface. Thus, hardpan and/or parent material will not limit roots penetration for deep rooted crops. Detailed soil characteristics (physical and chemical) will be investigated in the second phase of the project. Zone A Zone B Loamy clay textured soils with dark brown to reddish brown color are dominated in the area (Figure 2). The calcium carbonate content ranges from 15 to 20% (MOA, 1994). The north part of this area is loamy clay textured soil and the south part is loess textured soil and is yellow brown in color as shown in Figure (2). Zone A Zone B Figure (2): Gaza strip soil map and project area (MOA, 1994) The soil texture of the project area was first determined through soil investigation and reported in the soil report. The soil investigation showed that the texture of soils differs from loam to sandy loam. 6
5. Existing Agricultural Situation in Project Area The data about the existing agricultural situation in the proposed project area was collected during site visits. The proposed area is actually cultivated with different crops: citrus, olives, fruits, grains and vegetables. The survey includes also the number and ownership of farms in each zone, crops type and their respective irrigation systems, (Table 3). Surface irrigation is common and irrigation system is predominated in the grooves. Table (3): Land survey (December, 2009). No. Of Property Crop Total Areas (du) Farms Private Awqaf Rainfed 12055 398 379 19 Citrus 688 68 68 0 Olives 600 58 57 1 Unfruitable Citrus 510 69 69 0 Unfruitable Olives 14 3 3 0 Vegetables 280 32 30 2 Fruits 184 11 10 1 Almond 53 5 5 0 Total 14384 644 621 23 Distribution of cultivated crops in the project area Table (4) shows the distributions of cultivated crops in both zones (A & B). Most of the area (about 12,000 dunum) is considered as area under rain-fed conditions which includes mainly the demolished area and area cultivated with grains. This area would benefit from available reclaimed water and turn from rainfed farming to irrigated land. Table (4): Distribution of cultivated crops in zone (A & B) (Dec. 2009). Crops Zone A (dunum) Zone B (dunum) Total Rain-fed 7593 4462 12055 Citrus 515 172 688 Olives 388 212 600 Vegetables 260 20 280 Fruit Trees 120 0 120 Almonds 53 64 117 Citrus (non-fruitable) 464 46 510 Olives (non-fruitable) 14 0 14 Total 9407 4976 14,384 7
Citrus is a crop grown in the project area with an area of 1198 dunum (fruitable and nonefruitable). However, citrus is sensitive to poor groundwater quality (mainly salinity) resulting in reduced yields and quality with some plantations being abandoned. Olives represent 614 dunum (fruitable and none-fruitable). Vegetables represent 280 dunum. The area of fruit trees is 120 dunum, whereas, the rainfed area includes the grains and the demolished area occupying the most of the project area being 12,055 dunum as shown in Figure(3). Figure (3): Existing crops in project area. The water requirements for the different crops were calculated using local climatic parameters. Crop coefficients were obtained from FAO Irrigation and Drainage Paper No. 33. The net irrigation requirement for crops was calculated using crop evapotranspiration (ET) and effective rainfall according to Cropwat V.8, 2009. Leaching requirement will be discussed in the section of cropping pattern design. 8
6. Criteria for crop selection Self Sufficiency: Gaza Strip is actually in bad need to citrus, olives and fodder crops. Policy of Ministry of Agriculture Dominant crops: These lands -especially the north part- was previously cultivated with citrus. Farmers' acceptance: The farmers are familiar with citrus and vegetables cultivation. Reclaimed Water quality: The infiltrated water is actually partially treated, and its quality is expected to improve through soil filtration. Climate and land suitability. Crop value and market availability. 7. Irrigation Water Demand The irrigation water demand has been determined based on the following factors: Type and percentage of crops in the project area. Climate in the project area (rainfall, temperature, relative humidity, etc.) taking the climate changes in consideration. Soil characteristics as given in the attached agricultural soil testing report. Irrigation methods. Table (5) illustrates the monthly crops water requirements calculated using (Cropwat V. 8, 2009) software. Considering effective precipitation calculated as 80% of total precipitation (Cropwat V. 8, 2009) Table(5): Monthly Crops Water Requirements (mm) (Cropwat V.8, 2009) Month Citrus Olives Fruit Alfalfa Vegetables Grains Jan. 12.1 1.3 0.6 40.7 8.2 48.5 Feb. 17.2 4.8 1.4 11.0 16.8 19.4 Mar. 35.0 8.5 12.8 29.8 56.1 10.1 Apr. 67.0 35.5 40.5 60.7 111.2 108.2 May 89.8 53.3 60.9 87.9 140.0 166.3 June 98.8 60.5 71.6 115.0 145.1 123.0 July 115.6 72.9 88.6 154.8 132.3 6.1 Aug. 117.6 74.6 91.8 180.8 77.1 0.0 Sept. 92.2 54.8 69.8 157.1 67.4 0.0 Oct. 68.2 37.2 49.6 122.3 80.8 0.0 Nov. 38.8 15.2 24.2 80.8 57.1 13.6 Dec. 7.7 0.0 0.2 43.4 9.9 40.0 Total 760.0 418.6 512.0 1084.3 902.0 535.2 9
8. Calculation of leaching requirements The leaching requirement is the ratio of the net depth of leaching water to the net depth of water which must be applied for consumptive use. Calculating the leaching requirement for trickle irrigation is greatly simplified by: Where: ECw = Irrigation water salinity, ds/m ECd = Drainage water salinity, ds/m ECw LR = ECd ECd can equal 2 (max ECe) Then LR can be calculated for trickle irrigation percent as: ECw LR = 2max ECe Where: Max ECe = electrical conductivity of the saturated soil extract that will reduce crop yield, to zero, ds/m. (Sprinkler and Trickle Irrigation by Bliesner and Keller, 2001) However, for sprinkler and surface irrigation systems, leaching requirement calculated using the following equation: ECw LR = 5 ECe ECw Where ECe is estimated electrical conductivity of the average saturation extract of the soil root zone profile for an approximate yields reduction, ds/m. ECe values which will give 10% yield reduction is recommended (Annex 1) Table (6) illustrates Leaching requirement (ratio, %) Drip, sprinkler and surface irrigation systems. Table (6): Calculation of leaching requirements. Crop Citrus and Fruit tress Olive trees Alfalfa Grains Weighted Average ECw, ds/m (1) 2.925 2.925 2.925 2.925 2.925 ECe, ds/m (2) 2.3 3.8 3.4 7.4 - Sprinkler and surface irrigation systems, LR, % 34.1 18.2 20.8 8.6 45 Relative proposed area for scenario III 45 25 15 15 100 LR calculated on weighted value % (3) 15.35 4.55 3.12 1.29 24.30 (1) Source: analysis of local wells. (2) Source: FAO and presented in Annex 1 (3) Numbers in the shaded cells represent applicable leaching requirement. 10
Based on recommended cropping pattern, recommended irrigation system for each crop, and expected reclaimed water quality (Wells Q53 and Q56, water quality report) weighted average leaching requirement will be 25% at average. For the purpose of estimating the gross water requirement for each crop, irrigation efficiency (Ei) of 80% was assumed for good irrigation system management. Since leaching fraction more than 10% then gross irrigation is calculated using the following equation: Gross Irrigation = 0.9 Net Irrigation (1- LR)(Ei/100) The (0.9) in the above equation is included to account for the unavoidable deep percolation losses which normally will satisfy approximately 10% of the leaching need. Table (7) shows the gross irrigation water demand for the proposed calculated crops. Table (7): Gross Irrigation Water Demand of Crops (m 3 /dunum). Crop Net Irrigation Gross Irrigation Citrus 760.0 1140 Olives 418.6 627.9 Fruits 512.0 768.0 Alfalfa 1084.3 1626.5 Grains 535.2 802.8 Vegetables 902.0 1353.0 11
9. Reuse Scenarios In general, the components of the irrigation demands include: crop evapotranspiration, irrigation efficiency, leaching requirement, and irrigation losses in the irrigation system. In this study, crop water demand was estimated using crops actual evapotranspiration, 80% on farm irrigation efficiency, and 25% leaching fraction. Leaching requirements were calculated for each crop, along with its suitable on farm management based on the cropping pattern design and the time of application. It is necessary to know how much water a crop will use, not only over the entire growing season, but also during the part of the season when water use is at its peak, - the rate of water use during peak consumptive period- which is the basis for determining the rate at which irrigation water must delivered to the field. Figure 4 indicates that citrus, olive, fruit trees and alfalfa have continued demand pattern with a summer peak 5.06 mm/day, 3.13 mm/day, 3.90 mm/day and 7.78 mm/day during the month of August, respectively. While for vegetable and grain crops peak demands occur during the months of June and May being 6.45 mm/day and 7.15 mm/day, respectively. For cropping pattern selection flexibility and based on crops water requirements during the peak period, an equivalent area for the different crops in the cropping pattern was estimated based on one dunum of a certain crop, as illustrated in Table (8). Table (8): Equivalent area for the different crops in the cropping pattern calculated based on one dunum of a certain crop, according to crop water requirement. Crop Citrus Olives Fruits Alfalfa Grains Vegetables Citrus 1.00 0.55 0.67 1.43 0.70 1.19 Olives 1.82 1.00 1.22 2.59 1.28 2.15 Fruits 1.48 0.82 1.00 2.12 1.05 1.76 Alfalfa 0.70 0.39 0.47 1.00 0.49 0.83 Grains 1.42 0.78 0.96 2.03 1.00 1.69 Vegetables 0.84 0.46 0.57 1.20 0.59 1.00 The selection from this table is started from the top row to the left column of crops. For example, if citrus area increased by 100 dunum, olives area should be reduced by 182 dunum, or to reduce fruit trees area by 148 dunum, or to reduce alfalfa area by 70 dunum, or to reduce grains area by 142 dunum, or vegetables area by 84 dunum, and so on. 12
Monthly Water Requirement (mm) 200.0 180.0 160.0 140.0 120.0 100.0 80.0 60.0 40.0 20.0 0.0 Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Citrus 12.1 17.2 35.0 67.0 89.8 98.8 115.6 117.6 92.2 68.2 38.8 7.7 Olives 1.3 4.8 8.5 35.5 53.3 60.5 72.9 74.6 54.8 37.2 15.2 0.0 Fruit 0.6 1.4 12.8 40.5 60.9 71.6 88.6 91.8 69.8 49.6 24.2 0.2 Alfalfa 40.7 11.0 29.8 60.7 87.9 115.0 154.8 180.8 157.1 122.3 80.8 43.4 Vegetables 8.2 16.8 56.1 111.2 140.0 145.1 132.3 77.1 67.4 80.8 57.1 9.9 Grains 48.5 19.4 10.1 108.2 166.3 123.0 6.1 0.0 0.0 0.0 13.6 40.0 Citrus Olives Fruit Alfalfa Vegetables Grains Figure (4): Mean monthly crop water demand (mm) for citrus, olives, fruit trees, alfalfa, vegetables and grains crops. 13
Based on comprehensive analysis considering the criteria used for crop selection and to balancing water demand all over the year, Three scenarios were investigated and discussed in this report using the recommended cropping pattern, which are citrus 30%, olives 25%, fruit trees 15%, alfalfa 15% and grains 15% for scenarios I and II and citrus 30%, olives 25%, fruit trees 15%, alfalfa 10%, grains 10% and vegetables 10% in scenario III. At the same time, data in table 7 can be used to select any cropping pattern without affecting yearly water requirement demand and/or yearly water recovered. Adjustment of operating hours (pumping) may be needed in some cases but will remain in the range of 10 hours or less in winter months and 12 hours or less in the summer months. Scenario I: On this Scenario it is more advisable to cultivate orchards on the available area to the west of the project along Al Karama Road far away from the political boarder. The profiles of the soils on the area are deep enough to cultivate tree crops. Based on crops water requirements, the available reclaimed water (16,500 m 3 daily) is just enough to irrigate 5375 dunum divided into citrus (1613 dunum), olives (1344 dunum), fruit trees (806 dunum), alfalfa (806 dunum) and grains (806 dunum). Scenario II: It is proposed that on the time when using Scenario II the wastewater will be treated more effectively and consequently the effluent will be of better quality in general. Consequently, the quantity of effluent diverted to the infiltration basin will increase to approximately 23,100 m3 daily. This reclaimed water will be used to irrigate addition land being 7525 dunum in total. The citrus area will increase to 2258 dunum, whereas, olives to 1881 dunum, fruits to 1129 dunum, alfalfa to 1129 dunum and grains to 1129 dunum. Scenario III: Assuming that the planned WWTP in East of Jabalia will work with its full capacity on year 2025. The produced effluent must be totally infiltrated through the infiltration basins. The quality of reclaimed water (39,160m 3 /day which equal 35,600 plus 10% extra) is expected for unrestricted use (Table 9). The quantity of reclaimed water will be enough to irrigation about 12,577 dunum. The citrus area will increase to 3773 dunum, whereas, olives to 3144 dunum, fruit trees to 1887 dunum, and alfalfa and grains each will increase to 1258 dunum. At this scenario vegetable crops will be introduced with an area of 1258 dunum (Table 10), as it is difficult to convince the farmers to accept the recovered water for cultivation of vegetables at the beginning of project. Planting tree crops adjacent to the political boarder should be avoided as much as possible due to the specific political issues in the region. By using the reclaimed water, more irrigation wells on the area will be closed and consequently the original groundwater will be increased and improved through yearly addition of rain water (Figure 5). 14
A B C Scenario I II III Area A A+B A+B+C Figure (5): Map for Different Scenarios. 15
Table (9): Criteria Recommended by PWA for Effluent Standards (PS742, 2003) Criteria Restricted Use 1 Unrestricted Use 2 BOD (Mg/l) 30 20 TSS (Mg/l) 50 30 Total-N (Mg/l) 10-15 10-15 F. coliforms Less than 1000 Less than 200 Helminthes eggs Less than 1 Less than 1 Intestinal nematode Less than 1 ova per liter Less than 0.1 ova per liter Notes: 1. Restricted crops: Cereal crops, industrial crops, fodder crops, crops normally eaten cooked and trees, etc. 2. Unrestricted crops: Crops normally eaten uncooked (vegetables), Sport fields, and parks. Table (10): Areas of Crops (dunum) Irrigated at the Three Scenarios. Crop Scenario I (16,500m 3 /day) Scenario II (23,100m 3 /day) Scenario III (39,160m 3 /day) % Area (dunum) % Area (dunum) % Area (dunum) Citrus 30 1613 30 2258 30 3773 Olives 25 1344 25 1881 25 3144 Fruits 15 806 15 1129 15 1887 Alfalfa 15 806 15 1129 10 1258 Grains 15 806 15 1129 10 1258 Vegetables 0 0 0 0 10 1258 Total area 100 5375 100 7525 100 12577 Total Infiltrated 5,460,000 m 3 7,644,000 m 3 12,958,400 m 3 Total Recovered 6,006,000 m 3 8408400 m 3 14254240 m 3 Balance -546,000 m 3-764,400 m 3-1,295,840 m 3 16
10. Calculation of total water requirements For non-farming activities and may be due to expected climatic change, (15%) is added to the gross irrigation demand for the three scenarios as shown in Tables (11), (12) and (13). Table (11): Water Requirements for Scenario I. Crop % of Area Area (du) Gross Irrigation (m 3 /du) Total Irrigation demand (m 3 /area) Total water requirement (m 3 /area) Citrus 30 1613 1140 1838250 2113988 Olives 25 1344 627.9 843741 970302 Fruit trees 15 806 768 619200 712080 Alfalfa 15 806 1626.5 1311366 1508070 Grains 15 806 802.8 647258 744346 Total 100 5375 5259814 6048786 Table (12): Water Requirements for Scenario II. Crop % of Area Area (du) Gross Irrigation. (m 3 /du) Total Irrigation demand (m 3 /area) Total water requirement (m 3 /area) Citrus 30 2258 1140 2573550 2959583 Olives 25 1881 627.9 1181237 1358422 Fruit trees 15 1129 768 866880 996912 Alfalfa 15 1129 1626.5 1835912 2111299 Grains 15 1129 802.8 906161 1042085 Total 100 7525 7363739 8468300 Table (13): Water Requirements for Scenario III. Crop % of Area Area (du) Gross Irrigation (m 3 /du) Total Irrigation demand (m 3 /area) Total water requirement (m 3 /area) Citrus 30 3773 1140 4301334 4946534 Olives 25 3144 627.9 1974275 2270416 Fruits 15 1887 768 1448870 1666201 Alfalfa 10 1258 1626.5 2045649 2352496 Grains 10 1258 802.8 1009682 1161134 Vegetables 10 1258 1353 1701668 1956918 Total 100 12577 12481478 14353699 17
Since crop water demands varies through out the year with minimum demands in winter months and peak demands occur during summer months, it is recommended to apply leaching requirement during the months of low demands. Such a practice has many advantages in balancing pumping flow rate, effective salt leaching, and preventing the hazardous salts at the peripheral of the wetting front from entering the root zone vicinity. Twenty two percent (22%) of the total leaching requirement should be applied in the month of January, followed by 25% in February, 19% in March, 11% in November, and 23% in December. The average daily irrigation water requirements for each month are given in Table (14). The irrigation demand during the summer months (June, July and August) accounts for about one third of the yearly crops water demands. Thus, in addition to managing timing of leaching requirement application cropping patterns for the three scenarios were designed to optimize and balance pumping flow rate all over the year. The irrigation demand flow rates vary from a minimum of 1083, 1517, and 2738 m 3 /hr to a maximum of 1531, 2149 and 3922 m 3 /hr, with an average of 1541, 2158, and 3687 m 3 /hr for scenarios I, II, and III, respectively (Table 15). Table (14): Net Daily Water Requirements for Irrigation (m 3 /day) Scenario I II III Jan. 12868 18016 28766 Feb. 13122 18371 31144 Mar. 12183 17056 30431 Apr. 12171 17039 29743 May 17073 23902 40541 June 18383 25736 44248 July 17619 24667 43597 Aug. 18495 25893 42673 Sept. 15196 21275 35034 Oct. 10834 15168 26250 Nov. 11432 16005 27377 Dec. 12797 17915 28823 Average 14348 20087 34052 18
The low daily water requirements in the month of July (17619, 24667 and 43597 m 3 ), as compared to that in the months of June (18383, 25736 and 44248m 3 ) for scenarios I, II, and III, respectively, is because grain crops harvested in the month of July and consequently its crop water requirements reduced significantly from 123.0 m 3 /dunum in the month of June to 6.1 m 3 /dunum in the month of July. Also, alfalfa and grain crops cultivated area reduced from 15% in scenarios I and II to 10% in scenario III (In addition to the 10% vegetable crops introduced in scenario III). Table (15): Hourly Water Requirements m 3 /hour Month Scenario I (m 3 /hr) Scenario II (m 3 /hr) Scenario III (m 3 /hr) Jan. 1287 (*) 1802 2877 Feb. 1312 1837 3114 Mar. 1218 1706 3043 Apr. 1217 1704 2974 May 1423 (**) 1992 3378 June 1532 2145 3687 July 1468 2056 3633 Aug. 1541 2158 3556 Sept. 1266 1773 2920 Oct. 1083 1517 2625 Nov. 1143 1601 2738 Dec. 1280 1792 2882 Average 1435 2009 3405 (*) Numbers in white cells calculated based on 10 hours pumping daily in low water demand months. (**) Numbers in shaded cells calculated based on 12 hours pumping daily in high water demand months. 19
11. Recovered Water Table (16) shows the daily recovered water quantities which should be extracted by the recovery wells and pumped through the irrigation networks. The values presented in Table 16 considered the values of Table (14) multiplied by 1.15 (15% extra) to account for non-farming activities and potential climatic change. Table (17) shows the hourly recovered water in each month. Table (16): Daily Recovered (m 3 /day) Scenario I II III Recovered 16500m 3 23100m 3 39160m 3 Jan. 14799 20718 33081 Feb. 15091 21127 35816 Mar. 14010 19614 34995 Apr. 13997 19595 34204 May 19634 27488 46622 June 21140 29596 50885 July 20262 28367 50136 Aug. 21269 29777 49073 Sept. 17476 24466 40290 Oct. 12459 17443 30187 Nov. 13147 18406 31484 Dec. 14716 20602 33146 Average 16500 23100 39160 20
Table (17): Water recovered m 3 per hour Month Scenario I (m 3 /hr) Scenario II (m 3 /hr) Scenario III (m 3 /hr) Jan. 1480 (*) 2072 3308 Feb. 1509 2113 3582 Mar. 1401 1961 3500 Apr. 1400 1960 3420 May 1636 (**) 2291 3885 June 1762 2466 4240 July 1689 2364 4178 Aug. 1772 2481 4089 Sept. 1456 2039 3357 Oct. 1246 1744 3019 Nov. 1315 1841 3148 Dec. 1472 2060 3315 Average 1650 2310 3916 (*) Numbers in white cells calculated based on 10 hours pumping daily in low water demand months. (**) Numbers in shaded cells calculated based on 12 hours pumping daily in high water demand months. 21
An alternate recommendation for maintaining the pump operating at its design capacity throughout the year, pumping hours should be adjusted monthly, with maximum 12 hours operating in the month of June (Table 18). Table (18): Pumping hours for scenarios I, II and III, with the pump operates at its design capacity. Month Scenario I with 1623 m 3 /hr pumping rate Scenario II with 2282 m 3 /hr pumping rate Scenario III with 4163 m 3 /hr pumping rate Jan. 10 10 8 Feb. 10 10 8 Mar. 10 10 8 Apr. 10 10 10 May 11 11 11 June 12 12 12 July 11 11 12 Aug. 12 12 12 Sept. 12 12 11 Oct. 9 8 9 Nov. 9 9 8 Dec. 10 10 8 Average 10 10 10 Figures (6), (7) and (8) show the crop water requirements demand pattern (m 3 /day) for the three scenarios. 22
Figure (6): Crop Water Requirements (m 3 /day) for Scenario I. Figure (7): Crop Water Requirements (m 3 /day) for Scenario II 23
Figure (8): Crop Water Requirements (m 3 /day) for Scenario III 24
12. Irrigation schedule Based on the calculation of the irrigation scheduling in Annex 3 which considered the field water holding capacity obtained from the soil test results, the total area is divided into 6 equal main plots (A1+A2, B1+B2, C1+C2, D, E, and F) (Figure 9). Table (19) illustrates the area of each plot. Table (19): Area of plots. (m 2 ). Plot A=A1+A2 B=B1+B2 C=C1+C2 D E F Area (m 2 ) 2551 2542 2706 2615 2607 2734 Figure (9): Project Area Divided into 6 Main Plots 25
Two plots can be irrigated in one day such as A1 and A2 at the same time to take into account the farthest plot and the most near plot at the same time so the pumping will be equal in every day for each two sub area (Table 19). Table (19): Pumping Schedule Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Sat A1+ A2 B1+ B2 C1+ C2 D E F A1+ A2 Sun B1+ B2 C1+ C2 D E F A1+ A2 B1+ B2 Mon C1+ C2 D E F A1+ A2 B1+ B2 C1+ C2 Tue D E F A1+ A2 B1+ B2 C1+ C2 D Wed E F A1+ A2 B1+ B2 C1+ C2 D E Thu F A1+ A2 B1+ B2 C1+ C2 D E F Fri A1+ A2 B1+ B2 C1+ C2 D E F A1+ A2 26
13. Irrigation methods: The type of irrigation method selected depends on: 1. Crop type, 2. Soil characteristics, 3. Investment costs of system. 4. Ability of farmers to manage the system. The common method of irrigation used actually by farmers in the Gaza Strip is surface irrigation which involves complete coverage of soil surface around the tree (small basin) with water. In the recent years using of more efficient irrigation method, like drip irrigation which is relatively expensive, has increased particularly for high price vegetables. The most appropriate efficient methods to be recommended under our conditions are sprinkler and localized irrigation system, which includes bubbler and drippers. 1. Sprinkler systems: Applying of irrigation water in the form of a spray reaching the soil as rain. There are a variety of sprinkler systems including mini-sprinkler (30-80 l per hr.) which is used actually for irrigation of most citrus, olive and fruit trees. Macro-sprinklers can be used to irrigate cereals, fodder crops and industrial crops. Efficiency ranges from 70 to 80%. 2. Localized systems: Water is applied more efficiently in the vicinity of the plant root zone, so that only the root zone gets wet and avoiding overlapping problems. These systems have low energy requirements (1-3 bar) but require high quality of irrigation water in order to prevent clogging problems. Thus good filtration (90-120 mesh screen or disc filter) unit is required. 2.1. Drip (Trickle) irrigation: Applying water (4-8 l per hr.) continuously through drippers to each individual plant at limited rates. Its efficiency is high (up to 90%) and used for high value crops (vegetables and citrus). Drip irrigation requires clean water without any particles or algae on it. Hazard categories include sand grains, precipitation of carbonates and algae. 2.2. Bubbler irrigation: This system is more recommended as irrigation method for reclaimed water because exit openings are wider than of a dripper and thus less clogging problems. It can be used to irrigate citrus trees under our conditions. The irrigation efficiency is slightly lower than drip irrigation. 3. Sub-surface drip irrigation (SDI): This system is still not enough evaluated through trials under Gaza conditions. Appropriate irrigation systems for proposed crops: Citrus and fruit trees: bubblers, drippers and mini-sprinklers. Fodder and grains: macro-sprinklers Vegetables and row crops: In-line drippers The rate of irrigation can be controlled accurately and nutrients can be also added with irrigation water (fertigation). 27
Annexes Annex 1: Crop tolerance and yield potential of selected crops as influenced by irrigation water salinity (ECw) and soil salinity (ECe) YIELD POTENTIAL2 FIELD CROPS 100% 90% 75% 50% ECe ECw ECe ECw ECe ECw ECe ECw ECe 0% maximum 3 Barley (Hordeum vulgare)4 8.0 5.3 10 6.7 13 8.7 18 12 28 19 Wheat (Triticum aestivum)4,6 6.0 4.0 7.4 4.9 9.5 6.3 13 8.7 20 13 Cowpea (Vigna unguiculata) 4.9 3.3 5.7 3.8 7.0 4.7 9.1 6.0 13 8.8 Sugarcane 1.7 1.1 3.4 2.3 5.9 4.0 10 6.8 19 12 Corn (maize) (Zea mays) 1.7 1.1 2.5 1.7 3.8 2.5 5.9 3.9 10 6.7 Bean (Phaseolus vulgaris) 1.0 0.7 1.5 1.0 2.3 1.5 3.6 2.4 6.3 4.2 VEGETABLE CROPS Broccoli 2.8 1.9 3.9 2.6 5.5 3.7 8.2 5.5 14 9.1 Tomato 2.5 1.7 3.5 2.3 5.0 3.4 7.6 5.0 13 8.4 Cucumber (Cucumis sativus) 2.5 1.7 3.3 2.2 4.4 2.9 6.3 4.2 10 6.8 Spinach (Spinacia oleracea) 2.0 1.3 3.3 2.2 5.3 3.5 8.6 5.7 15 10 Cabbage (Brassica oleracea 1.8 1.2 2.8 1.9 4.4 2.9 7.0 4.6 12 8.1 capitata) Potato (Solanum tuberosum) 1.7 1.1 2.5 1.7 3.8 2.5 5.9 3.9 10 6.7 Corn, sweet (maize) (Zea 1.7 1.1 2.5 1.7 3.8 2.5 5.9 3.9 10 6.7 mays) Sweet potato (Ipomoea batatas) 1.5 1.0 2.4 1.6 3.8 2.5 6.0 4.0 11 7.1 Pepper (Capsicum annuum) 1.5 1.0 2.2 1.5 3.3 2.2 5.1 3.4 8.6 5.8 Lettuce (Lactuca sativa) 1.3 0.9 2.1 1.4 3.2 2.1 5.1 3.4 9.0 6.0 Carrot (Daucus carota) 1.0 0.7 1.7 1.1 2.8 1.9 4.6 3.0 8.1 5.4 Bean (Phaseolus vulgaris) 1.0 0.7 1.5 1.0 2.3 1.5 3.6 2.4 6.3 4.2 Alfalfa (Medicago sativa) 2.0 1.3 3.4 2.2 5.4 3.6 8.8 5.9 16 10 Corn (forage) (maize) (Zea mays) ECw 1.8 1.2 3.2 2.1 5.2 3.5 8.6 5.7 15 10 FRUIT CROPS10 Date palm 4.0 2.7 6.8 4.5 11 7.3 18 12 32 21 Grapefruit (Citrus paradisi)11 1.8 1.2 2.4 1.6 3.4 2.2 4.9 3.3 8.0 5.4 Orange (Citrus sinensis) 1.7 1.1 2.3 1.6 3.3 2.2 4.8 3.2 8.0 5.3 28
Peach (Prunus persica) 1.7 1.1 2.2 1.5 2.9 1.9 4.1 2.7 6.5 4.3 Apricot (Prunus armeniaca)11 1.6 1.1 2.0 1.3 2.6 1.8 3.7 2.5 5.8 3.8 Grape (Vitus sp.)11 1.5 1.0 2.5 1.7 4.1 2.7 6.7 4.5 12 7.9 Almond (Prunus dulcis)11 1.5 1.0 2.0 1.4 2.8 1.9 4.1 2.8 6.8 4.5 1 Adapted from Maas and Hoffman (1977) and Maas (1984). 2 ECe means average root zone salinity of the saturation extract of the soil, (ds/m) at 25 C. ECw means electrical conductivity of the irrigation water in (ds/m). Source: FAO irrigation and Drainage paper No. 29 (Ayers and Westcott, 1976). 3 The zero yield potential or maximum ECe indicates the theoretical soil salinity (ECe) atwhich crop growth ceases. 4 Tolerance evaluation is based on tree growth and not on yield. 29
Annex 2: Guidelines for interpretation of water quality for irrigation (FAO 1985) Potential irrigation problem Units Degree of restriction on use None Slight to moderate Severe Salinity 1 EC w ds/m <0.7 0.7-3.0 >3.0 or TDS mg/l <450 450-2000 >2000 Infiltration SAR 2 =0-3 and EC w >0.7 0.7-0.2 <0.2 3-6 >1.2 1.2-0.3 <0.3 6-12 >1.9 1.9-0.5 <0.5 12-20 >2.9 2.9-1.3 <1.3 20-40 >5.0 5.0-2.9 <2.9 Specific ion toxicity Sodium (Na) Surface irrigation SAR <3 3-9 >9 Sprinkler irrigation me/l <3 >3 Chloride (CL) Surface irrigation me/l <4 4-10 >10 Sprinkler irrigation m 3 /l <3 >3 Boron (B) mg/l <0.7 0.7-3.0 >3.0 Miscellaneous effects Nitrogen (NO 3 -N) 3 mg/l <5 5-30 >30 Bicarbonate (HCO 3 ) me/l <1.5 1.5-8.5 >8.5 ph Normal range 6.5-8.4 1 EC w means electrical conductivity in decisiemens per metre at 25 C 2 SAR means sodium adsorption ratio NO 3 -N means nitrate nitrogen reported in terms of elemental nitrogen 30
Annex 3: Computation of Irrigation scheduling The following calculation is made for Alfalfa. The parameters used for calculation are collected based on the soil investigations carried out by the consultant. FC = 18 %, WP = FC / 1.85 = 9.7 %, Sa = FC WP Sa = 18-9.7 = 8.3 %; Bulk density = 1.4 g/cm 3 ; Sa (mm/m) = 8.3 x 1.4 x 10 = 116.2 mm/m depth Net depth of irrigation dose (d) (mm) = (Sa p) D, Where: Sa: is the available water in mm/m depth. p: is the permissible depletion (fraction), and the recommended p values are: 0.40 0.60 = 0.5 for deep rooted field crops and mature trees. D: is the root depth (m). Location* FC % (w/w) WP = FC/1.85 Available Water = FC-WP mm water/m Depth Net Irrig. Depth (50%) Irrig. Interval WH 15 6.4 3.5 2.9 40.6 20.3 3 days WH 14 10.7 5.8 4.9 68.6 34.3 5 days WH 1 11.7 WH 2 12.9 7 5.9 82.6 41.3 6 days WH 3 17.3 9.3 8 112 56 8 days WH 17 17.5 WH 5 19.6 WH 10 18.4 9.9 8.5 119 59.5 8 days WH 13 22.8 WH 19 22.4 WH 7 22.5 WH 4 23.1 WH 18 23.8 12.8 11 154 77 11 days WH 11 23.8 31
WH 9 25.1 WH 12 25.1 13.6 11.5 161 80.5 12 days WH 6 25.9 WH 16 31.5 17 14.5 203 101.5 14 day * The location of testing FC and presented in the soil report 32