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Occupied Palestinian Territory
Irrigation and drainage
Evolution of irrigation development
There are 80 000 ha suitable for irrigation in the Occupied Palestinian Territory of which 61 000 ha in the West Bank and 19 000 ha in the Gaza Strip. In 2003, about 24 000 ha of this land were irrigated, of which 12 600 ha in the West Bank and 11 400 ha in the Gaza Strip (Table 9 and Table 10).
Table 11 shows the distribution of irrigation technologies in the semi-coastal zone which is typical when irrigation water sources come from irrigation wells. In general drip and trickle irrigation systems are used to irrigate vegetables in the coastal, semi-coastal and the Ghor areas. A small percentage of vegetables are still irrigated by traditional methods as well as most citrus trees.
There are still a few earth canals used in certain areas of the West Bank, such as the El-Faria and Bethan springs (producing about 10 million m3/year) and parts of Auja (producing about 12 million m3/year on average). In these areas, water is distributed with no charge to the farmer and the sizes of farms are usually small which increases the number of farmers sharing such sources. These canals require high maintenance costs due to weed growth and land slides in hilly areas. They also suffer from high deep-percolation and evaporation losses. Concrete canals are also used, especially in the Jericho area and parts of Auja, to convey and distribute water from natural springs to farms. The conveyance efficiency is high in such canals when they are maintained with good linings. Any losses are due to evaporation. Farmers usually use plastic lined pools to store their shares of fresh spring water and mix them with brackish well water. Then water is pumped and applied through trickle irrigation systems. From nearly all wells in the Occupied Palestinian Territory water is pumped into steel pipes which convey the water to the irrigation systems directly in the farms. This includes the coastal, the semi coastal and large parts of the Ghor and semi-Ghor zones. As the pumping costs are high, the cost per unit water is high and thus farmers need to use better distribution and conveyance efficiencies through the use of pipes. Furthermore, most farms irrigated by wells use pressurized irrigation systems, so farmers have to use the pressure head applied by the turbine pumps at the well to supply their irrigation systems with the needed pressure.
Surface irrigation systems are used either in areas irrigated by natural springs (Faria, Bethan, Nassarieh and Aqrabanieh) or for irrigating citrus trees, using basins or furrows. Basin irrigation is used mostly for irrigating trees, mainly citrus. For every tree, a small basin is constructed and water is distributed to the basins through small earth ditches and in some case using polyethylene pipes. Furrows of a helical type to minimize tail water runoff are still used to irrigate vegetables in some areas irrigated by natural springs. Application efficiency of surface irrigation systems rarely reaches 60 percent.
Solid set sprinklers are usually used to irrigate potatoes, onions, carrots, radishes and spinach. These sprinklers are often used to supply the water needed for land preparation in greenhouses and to supply water to cabbages at certain growth stages. The cost of solid set sprinklers is about US$4 000/ha including sprinklers, polyethylene pipes, fittings and valves.
Micro sprinklers are also used to irrigate fruit trees, especially citrus trees. Two sprinklers are usually installed per tree. The cost of these systems depends on the density of the sprinklers in the farm and the type of cropping (trees or densely planted vegetables). For trees, the cost of these systems is about US$3 500/ha. Application efficiency of sprinkler irrigation systems can reach 85 percent. However, due to poor design and operation of such systems the efficiency is usually less. Due to the inflexibility of water supplies, farmers sometimes tend to operate such systems for several hours. This results in application rates that are higher than the infiltration capacity of soil. Therefore, water is lost in the form of surface runoff which causes soil erosion and loss of nutrients. Most vegetable crops are irrigated using trickle irrigation.
Role of irrigation in agricultural production, the economy and society
Open field vegetables are grown in the five agro-climatic zones. Common crops include tomatoes, cucumbers, eggplants and squashes. The timing for planting each type of vegetables is site dependent. For the Ghor area, they are either planted in late summer/early fall (August-October), or in late winter/early spring (January-February). Vegetables are not usually planted during summer months in the Ghor area due to the high temperatures there. In other climatic zones, most vegetables are usually planted during most of the year except winter. Frost spills are a major concern for farmers growing open field vegetables especially during late fall or early spring. Frost is possible in all climatic zones, although it is rare in the Ghor. Open field vegetables cover more than 8 900 ha or 70 percent of the total area of vegetables in the Occupied Palestinian Territory (Table 12 and Figure 6). The percentage is higher in the Ghor area than other areas due to the lower possibility of frost in that area. Productivity of open field vegetables depends on the type of vegetables and ranges from about 7 tonnes/ha for green beans to about 70 tonnes/ha for tomatoes. On average, productivity is about 25.7 tonnes/ha for open field vegetables.
Low plastic tunnels provide some protection from frost for vegetables. However, they are less efficient than plastic houses. Farmers tend to use these tunnels especially in the Ghor area to provide protection against frost and improve the agricultural microclimate. Productivity in these tunnels is usually higher than that in open field agriculture and less than that in greenhouses. Low plastic tunnels cover about 2 000 ha with a productivity of 28.3 tonnes/ha.
Plastic houses allow good control of the climate, thus allowing vegetables to be planted all year in most areas in the Occupied Palestinian Territory, but they are mostly used in the coastal and semi-coastal zones. This could be attributed to the availability of irrigation water in these zones and to the warm winter climate with low possibility of frost (but not as warm as the Ghor where production is possible in open field conditions during winter). New vegetable varieties have been introduced which are suitable for the area and have high productivity. On average, productivity in plastic houses is about 95 tons/ha, but will be much higher for certain crops such as cucumbers and tomatoes where productivity is 150 tons/ha or more. Plastic houses cover more than 1 800 ha. This area has been continuously increasing over time.
Field crops include potatoes and onions in addition to forages and grain crops. Field crops cover about 2 800 ha with a productivity of 20.7 tonnes/ha. This high average is attributed to the large areas of potatoes and onions and the low areas of forages and grain crops. Grain crops such as wheat and barley are rarely planted under irrigated agricultural conditions with the exception of the Ghor area, where rainfall is not sufficient for planting grain field crops which are frequently planted as part of crop rotation. In areas irrigated by springs, farmers plant some field crops such as wheat, barley and alfalfa as part of their crop rotation.
Irrigated fruit trees planted in the Occupied Palestinian Territory are mainly citrus trees in the coastal and semi-coastal areas and bananas in the Ghor. In the coastal zone, the area of citrus trees was reduced from about 7 000 ha in the early 1990s to about 4 300 ha in 1996/1997. Many of these citrus trees are in poor condition and lack proper maintenance and enough water due to the low availability of water, the low quality of irrigation water and the possible loss of these lands to urbanization as a result of high land prices there. In the semi-coastal areas, the conditions of citrus farms are better than those in the Gaza Strip due to better water availability and quality. Citrus trees cover about 1 400 ha in this zone with a productivity of about 35 tonnes/ha. There are about 280 ha of citrus trees located within the El-Faria wadi which is located within two agroclimatic zones (Ghor and semi Ghor). Jericho district has about 140 ha of citrus trees which depend mainly on spring water. However, the dominant fruit trees in Jericho are bananas covering 580 ha. Although bananas consume more water than citrus trees, they sell at higher prices in the local markets, making their plantation economically feasible in the Ghor.