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Irrigation and drainage
Evolution of irrigation development
A global figure for irrigation potential is not available. In 2004, the total water management area was estimated at 679 650 ha, an increase of around 41 percent compared with 1994 (Table 4). Three main types of water management exist:
- Full/partial control irrigation: this concerns an area of 454 310 ha (2004), all irrigated from groundwater, of which 420 386 ha from tube wells and 33 924 ha from spring water. In general, the area irrigated from wells has decreased as many wells have gone out of production due to declining water tables.
- Spate irrigation: the area actually irrigated by spate water varies considerably from year to year, depending on the availability of spate water. It is estimated that the area equipped for spate irrigation (command area) may be as large as 217 541 ha, which was the area also actually irrigated in 2001 (Al-Asbahi, 2001), while in 2002 only 124 683 ha were actually irrigated and in 2004 only 89 363 ha. The government constructed many spate water diversion and canal control structures in some of the main wadis, such as wadi Zabid, Tuban, Abyan, Mowr, Seham and Bayhan. Moreover, spate irrigation structures have been maintained and improved for enhancing spate water management and distribution along these wadis. The Irrigation Improvement Project (IIP) has been established recently to introduce the participatory spate irrigation management approach on two pilot wadis (Zabid and Tuban). This project created ‘water user associations’ (WUAs) to manage the spate structures on the wadis and to take over the operation and maintenance of the spate structures. The project also created the Water Council (WC) from the members of those associations and the local authorities.
- Small-scale irrigation: 347 dams were recently constructed in the different governorates especially in the uplands to capture rainwater for complementary irrigation purposes in inland valleys. Moreover, 519 small reservoirs and water cisterns have been constructed in different upland villages. The main purpose of these water harvesting or small-scale irrigation schemes is to use the water for complementary irrigation. The total area irrigated by these systems was about 7 799 ha in 2004, including 4 215 ha from dams. It increased to 8 526 ha in 2005 thanks to the construction of new dams.
Irrigation efficiency is low, between 35 and 45 percent depending on field levelling and the water conveyance system used. Localized irrigation systems (drip and bubbler) are introduced through several projects on limited demonstration areas and 485 ha have been realized up to now. Because of the high cost of sprinkler irrigation systems, they have been installed in very limited areas only, such as the governmental farms and the big investment farms mostly used for fodder crop production. To enhance water conveyance and distribution efficiency, the government introduced PVC buried pipes and GI pipes to the farmers to replace the earthen distribution canals and offered subsidies reaching 50 percent of the equipment costs. It is estimated that irrigation efficiency could be increased to 60 percent by installing the conveyance pipe system and to over 80 percent by adopting localized irrigation systems. Average yields of crops growing under the improved conveyance pipe system and localized irrigation systems are assumed to increase by 5 percent and 10 percent respectively. In 2004, 99.9 percent was surface irrigation and 0.1 percent was localized irrigation (Figure 3).
Role of irrigation in agricultural production, the economy and society
The price of irrigation equipment has increased considerably in recent years. The average cost of a surface irrigation system with a piped conveyance and distribution system is about US$800/ha. The cost of a localized irrigation system depends on the type: the estimated cost of a drip irrigation system for fruit trees is about US$2 600/ha and for vegetables about US$3 600/ha, while a bubbler irrigation system costs about US$3 000/ha. A central pivot sprinkler system is estimated to cost about US$6 000–8 000/ha. The cost of the operation and maintenance is approximately US$120/ha for the piped surface irrigation system and US$300/ha for a localized irrigation system. The farmers are responsible for operation and maintenance costs.
Government action focuses on the construction of water harvesting schemes and spate irrigation structures with the participation of the beneficiaries, as well as on the rehabilitation of those structures. The beneficiaries are responsible for operation and maintenance. The cost of small and medium spate diversion works and water harvesting structures is between US$1 500 and 2 000/ha.
The crops grown under full/partial control irrigation can be aggregated into six types: cereals, fruits, vegetables, cash crops, pulses and fodders. In 2004, the total harvested irrigated cropped area was 527 038 ha distributed as follows (Figure 4):
- cash crops: 157 878 ha or 30 percent, including 99 504 ha of qat; other cash crops are cotton, coffee, tobacco and sesame;
- cereals: 123 195 ha or 23 percent, mainly sorghum and wheat and to a lesser extent maize, barley and millet;
- fruit trees: 75 997 ha or 15 percent, of which 11 percent is banana and 15 percent citrus; other crops under this category are grapes, palm dates, papaya, apricots, peach, quince, figs, apples and guava;
- vegetables: 72 364 ha or 14 percent, including 16 870 ha of potatoes cultivated particularly in the Dhamar and Amran governorates;
- fodder: 70 772 ha or 13 percent;
- pulses: 26 832 ha or 5 percent; most pulses are rainfed.