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Irrigation and drainage
Evolution of irrigation development
The history of irrigated agriculture in Afghanistan goes back more than 4 500 years to an ancient settlement near Kandahar (ICARDA, 2002).
By 1978, the surface water potential was more or less fully exploited by existing irrigation systems, if no further regulation works were constructed, although the efficiency of exploitation left room for considerable improvement. Irrigated areas could have been expanded by building major dams and other water regulation structures, all of which required major capital investment. There is no estimate, even rough, of irrigation potential.
For the past 30 years, the rural sector has been severely impacted by war and civil unrest. Irrigation system structures have been damaged, sometimes deliberately. While many rehabilitation efforts have necessarily been emergency assistance, long-term strategies to improve the performance and reliability of irrigation systems are also required (Rout, 2008). An estimated 27 to 36 percent of all irrigation systems were directly affected by war before 2000. These figures do not take into account the indirect effects of neglect and abandonment.
Irrigated land is usually located in the river basins of the north, west and southwest (ICARDA, 2002). Almost 75 percent is located in the northern and Helmand river basins. A FAO satellite survey, conducted in 1993, Table 6 lists irrigated land cover by river basin. It shows total irrigated area as 3.21 million ha, of which 48 percent is intensively cultivated and 52 percent intermittently with one or more crops each year. It is assumed that the survey covers both informal and formal irrigation systems (Table 7).
Not listed, however, is the area used for private gardens, vineyards and fruit trees, which could be over 90 000 ha and could receive some form of irrigation (Rout, 2008). It is estimated that in 2002 the area was the same, area actually irrigated was 1.73 million ha, or 54 percent of the area equipped for irrigation. In 2011, the area actually irrigated was an estimated 1 896 000 ha.
In 1967, a survey estimated the total irrigation area to be 2.72 million ha. The survey shows the existence of nearly 29 000 systems, of which 27 percent drew from surface water sources (rivers and streams), and the remainder from groundwater sources (springs, karez and wells) (Rout, 2008). While surface water systems made up less than one-third of the total number, they covered 86.5 percent of the irrigated area, confirming the importance of surface water as the main irrigation water source. Springs account for 6.9 percent of the area, karezes for 6.2 percent and shallow and deep wells for 0.4 percent (Favre and Kamal, 2004). In 2002 it was estimated that 18 percent of the total area equipped for irrigation on 3.21 million ha and 16 percent of actually irrigated area on1.73 million ha were irrigated using groundwater (Figure 3).
In 1963, some 114 000 ha were reported to be equipped for sprinkler irrigation.
Irrigation systems can be divided into two main categories: informal irrigation systems (surface water systems, karez, springs and wells) and formal irrigation systems.
Informal systems are centuries-old and traditionally developed and managed by local communities within the constraints of local resources. They have undergone social and physical changes, and expand or contract based on water availability or challenges arising from years of conflict. Informal systems account for 88 percent of the country’s irrigated area (Rout, 2008). They are divided into four categories:
- Informal surface water systems: They make up 75 percent of the irrigated area. Their prevalence largely results from widespread availability of both water resources from rivers and streams as well as adjacent land suitable for development, usually along river terraces and alluvial plains. The key infrastructure typically found in surface water systems includes: diversion structures (sarband); main, secondary and tertiary canals (predominantly made of unlined earth); control structures (weirs, sehdarak bifurcators, offtakes and spillways); conveyance structures (siphons, aqueducts, super-passages and culverts); protection structures (embankments as well as gabion and retaining walls); and access and ancillary structures (water mills, bridges and access points). Some schemes include small retention dams and water-harvesting structures (Rout, 2008). Small-scale informal surface water systems are the traditional irrigation systems, many of which have been established for centuries. Large-scale informal surface water systems are located mainly on the plains and along the main valleys. Although called informal, their operation and maintenance was highly structured. Large parts of these schemes were abandoned because land became infertile because of waterlogging and salinization, particularly in the Hari Rod, Farah Rud and Helmand valleys.
- Karez (qanat): These date back several millennia. They comprise an unlined underground gallery in the hillside that brings water by free flow from underground aquifers to be used for surface irrigation. Dug by local craftspeople from shafts at close intervals, they are small but may be many kilometres long. Although most are shorter than 5 km, the length of the karez can run up to 16 km; it is said the longest Afghanistani karez is 70 km long. It is estimated that 6 740 kareze still supply water to 168 000 ha, as in 1967, the date of the last inventory. Average irrigated area per karez is 25 ha, but ranges from less than 10 ha to more than 200 ha. It should be noted that kareze are often used for domestic water supply. Karez irrigation is common in the south and southwest of the country and less in the north. Most karez systems are located within the Helmand river basin (Rout, 2008). One of the disadvantages of the karezes is that there is no mechanism to stop water flowing during winter, or when there is no need for irrigation. In each karez about 25 percent of total annual volume of water is wasted (ICARDA, 2002). The karez provides sustained perennial flow and good quality water and has the advantage of being relatively immune to natural disasters (such as earthquakes and floods) and human destruction in war (Tamuri, 2007). However, these systems may commonly face problems such as vulnerability to collapse of subsurface infrastructure, water losses in canals, flood damage and groundwater depletion. Karez are organized and operated by local communities, traditionally under a karezkan specialist responsible for construction and maintenance of subsurface sections; a mirab (water master) oversees surface distribution operations. Water allocations, similar to surface water systems, are based on water entitlements and rotations (Rout, 2008). Most karez are no longer in use (World Bank, 2009).
- Springs: Many rural communities depend on the nearly 5 558 spring-fed systems estimated to irrigate approximately 187 000 ha. The relatively low flow rate of springs means that the systems are often supplemented by diverted surface water flows when available. The systems are commonly found in upper and tributary catchments and are concentrated in the more mountainous central and southeastern provinces (Rout, 2008). When the groundwater level falls such as during drought years, the result is reduced outflow from springs. This is why some of the worst drought-stricken areas of the country are located in regions where farmers depend heavily on spring water for irrigation (ICARDA, 2002).
- Wells: Estimates from the late 1960s indicated that less than 1 percent of the total irrigated area is supplied by water from wells. Groundwater is lifted from large diameter shallow wells with the help of a wheel (arhad), animal power supplies irrigation water to an individual farmer’s fields. The irrigated land does not exceed 3 ha. The total number of shallow wells in Afghanistan is 8 595, which irrigate around 12 000 ha of land. In recent years, however, the use of modern well-drilling and pumping technology has been more widespread, considerably increasing the number of wells and their capacity (ICARDA, 2002; Rout, 2008) (Table 8).
Formal systems are large-scale irrigation schemes that have been developed with central government assistance, financing, management, operation and maintenance. With additional support from bilateral and multilateral donors, most of these schemes were developed between the late 1940s and the 1970s. Afghanistan has ten formal schemes totalling nearly 333 000 ha. The largest is the Helmand-Arghandab scheme (Helmand province). The other systems are: Sardeh (Ghazni), Parwan (Parwan and Kabul), Nangarhar (Nangarhar), Sang-i-Mehr (Badakhshan), Kunduz-Khanabad (Kunduz), Shahrawan (Takhar), Gawargan (Baghlan), Kelagay (Baghlan) and Nahr-i-Shahi (Balkh) (Table 9) (Rout, 2008; Favre and Kamal, 2004).
Most of these schemes are supplied by surface water, and very little is known about the formal irrigation schemes supplied by groundwater from deep and shallow wells. In Khost/Paktia province, surface water irrigation schemes were supplied by some 100 deep wells until the late 1980s (ICARDA, 2002). Several of the schemes have storage dams and capacity to generate hydropower. Over the past 30 years, the schemes have become heavily degraded because of lack of funding and loss of technical and institutional capacity to support operation and maintenance (Rout, 2008). By 1993, only a small part of these schemes was operational. Land tenure was different than most traditional systems in that ownership of land was registered. Some schemes were operated under private land ownership agreements, while others were operated as state farms where land ownership was deeded to the State. Since 2003, a number of ongoing rehabilitation initiatives have been launched (Rout, 2008).
There have been no concerted efforts to exploit water using modern technology, mainly because of the high initial and maintenance costs (ICARDA, 2002).
Small-scale schemes (< 3 ha) account for 83 percent of irrigated farms and 8 percent of rainfed, medium-scale schemes (3-6 ha) account for 14 percent of irrigated farms and 8 percent of rainfed, while large-scale schemes (> 6 ha) account for 3 percent of irrigated farms and 84 percent of rainfed (Qureshi, 2002). The average irrigated farm is 1.4 ha, while the average rainfed farm is 6–7 ha.
Role of irrigation in agricultural production, the economy and society
In 2011, total harvested irrigated cropped area was an estimated 2 176 000 ha. Wheat accounts for 1 303 000 ha, or 59.9 percent of the harvested irrigated copped area, followed by rice 208 000 ha (9.6 percent), maize 183 000 ha (8.4 percent), fruit trees (including grapes) 198 000 ha (9.1 percent), barley 116 000 ha (5.3 percent), vegetables 69 000 ha (3.2 percent), cotton 33 000 ha (1.5 percent) and other crops on 99 000 ha (4.5 percent) (Table 7 and Figure 4).
Sustaining and increasing productivity on irrigated land is essential for the overall food security of Afghanistan.
Cropping intensity varies widely from system-to-system according to the relative scarcity of water in relation to land. It may achieve 200 percent in large, formal systems with full water control (upstream of the river systems, when climatic conditions allow an early wheat crop), while in other systems up to two-thirds of the equipped area are kept fallow each year on a rotation basis.
Per capita wheat consumption in Afghanistan is one of the highest in the world. Pre-war, irrigated land produced 77 percent of all wheat and 85 percent of all food and agricultural crops. Irrigated yields are estimated to be three times that of rainfed yields.
In 1993, the average cost of irrigation scheme rehabilitation was an estimated US$200/ha for small schemes. Rehabilitation costs for large, modern schemes, including main structures, are considerably higher.