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Irrigation and drainage
Evolution of irrigation development
The oldest and most deeply rooted hydraulic civilization of the world started in Mesopotamia, from which agricultural and agro-ecological systems developed that are strongly related to the presence of water. The history of irrigation started about 7 500 years ago when the Sumerians built a canal to irrigate wheat and barley in Mesopotamia.
Irrigation potential is estimated at over 5.55 million ha, of which 63 percent in the Tigris Basin, 35 percent in the Euphrates Basin, and 2 percent in the Shatt Al-Arab Basin. Considering the soil resources, it is estimated that about 6 million ha are classified as excellent, good or moderately suitable for flood irrigation. With the development of water storage facilities, the regulated flow has increased and significantly changed the irrigation potential, which was estimated at 4.25 million ha only in 1976. However, irrigation development depends to a large extent on the volume of water released by the upstream countries.
The total managed water area was estimated at 3.5 million ha in 1990, all of it equipped for full or partial control irrigation (Table 4). The areas irrigated by surface water were estimated at 3 305 000 ha, of which 105 000 ha (3 percent) in the Shatt Al-Arab River Basin, 2 200 000 ha (67 percent) in the Tigris River Basin, and 1 000 000 ha (30 percent) in the Euphrates River Basin. However, not all these areas are actually irrigated, since a large part has been abandoned due to waterlogging and salinity. The areas irrigated from groundwater were estimated at 220 000 ha in 1990, with some 18 000 wells (Figure 3). About 8 000 ha were reported to be equipped for localized irrigation, but these techniques were not used. Water use efficiency at the farm level is reported to be poor.
In 1997, the total irrigated area was estimated at 3.4 million ha, of which 87.5 percent obtained water from river diversion, 9.2 percent from rivers using irrigation pumps, 3.1 percent from artesian wells and 1.2 percent from spring sources (FAO, 2003).
In December 1983 the first 87 500 ha stage of the massive Kirkuk Irrigation Project (renamed Saddam) was opened, of which more than 300 000 ha were eventually irrigated. In 1991 a large supplemental irrigation project, the North Al-Jazeera Irrigation Project, was launched in order to serve some 60 000 ha using a linear-move sprinkler irrigation system with water stored by the Mosul Dam (former Saddam Dam). Another irrigation project, the East Al-Jazeera Irrigation Project, involved the installation of irrigation networks on more than 70 000 ha of rainfed land near Mosul. These projects were part of a scheme to irrigate 250 000 ha of the Al-Jazeera plain. To the south of Baghdad, completed land reclamation schemes included Lower Khalis, Diwaniya-Dalmaj, Ishaqi, Dujaila and much of Abu Ghraib. The massive Dujaila project was intended to produce about 22 percent of Iraq’s output of crop and animal products. Consultants have designed irrigation schemes for Kifl-Shinafiya, East Gharraf, Saba Nissan, New Rumaitha, Zubair, Bastora, Greater Musayyib and Makhmour. The project’s main outfall canal, completed in December 1992, is known as the “Third River”. It runs for 565 km from Mahmudiya, south of Baghdad, to Qurnah, north of Basra, and carries saline water to an outlet on the Gulf (Taylor & Francis Group, 2002).
More recently, a new development project on the “Dissemination of improved irrigation technologies” was introduced to increase wheat production. The target was to plant up to 0.5 million ha of wheat under supplemental irrigation by the year 2007. Currently, there are about 3 500 new farms in Mosul Province under supplemental irrigation, with an average size of holding of 25 ha per farm. Wheat is the major winter crop, covering 73 percent of the project area (ESCWA and ICARDA, 2003).
Role of irrigation in agricultural production, the economy and society
During the 1980s the State attempted to foster private sector investment in Iraq’s agriculture. Oil revenues were used to acquire western technology and to lavish government subsidies on the sector. The government distributed high-yielding seeds and invested heavily in the irrigation infrastructure. The 1991 Gulf War resulted in significant damage to the irrigation and transportation infrastructure vital to Iraq’s agricultural sector, but it is difficult to evaluate its extent or severity.
Between 75 and 85 percent of crop area is generally planted to grains (mostly wheat and barley). About one-third of Iraq’s cereal production is produced under rainfed conditions in the foothills of the northwest in Iraqi-Kurdistan. Winter wheat and barley are planted in the fall (September–November) and harvested in the late spring (May–June). Yields on the rainfed crops are generally poor and vary significantly with rainfall amounts. The remaining two-thirds of Iraq’s cereal production occur within the irrigated zone that runs along and between the Tigris and Euphrates rivers.
In 1991, there were 224 490 ha of irrigated wheat, with an average yield of 2.7 tons/ha, while the rainfed wheat area was estimated at 508 620 ha, with an average yield of 1.7 tons/ha. There were 200 770 ha of irrigated barley, with an average yield of 1.8 tons/ha, while the rainfed barley area was estimated at 323 730 ha, with an average yield of 1.3 tons/ha. In 1998 the total area planted with grain crops increased, giving 717 000 ha of irrigated wheat and 785 000 ha of irrigated barley (Figure 4). Other main irrigated crops are rice, maize, vegetables, sunflower, but also date and fruit trees, which are important for the economy of the southern part of the country. For the most part, a single crop is planted per year, although there is some multiple cropping of vegetables where irrigation water is available.
Record cropped areas were achieved in 1992 and again in 1993. However, agricultural productivity suffered from lack of fertilizers, agricultural machinery and the means of spraying planted areas with pesticides. Iraq’s irrigation infrastructure fell into disrepair and salinity spread across much of the irrigated fields of central and southern Iraq. Moreover, a severe drought which persisted throughout much of the Middle East from 1999 through 2001 devastated crop output in Iraq. Cereal production in Iraq’s rain-dependent northern zone was particularly hard hit, but even the irrigated production of the central and southern region suffered from diminished water availability (down to 43 percent of normal levels). As a result of the drought, Iraq’s annual cereal production per capita plummeted from its already low 1999 level of 77 kg to only 39 kg by 2000. Shortage of fodder resulted in forced slaughter of sheep and compounded the impact of an outbreak of foot-and-mouth disease in 1998. An estimated one million head of livestock died due to lack of medicines (Schnepf, 2003).
Status and evolution of drainage systems
Throughout history the irrigated agriculture of Iraq’s central and southern region has been menaced by salinization. Salinity was already recorded as a cause of crop yield reductions some 3 800 years ago. It spread across much of the irrigated fields as the Government ended its maintenance of the irrigation system. The water table of southern Iraq is saline and so close to the surface that it only takes a little injudicious over-irrigation to bring it up to root level and destroy the crop. High groundwater tables affect more than half of the irrigated land. Once severe salinization has occurred in soil, the rehabilitation process may take several years (Schnepf, 2003).
Half of the irrigated areas in central and southern Iraq were found to be degraded due to waterlogging and salinity in 1970. The absence of drainage facilities and, to a lesser extent, the irrigation practices (flooding) were the major causes of these problems. In 1978 a land rehabilitation programme was undertaken, comprising concrete lining for irrigation canals, and installation of field drains and collector drains. By 1989 a total of 700 000 ha had been reclaimed at a cost of around US$2 000/ha. According to more recent estimates 4 percent of the irrigated areas were severely saline, 50 percent medium saline and 20 percent slightly saline. Irrigation with highly saline waters (more than 1 500 ppm) has been practiced for date palm trees since 1977. The use of brackish groundwater is also reported for tomato irrigation in the south of the country.
Due to the relief and the sloping river beds the possibilities of draining the excess irrigation or flood water back to the rivers are few or none. A comprehensive network of sub-surface tile drains and surface drainage canals collects the drainage water from the agricultural fields and eliminates it through the Third River’s main out-fall drain to the Shatt Al-Arab in an attempt to keep the irrigated lands free of salinization and waterlogging problems. Drainage water pumping stations are used to lift the effluent water to the main out-fall and onwards by gravity to the Gulf. Almost all land reclamation and development projects contain both irrigation and drainage components (FAO, 2003).