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Irrigation and drainage
Evolution of irrigation development
Because of the rainfall and hydrological patterns, the need for irrigation is highest in the central dry zone, while in the delta there is more concern aboutt drainage and flood protection.
It is thus logical that the first irrigation works should have been undertaken near Bagan (Pagan) in the central region in the eleventh and twelfth centuries. They were typically composed of diversion systems on tributaries of the middle Ayeyarwady, and were designed to provide security to the main season rice crop. Storage reservoirs were also constructed for the same purpose. The ancient systems were subsequently modernized, extended and operated in the traditional manner, with a greater emphasis on the upgrading and development of the existing flood protection and drainage facilities in the Ayeyarwady delta. This enabled the development of rice cultivation and made Myanmar a major rice-exporting country before the Second World War. Dam construction and irrigation network implementation were significantly accelerated in the 1960s, 1970s and after 1990. The irrigation potential, considering both water and soil resources, is about 10.5 million ha.
In 1986 the Ye-U irrigation rehabilitation and modernization project was approved. The main objective of the project was to rehabilitate and modernize the Ye-U irrigation and drainage system commanding 49 370 ha in the Mu river basin, located in the central dry zone, mainly to increase the production of rice in the area (World Bank, 1995).
The total area equipped for irrigation in 2004 was an estimated 2 110 000 ha (MOAI, 2010). In 2000 and 1995 was around 1 841 000 ha and 1 555 000 ha respectively.
Irrigated areas were traditionally supplied by water from weirs used to divert rivers or dams and tanks. Since the 1980s, however, there has been substantial development of wells and water is pumped from rivers. Other types of irrigation water supply include windmills, watermills, watering with buckets, ponds, etc. In 2000, out of the total irrigated area of 1 841 000 ha, 31 percent was supplied by canals (57 percent managed by the government and 43 percent by farmers), 11 percent was supplied by tanks (93 percent managed by the government and 7 percent by farmers), 4 percent by tubewells, 46 percent by pumps and 8 percent by other types of irrigation water supply (Fujita and Okamoto, 2006). Water resources for pump lift irrigation are mainly based on the flow of three major rivers, the Ayeyarwady, Chindwin, and Sittaung. Further expansion of electric pumping, however, still remains constrained, owing to limited supply of electricity (MOAI, 2010).
All irrigation in Myanmar is surface irrigation. Sprinkler and localized irrigation have been developed only on pilot farms, and altogether do not exceed 50 ha.
There are two types of irrigation management in Myanmar: public and private schemes. Government schemes account for 53 percent of weir schemes and 81 percent of the dams and tanks (all dams of and above 6.1 m). Wells and pump irrigation, although possibly originally implemented by the services of the former Ministry of Agriculture, are mainly private.
Although farmers are responsible for implementation, management, operation and maintenance of the private schemes, both the Irrigation Department and the Water Resources Utilization Department provide technical and financial assistance.
There are important groundwater aquifers in Myanmar. Their exploitation, however, has been limited to municipal water supply and to the intensive irrigation of vegetables and other high-value crops from hand-dug wells. In the central dry zone, where most of the potential for economical run-of-the-river diversion schemes has been used, dams for surface water irrigation projects, as well as groundwater irrigation projects, were started in the 1980s. Irrigation from groundwater was practised on 55 175 ha in 1995, mainly for cotton, wheat, beans and pulses (Table 4 and Figure 3). Groundwater is drawn using diesel pumps (77 percent of the area), followed by electric pumps (15 percent) and artesian wells (8 percent). Generally, one tubewell allows supplementary irrigation on 4 ha. The groundwater irrigation area increased to 81 000 ha in 2000 and 100 000 ha in 2003 (Irrigation Department, 2004).
In the Myanmar classification of cultivated areas, inland valley bottoms that are equipped for irrigation are generally known as maye land, and, in 1995, were estimated at around 27 000 ha. To generate increased rice production, a combination of rice and fish farming, on plots of 1-2 ha protected by embankments, has been introduced into maye land areas, where rice yields were uncertain. Another type of water management is called kaing land in the Myanmar classification (flood recession cropping). This land, which is mainly in the Ayeyarwady delta are mostly cultivated with vegetables.
Role of irrigation in agricultural production, the economy and society
Jute used to be the second most widely cultivated crop (after rice), but it has now been replaced by cash crops such as beans, pulses, sunflowers, chilies and vegetables. In 2006, total harvested irrigated cropped area was an estimated 2 722 000 ha, of which the most important crops are rice accounting for 1 861 000 ha (68 percent), pulses 284 000 ha (10 percent), wheat 89 000 ha (3 percent), cotton 85 000 ha (3 percent) and sugarcane 79 000 ha (3 percent) (Table 4 and Figure 4).
Rice is currently cultivated on 6.54 million ha (of which 1.25 million ha irrigated), comprising 4.90 million ha in the rainy season and 1.64 million ha in the dry season. Rice is mostly found in the delta and central dry zone areas. Supplemental irrigation is supplied for the rainy season rice cultivation mainly in the Mandalay, Sagaing and Magway regions, which are located in the central dry zone of Myanmar, where the rainfall is insufficient for the crop-water requirement. Other upland crops are cultivated there in the dry season using irrigation.
About 60 percent of the delta region, including the Ayeyarwady, Bago and Yangon region of Lower Myanmar, is cultivated with rainfed rice. Dry season rice is mostly cultivated in Lower Myanmar using irrigation. Rice cultivation has increased from 4.78 million ha in 1988 to 6.54 million ha in 2003, and production from 12.96 million tonnes to 22.79 million tonnes. Rice exports increased to 1 million tonnes in 2004. According to national planning targets, the sown area of rice will be expanded to 7.29 million ha (Naing, 2005).
Among other major upland crops are pulses and oilseeds. Pulses are cultivated for export and the cost of cultivation is relatively inexpensive. As a result of the increasing demand for both domestic consumption and export, the cultivation of pulses has increased from 0.73 million ha in 1988 to 3.31 million ha in 2003, of which 0.28 million ha are irrigated, production has increased from 0.5 million tonnes to 3 million tonnes. Around 1 million tonnes of pulses are now being exported. The major oilseed crops are groundnut, sesame and sunflower and cultivation of these crops increased to 2.78 million ha in 2003 (Naing, 2005).
In 1999, average irrigation development costs varied from US$2 000-8 000/ha (12 300-49 100 kyatts/ha).
Status and evolution of drainage systems
In the Ayeyarwady delta, drainage, salt intrusion and flood protection are major concerns. Embankments have been developed to protect large areas from both floods and salt intrusion. These embankments may have drainage facilities. Around 1995, there were a total of 318 flood protection works, both government (88 percent) and private (12 percent), protecting a total of 1.2 million ha of cultivable land. A small portion of this area (less than 10 percent) is also irrigated by small lift pumps.
In 1995, 193 363 ha were reported as being equipped with surface drainage networks. Drainage works are also considered a form of flood protection. In 1999, drainage and embankment development cost around US$1 200/ha (7 400 kyatts/ha).
Salinization caused by irrigation is mainly found in the central dry zone, near Meiktila in Mandalay Division, where groundwater is used for irrigation.