Since ancient times, farmers have practiced irrigation using surface water from nearby sources for a variety of crops including Aman and a number of nongrain Rabi crops. There have been local Aman species/cultivars that required very low levels of supplementary irrigation. Traditional irrigation techniques have been used extensively. With the advent of green revolution in the mid-1960s and with the development of HYV seeds, people began to irrigate lands heavily. The initial results have been excellent in terms of grain yields. However, over the years, the requirement for fertilizers and irrigation has increased significantly due to the gradual deterioration in land quality due to the erosion of major nutrients, micronutrients, and organic carbon contents from the topsoil.
The surface water systems of the country are largely dependent on upstream countries: India, Nepal, Bhutan, and China. Increasing water withdrawal upstream and the diversion of water from the main transboundary courses reduced the flow in Bangladesh significantly during the dry months
(Rahman et al., 1990; Ahmad et al., 1994; Halcrow and Associates, 2001). Consequently, the possibility of surface water irrigation in the country has been reduced considerably.
To maintain self-sufficiency in food production, farmers have adapted to the use of modern irrigation techniques. Mechanized pumps have replaced the traditional methods of transferring water. Table 24.3 shows gradual development of various forms of irrigation with respect to time and technology. It is evident from table 24.3 that the total irrigated area more than doubled from 1985 to 2000. Moreover, the contribution of surface water and groundwater was almost equal in 1984-85. The recent expansion in total irrigated area was made possible due to about a threefold increase in groundwater irrigation, as against only about a 44% increase in surface-water irrigation during the same time. Currently, about 4.1 million ha out of 8.5 million ha of net cropped area (NCA) is being irrigated to cope with droughts. A recent study suggests that a total of 7.56 million ha could be brought under irrigation, which represents approximately 84% of NCA (Karim et al., 2001). Given the fiscal incentives provided for expansion of irrigation under the private sector, it is expected that more lands will be brought under irrigation in coming years.
Fortunately, Bangladesh has a reasonably good groundwater resource. The quaternary alluvium, the base material that raised the delta above sea level, constitutes a huge aquifer with reasonably good transmission and storage properties. Despite the growth in groundwater agriculture, heavy rainfall and annual inundation help the resources recharge substantially. It is estimated that 21 billion m3 of groundwater is available (MPO, 1991). However, the piezometric surface of the groundwater aquifers in many areas, especially in the western parts of the country, have lowered steadily because of continued withdrawal of groundwater to offset droughts (Hal-crow and Associates, 2001). In the areas dependent on the surface flows of the Ganges River, it is found that shallow tubewells have become inoperable in as many as 58 subdistricts due to the gradual lowering of aquifer surface. This is sufficient evidence that the management of drought in coming decades will be much more difficult.
Groundwater irrigation involves high production costs, especially for the poor farmers engaged in subsistence agriculture. Half of the farming community does not have any cropland; either they are sharecroppers, or they offer physical labor. For the sharecroppers, irrigation appears to be an economic burden which the owners do not share, but for which they receive the benefits.
Unfortunately, unlike flood, it is not possible to bear the loss due to drought. Often poor farmers borrow money at high interest rates, as high as 100%, to be repaid just after harvest of the standing crop (BUP, 2002). There are concerns that fighting droughts has caused high capital investment, which ultimately rendered many poor families indebted to local wealthy people. An accumulation of such debts often forces the poor farmers to migrate. Drought is therefore believed to have compounded the already endemic problem of poverty in rural Bangladesh.
AGRICULTURAL DROUGHT IN BANGLADESH 321 Table 24.3 Area under irrigation in Bangladesh
Irrigated area in different years (1000 ha)
1984-85 1989-90 1994-95 1999-2000
Shallow tube well (STW) Deep tube well (DTW)
586 287 16 889
1638 502 25 2165
Subtotal for groundwater
Surface water Low lift pumps Canals Traditional
Subtotal for surface water
351 147 384 882 1771
484 176 478 1138 2576
538 352 250 1140 3305
624 424 202 1250 4032
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