Saving scarce water

Nepal C. Dey, Sujit K. Balab and Seiji Hayakawa carried out an excellent economic exercise on wastage of water and the ways to wane it. Published in the Water Policy 8 (2006), the paper produces food for thoughts for those warring on the availability of water; hence needs reproduction, even at the cost of paraphrasing, for the policy makers in Bangladesh. Economic analysis, which is defined as maximising social net benefits with limited resources, often requires improvements in water management even when basin-wide measures of irrigation efficiency are relatively high. So, proper irrigation water management practice becomes a very important tool for resolving some issues. It has been revealed that through proper on-farm irrigation water management practices, and the researchers reckon, it is possible to increase the irrigated area by 29 per cent and to irrigate the area with the same volume of water and save irrigation costs by up to 25 per cent.
Although rapid expansion of the irrigated area has taken place over the last few years, there are indications of poor performance and low water use efficiency in the existing system. Good performance of existing irrigation facilities in Bangladesh is a must for sustainable food production in the country. Existing water management practices must also be improved to maintain favourable soil fertility, crop intensification and diversification. The government here has given due recognition to the importance of introducing and applying appropriate techniques and technologies at the farm level of irrigation water management and has considered it a potential area for ensuring food security, employment generation and alleviation of poverty through intensification and diversification of agricultural production.
Food deficit and waste of water are positively correlated. The total loss of water has been computed by subtracting total crop consumption of water from the volume of water lifted. The actual volume of water required for irrigation was calculated through computation of crop consumption of water, while the volume of waste water was computed by subtracting this volume of water (crop consumption from the total water lifted).Taking account of the recommendation, 1997, 52 per cent of wastewater may be saved if proper irrigation practices are followed. An area of 1.82m ha may be irrigated with the waste water saved. If 5,185 cubic metre of water is recommended for one hectare of land for crop growth and if it costs US$77, an economy of US$140m may be made by using waste water, which is saved.
The waste water to be saved would be used for irrigation of additional area of about 1.82m ha, which would provide about 9.97 m metric tonnes (MT) of additional crops. The cost of production per ha is US$268, the yield per ha is 5.48 tonnes and the price of one MT is US$103.4. So, a net financial benefit is computed to be US$543 million. About 30 per cent of Aman rice (summer-type rice) that is, about 3.3m MT is affected owing to lack of supplementary irrigation. By carrying out supplementary irrigation for only of 45 per cent of affected Aman (summer-type) rice, an additional Aman rice yield of about 1.485m MT may be grown and a total financial benefit of about US$155 million may be accrued. The price of 1MT rice is US$103.4.Irrigation equipment like the deep tube-well (DTW), the shallow tube-well (STW) and the low lift pump (LLP) are diesel driven and at present operate with an efficiency of about 60 per cent, which is quite low. The operation of irrigation equipment may be improved at least by 20 per cent by saving the cost of operation and maintenance, fuel, man power, and so on, and a total saving of about US$107.6million may be achieved. Bangladesh has natural and man-made water bodies of a total area of about 334,649 ha. Silting up of these water bodies is gradually reducing their capacity for preserving water. Preserving capacity of water bodies is 6,693m cubic metre. It is possible to use about 50 per cent of this capacity, that is, 3,346.5m cubic metre of water, bringing the area under irrigation to about 0.64 Mha through excavation. The area brought under irrigation may provide a yield of about 3.5m MT, which in return may provide a financial benefit of about US$362m.
Minor irrigation systems also incur losses. Available evidences showed that owing to the unplanned installation of minor irrigation equipment , the efficiency of the system, at present, is only 57 percent. If it is possible to achieve an increase of only 20 percent, then only economy of diesel and electric energy may save about US$38 million in this sector. Most minor irrigation systems have inappropriate water control structures, poor canal systems and inadequate drainage facilities. From the field study, it is seen that the total volume of water lifted for irrigation is almost double that of requirement for water. This occurs because of the lack of proper technical knowledge. More than US$140 million could be saved if irrigation was carried out according to crop water requirements, proper irrigation scheduling and water management.
Huge amounts of irrigation water are lost in conveyance and distribution systems. By reducing this system loss of water, it is possible to irrigate more than 3.0m ha of crop land and produce an additional 1,735m MT of crops and additional economic benefits may be equivalent to $543 million. The take home lesson is that save water, save life.
The writer is a Professor of Economics at Jahangirnagar University. [email protected]