4. APPROACHES TO WATER USES FOR SUSTAINABLE AGRICULTURE

In an carlier prcsentation (Vo-Tong, 1996) I suggested a sustainable path to fo od security, ii,tking full attention to the limiting natural resources, particu larly water. Sustainable agricultural development must start with a farmlng sys tem approach with accounts for every resource input to the whole system includi ng human, natural, and socio-economic resourses. The general guideline would provlde equal opportunity to all producers. for food grain producers, particul arly rice farmers, continuously improved technologies for increasing grain yie ld and lower production cost must be available. Here, the choice of technology should be labor intensive and low input affordable by the poorest farmers. Rec ently. the sustainable agricultural and rural development (SARD) approach advoc ated hy the Food and Agriculture Organization (FAO) has been used, based on res ource man-agcment domain (RMD) approach, in the technology generation and selec tion process. While scarce arable lands should be devoted to food grain crops, farmers should be en-couraged to use non-rice food crops (pulses, root crops.) in rice-non-sultable lands, in home or school gardens to provide feeding materi als for livestock and fishery production.

The watering of crop lands hereto forth should take a new approach to improve t he efficiency of water resources. The following suggestions may be considered most appro-priate in future water resources development for agricultural produ ction:

4.1 Rehabilitation of existing irrigation and drainage systems.

Throughout Asia, numerous irrigation schemes were constructed with assis tance from four main donors, the World Bank, the Asian Development Bank, the U.S. Agency for International Development, and the Japanese Interna tional Coopera-tion Agency. However, these investments were cut to half since 1990 com-pared to the late 1970s since the loans of this kind was difflcult to pay back, and that the donors are constantly under the sur veillance of environmentalist groups. The efficiency of these irrigation systems, according to a recent World Bank survey (Jones, 1995), measure d in terms of internal rate of return ranged from 5-56%, demonstrating a wide variability which makes it difficult to generalize about irrlgatio n system performance. An assessment by Rosegrant et al ( 1987) of econom ic returns to 51 irrlgation systems in the Philippines showed that while small-scale irrlgation had slightly higher average returns than medium and largc scale irrlgation, the dlfference was insignificant because of large varia-tion in system performance. Furthermore, the authors confirm ed that the over-all irrigation efficiencies in developing countries are low, ranging from 25-40% for Thailand, Philippines, and Mexlco, to 40-4 5% for Malaysla. For compari-son, the overall irrigation efficiencies fo r Japan, Taiwan, and Israel were from 50 to 60a/o (Rosegrant and Shetty, 1994). The inefficiencies of Asian irrlgation systems can be attributed to poor management of the system by the government agency and the irres ponsibility of the users. In Vietnam, virtually all lrrigation canals ar e earthen, irresponsible farmers broke open a side of the canal to let