The irrational use of water in agriculture is often responsible for several problems concerning the depletion of water resources. Water resources sustainability has crucial for the existence of farming system which is dependent on the cropping pattern practices. This paper concerns the studies of existing water resource management and determines factors affecting decision making about water use and management within different farming systems. In these cases, a multi-criteria decision making model (MCDM) has been determined that aims at allocating efficient water and land resources to farms in the Ping watershed area in northern Thailand by optimizing a set of important socio-economic objectives which depend on sustainable agricultural (rural) development. The solution was found by using two analytical steps as follows: single objective optimization and compromise programming.
These resources include: land, labour, capital, fertilizer, pesticides and irrigation water. Existing cropping pattern included the inseason rice, off season-rice, vegetables (chili, pak choi, cauliflower, long bean, cabbage), soybean and sweet corn. Under the model cropping pattern conditions the in-season rice was produced for the household consumption and specially found in irrigated areas with storage dam. The model recommended that the suitable cropping pattern of the in-season rice followed by chili and long bean increased the gross margin two times. The amount of water used for the irrigation decreased by 6.84 percent from original 1,198,904 m3 at the existing cropping pattern to 1,116,902 m3 at the model cropping pattern.
However, in the case of the irrigated areas with water gates the model showed that the suitable cropping pattern was not different from the existing ones. However, the recommended model cropping pattern as the suitable cropping pattern consisting of the inseason rice followed by vegetables, sugar cane and perennial crops such as longan increased the gross margin three times while the water use increased only by 2.25 percent from the existing cropping pattern (from 1,374,655 m3 to 1,405,582 m3 at the model cropping pattern).
In the case of the rainfed areas the model cropping pattern recommended to grow the in-season rice, tobacco and longan on farm which increased the gross margin six times. However, the water using increased slightly from the existing on-farm water consumption (101,601.2 m3) up to 680,869 m3 as linked to the model cropping pattern.