Abstract:
Heavy withdrawal of ground-water has been identified as a serious problem affecting ground-water quality, threatening agricultural productivity and thereby the income of the farmers in the Jaffna district. A two stage mathematical model was developed to determine the optimal use of water throughout the irrigation season and to suggest an optimal cropping pattern and suitable policy changes required to improve ground-water use in the Valigamam region of the Jaffna district. In the first stage, ground-water recharge and crop water requirements were estimated for ten years from 1971 to 1980. The information generated from the hydrologic models was entered into a linear programming model in a dynamic form at the second stage, with other resource constraints. Economic data from 1980 to 1989 were used in the economic analysis for five Agrarian Service Centre (ASC) areas in the Valigamam region. The results of this study show that water was over utilized in Nallur, Keerimalai and Tholpuram, but under utilized in Puttur and Uduvil ASC areas. The results of the optimization exercises reveal the need to increase institutional credit and for family labour to be fully utilized for a higher return. Significant changes were noted in the mixed cropping of the average optimal plans over the existing plans at all recharge levels. This suggests potentials for increasing the total cropped area and net returns, particularly, in the Puttur and Uduvil ASC areas. This leads to 26% more intensive use of land and 14% income increase from agriculture, and the effective utilization of water in the whole study area. The findings will be useful to policy makers and administrators in promoting and implementing development plans in the study area.
