2-LEVEL OPTIMIZATION MODEL FOR LOWER INDUS BASIN

The present study aims at the development of a model to schedule the s owing dates of the crops in such a manner that the peak water requirem ents of different crops are more uniformly distributed over different months and hence, more area can be irrigated for a given canal and tub e well capacities. For this purpose, a two-level optimization model fo r optimal use of surface and groundwater has been developed. In the fi rst level, the model gives optimal cropping patterns and monthly water withdrawals from canal and tube well for a given set of sowing dates to maximize the net economic returns. At second level, the sowing date s are varied within the allowable limits and the optimized sowing date s are obtained using an integer programming model. The sowing dates at the first level are then taken as the sowing dates obtained from the second level. The process is repeated until it converges. The sensitiv ity analysis for some of the parameters is also done. The model is app lied to Dadu canal command of Lower Indus Basin. The results show an o verall increase of 40% in the crop intensities and 38% in the benefits over the existing ones by using the two-level optimization model. (C) 1998 Elsevier Science B.V.