Optimal Planning for Water Resources Allocation (Case study: Hableh Roud Basin, Iran)

Abstract

The world is facing severe challenges in meeting the rapidly growing demand for water resources. In addition,<br />irrigation water which is the largest use of water in most developing countries and arid and semi arid regions, will likely<br />have to be diverted increasingly to meet the needs of the households in urban areas and industry sectors whilst remaining a<br />prime engine of agricultural growth. A Linear Programming (LP) model has been developed to allocate the land and water<br />resources to different crop activities for maximizing the net return. Application of the model for the irrigation water<br />management revealed that in winter, 89.4% of available channel water was utilized, out of which 55.9% and 18.5% were<br />allocated for wheat and barley, respectively .The remaining 25.6% channel water was allocated for cotton and<br />watermelon. Since there were enough channel water supplies in this season, only 10.6% of available groundwater was<br />utilized. In the absence of constraint on conjunctive use, there would have been no groundwater exploitation, and 100% of<br />the channel water, which is much cheaper than groundwater, could have been utilized, if required. During summer season,<br />the entire quantities of water available in channel as well as groundwater resources were utilized. In this season, as there<br />was limited channel water supply, considerable part of the irrigation requirement was met from available groundwater.<br />Based on the LP analysis, out of total available channel water, 43.2% was allocated to cotton cropping, which was most<br />profitable as compared to all other crop activities, followed by 38.3%, 9.5% and 9% to crop activities including<br />watermelon, barely and wheat, respectively. Out of total available groundwater, 65.8% was allocated to cotton whose<br />irrigation water need was high and the remaining 34.2% was shared by wheat, barley and watermelon cropping activities.<br />The model predicts that in the case of changes in irrigation water supply, it will be economic to change the cropping<br />pattern.