optimal planning for water resources allocation (case study: hableh roud basin, iran)

the world is facing severe challenges in meeting the rapidly growing demand for water resources. in addition,irrigation water which is the largest use of water in most developing countries and arid and semi arid regions, will likelyhave to be diverted increasingly to meet the needs of the households in urban areas and industry sectors whilst remaining aprime engine of agricultural growth. a linear programming (lp) model has been developed to allocate the land and waterresources to different crop activities for maximizing the net return. application of the model for the irrigation watermanagement revealed that in winter, 89.4% of available channel water was utilized, out of which 55.9% and 18.5% wereallocated for wheat and barley, respectively .the remaining 25.6% channel water was allocated for cotton andwatermelon. since there were enough channel water supplies in this season, only 10.6% of available groundwater wasutilized. in the absence of constraint on conjunctive use, there would have been no groundwater exploitation, and 100% ofthe channel water, which is much cheaper than groundwater, could have been utilized, if required. during summer season,the entire quantities of water available in channel as well as groundwater resources were utilized. in this season, as therewas limited channel water supply, considerable part of the irrigation requirement was met from available groundwater.based on the lp analysis, out of total available channel water, 43.2% was allocated to cotton cropping, which was mostprofitable as compared to all other crop activities, followed by 38.3%, 9.5% and 9% to crop activities includingwatermelon, barely and wheat, respectively. out of total available groundwater, 65.8% was allocated to cotton whoseirrigation water need was high and the remaining 34.2% was shared by wheat, barley and watermelon cropping activities.the model predicts that in the case of changes in irrigation water supply, it will be economic to change the croppingpattern.