Land use optimization in watershed scale

Managing a watershed for satisfying the inhabitant's demand is a difficult task if one has to maintain a reasonable balance between usually conflicting environmental flows and demands. The solution to these complex issues requires the use of mathematical techniques to take into account conflicting objectives. Many optimization models exist for general management systems but there is a knowledge gap in linking practical problems with the optimum use of all land resources under conflicting demands in a watershed. In the present study, an optimization problem has been formulated for the Brimvand watershed, Iran, comprising ca. 9572 ha to find out the most suitable land allocation to different land uses, viz. orchard, irrigated farming, dry farming and rangeland targeting soil erosion minimization and benefit maximization.Soil erosion, net benefit and land capability maps were provided as inputs to formulate the objective functions and governing constraints in a multiobjectives linear optimization problem. The problem was then solved using the simplex method with the help of ADBASE software package and the optimal solution was ultimately determined. Additionally, sensitivity analysis was also conducted to recognize more effective land use in reducing soil erosion and increasing benefit. The results of the study revealed that the amount of soil erosion and benefit could, respectively reduce and increase to the tune of 7.9 and 18.6%, in case of implementing optimal allocation of the study land uses. The results of sensitivity analyses also showed that the objective functions were strongly susceptible to the constraint of maximum summation of irrigated farming and orchard areas.