Changes in watershed hydrological behavior due to land use comanagement scenarios

The changes in runoff and sediment load due to various approaches in land use management have recently received considerable attention. In the present paper, the impact of land use change under collaborative management framework on water and sediment load was investigated by combined usage of hydrologic modelling and land use maps. Three groups of stakeholders viz. residents, policy makers and executive organizations were involved in decision making process. Three prioritization procedures of Condorcet, Borda scoring and Fallback bargaining were elected to rank sub-watersheds and managerial practices. The impact of different managerial scenarios was assessed by applying time-area concept and through analyzing changes in important components of output hydrographs and sediment graphs. Results demonstrated significant agreement among stakeholder's attitudes and quantitative outcomes. The results illustrated obvious impact on runoff and sediment resulted from scenarios for land use management. So that, the impact on sediment load (with maximum reduction benefit of 19.41%) was significantly greater than that of runoff (with maximum reduction benefit of 8.07%). Manipulation of farmlands and poor rangelands and afforestation caused recognizable reduction on runoff and sediment. Rangelands restoration also satisfied socioeconomic status and environmental criterion of the study area. Considering basic differences in prioritization procedures, there were considerable agreement among stakeholders in land use management and practice prioritization. The results further indicated that the watershed management projects should focus on remediation of vegetation cover of the rangelands, which simultaneously tackles land degradation and improves economic condition. However, the present study revealed lack of proper connection between residents and authorities. Nevertheless, as a pioneer comanagement endeavor, the present qualitative and quantitative results facilitate group decision making and participated planning procedure at the watershed scale.