Effects of Land Use Changes on Water Balance in Taleghan Catchment, Iran

In recent years, changes in catchments water balance due to land use management have become the main concern of water resources authorities in Iran. Due to rapid population growth and land use changes, especially construction of Taleghan dam, Taleghan catchment has undergone rapid changes such as urban development, declining of rangelands, and deterioration of environment and erosion of soil resources by cultivating the hilly lands along the slopes for wheat or barely production. The extent of rangeland area shrinkage is substantial: from ۸۳% during the early stages of dam construction down to ۳۵% by the end of the study period. The ‘good’ rangeland area decreased to ۵.۹۰% from ۳۴.۴۹% while the poor rangeland increased from ۱۹.۰۴ to ۲۳.۳۵% during the period of ۱۹۸۷ to ۲۰۰۷. These changes could potentially have devastating impacts on water balance of the catchment. The main objective of this research was to examine the effects of land use changes on water balance of the Taleghan catchment before and after the dam construction. The Soil and Water Assessment Tools (SWAT) model was applied for predicting water balance in the middle and outlet of the catchment. The main input data for simulation of SWAT are Digital Elevation Model (DEM), soil type, soil properties, and hydro-climatological data. Comparing the water balance for ۱۹۸۷'s land use for the middle station (Joestan) and the outlet station (Galinak) showed that surface runoff was ۲۱% of the precipitation for the upper part of the catchment and ۳۳% at the outlet. Total groundwater and lateral flows were ۳۷ and ۱۹%, respectively. The water balance at the outlet was predicted for two other scenarios of ۲۰۰۱ and ۲۰۰۷. The results showed ۷.۳% increase in surface runoff and ۱۱.۳ and ۱۱% decrease in the lateral flow and groundwater flow, respectively. These results indicated progressive increase in surface runoff and decline in interflow and groundwater flow.Therefore, one of the main challenges facing development planners is the control of the accelerated degradation of the natural resources that has been taking place during the last decade.

کلیدواژه ها:

Land use ، Taleghan ، SWAT ، Water balance