annual water yield estimation for different land uses by gis-based invest model (case study: mish-khas catchment, ilam province, iran)

Fresh water supply and its security encounter a high level of fluctuating variability under global climate changes. to address these concerns in catchment water management, a good understanding of land use/cover impacts on the hydrological cycle affecting water supply is crucial. the objective of this study is to define a model to investigate the impact of existing land use/cover on water yielding in mish-khas catchment of zagros region, ilam province, iran. in this research, a water yield model of integrated valuation of ecosystem services and tradeoffs (invest) was employed to estimate annual water yield in the catchments as a basic foundation for policy and decision making. the input data set included land use/cover layers of the region produced in 2016, average annual precipitation and potential evapotranspiration from 1986-2016, soil depth, plant available water content and land use/cover bio-physical database. based on the results, total annual water yield was estimated 30.2 million m^3 for the whole mish-khas catchment. the annual water yield percent for rangeland, forest, farmland and orchards land uses was 57%, 31%, 8.6% and 3.4% of the total water yield of the catchment, respectively. in addition, the results showed that the farmland had the highest water yield (2449 m^3/ha) followed by forests (2269 m^3/ha), orchards (2254 m^3/ha) and rangeland (2196 m^3/ha) land uses. in terms of water distribution, the northern regions with a volume of 2315 m^3/ha had higher water yield than the southern regions (2210 m^3/ha). the results also indicate that a gis-based invest model is a useful instrument to identify more suitable areas for watertable recharge.