Assessment of Water Yield as an Ecosystem Service Using the InVEST Model: A Case Study of a Watershed in Western Iran

 

Water yield is a key ecosystem service that reflects the capacity of watersheds to regulate water availability under varying climatic and land use conditions. In this study, the InVEST Annual Water Yield model was applied to an upstream sub-basin of the Sefidrood watershed located in Kurdistan Province, western Iran, to assess the spatial variability of water yield and its relationship with land use patterns. Watershed boundaries were delineated using a digital elevation model and stream network data in ArcGIS. Potential evapotranspiration was estimated using the Blaney–Criddle method based on available climatological data, while precipitation surfaces were generated from regional rain gauge stations. Land use/land cover for 2023 was derived from Sentinel-2 imagery (10 m resolution) and Esri datasets. Plant available water content was calculated using global soil texture information. Model parameterization included the development of a biophysical table and the calibration of the Z parameter to reflect regional climatic conditions. Results indicate that annual water yield across the watershed ranges from 0 to 239.97 mm, with rangelands contributing the highest total water yield (90,656.7 m³) and orchards exhibiting the lowest contribution (47.2 m³). These findings highlight the strong influence of land use on water yield dynamics and provide a scientific basis for sustainable watershed management and ecosystem service optimization in semi-arid regions of western Iran.