Water Balance Analysis for Reservoirs through Remote Sensing: A Case Study of the Karun (IV) Reservoir in Iran.

Dams are essential for effectively managing water resources as they serve multiple vital purposes, such as water storage, flood control, hydroelectric power generation, recreation and tourism and ecosystem regulation. The rising number of reservoirs, prompted by population growth, and the urgency for climate change adaptation and mitigation strategies emphasize the importance of developing efficient methods for calculating reservoirs water balance. In this study, we propose a remote sensing-based method for water balance analysis, aiming to facilitate the monitoring and management processes of water storage. The Karun (IV) reservoir, a dam situated in the southwestern region of Iran, is selected as the case study for this research. A conceptual rainfall-runoff model is employed to simulate the daily inflow rate of the reservoir by utilizing hydrological data obtained through remote sensing techniques. This data includes various parameters such as precipitation, evaporation and transpiration, soil moisture, vegetation, and land use. Moreover, a sensitivity analysis of model parameters is conducted to assess the significance of each parameter and simplify the model for future applications. Reservoir water evaporation is estimated by utilizing the reservoir area of the dam, which is obtained from the NDWI water index and the evaporation rate extracted from the WAPOR dataset. Then, altimetry data and reservoir area data are utilized to calculate changes in water storage. Finally, the water balance equation incorporating the calculated balance elements above is applied to determine the daily output of the dam reservoir. This study showcases the utilization of remote sensing data in estimating the output of the Karun (IV) reservoir. The accuracy of the proposed method is verified through comparisons with field data, making it a valuable tool for reservoirs where field data collection is costly or challenging.