Groundwater Resources Balance Estimation Using Remote Sensing Approach: A Case Study of Qamshe Plain

One of the methods for groundwater monitoring is the calculation of the water balance, which provides important information about the status and changes of aquifers. However, estimating the components of the groundwater balance is challenging, which can reduce the accuracy of the results. This study aims to improve the accuracy of evapotranspiration estimation in the groundwater balance using remote sensing, which leads to better estimation of return flow and infiltration from rainfall. Consequently, the groundwater balance is calculated with higher accuracy. For this purpose, data from observation wells, precipitation, withdrawals, rivers, and aquifers in the Qomsheh study area between 1992 and 2016 were used to evaluate the groundwater balance. A conceptual water balance model and the WaPOR remote sensing product were used to estimate ET. Finally, the observed water balance was compared with the calculated water balance. The results showed that during the study period, 40.54 million cubic meters (MCM) of water infiltrated into the aquifer through precipitation, irrigation, and surface flow. In contrast, 262 MCM of water was withdrawn from the aquifer, of which 105.53 MCM returned to the aquifer. Also, 10.21 MCM of water entered as lateral flow and 0.73 MCM of water exited the aquifer. The groundwater balance was estimated to be 120.02 and 119.09 MCM using the computational and observational methods, respectively. Comparison of these two water balances shows that using WaPOR remote sensing products in estimating the components of the water balance reduces uncertainty and increases the accuracy of calculations in the Qomsheh study area.