Assessing Contribution of Human Activities and Climate Variability on Groundwater Changes (Case Study: Mahidasht Aquifer, Kermanshah Province, Iran)

Revealing the contribution of each of the climatic and human factors can help the management of water resources. Firstly, trend analysis and change‐point tests were performed to determine the status of the parameters affecting the groundwater resources of the Mahidasht aquifer during the period from 1981 to 2019 by using statistical methods and the Pettitt test. The GMS model was calibrated as a tool to simulate the Mahidasht aquifer system. After determining the change point, modeling of the groundwater level before and after the change point was done using the GMS model. By removing the effect of human factors in the model, the contribution of the effects of climate variability and human activities on groundwater was obtained. The results showed that there was no significant trend in annual rainfall, but the annual runoff has a significantly decreasing trend at the confidence level of 99%, and the trend of the groundwater level is also significantly decreasing at the confidence level of 99%. Pettitt change point test showed precipitation without a change point, but the runoff in 1998 and the groundwater level in 2001 had a change point. Finally, the modeling of the aquifer showed that the contribution of human activities in the reduction of the groundwater level of the Mahidasht aquifer was 78 and climate variability is 22%.