Quantifying Spatio-Temporal Changes of Groundwater Level in Arid Regions

Groundwater is known as the most important source of fresh water and its management is extremely important in arid and semi-arid regions, where there is a scarcity of surface water due to the lack of enough rainfall. Excessive water harvesting and improper water management can cause a decline in groundwater levels, which can lead environmental, social and economic crises. Therefore, this valuable resource must be exploited correctly and accurately. To achieve this aim, it is necessary to know the extent of its changes. Hence, in this study, the groundwater level changes in Semnan and Damghan plains, Iran have been investigated. For this purpose, Piezometric well data from 1994 to 2018 were used. Groundwater level zoning in two study regions was carried out using Inverse Distance Weighting (IDW), Kriging, and Co-kriging methods and the best zoning method was selected by Taylor diagram and Nash-Sutcliffe Model Efficiency Coefficient (NSE). Results of these two methods indicated that IDW and Kriging models are the most accurate way to zoning the groundwater level in Semnan and Damghan plains, respectively. The results of groundwater level maps showed that both plains have a decreasing trend in groundwater level over the time. Most of the water level dropping has been occurred in the east and south of Semnan plain and the eastern parts of Damghan plain which may be due to the concentration of agricultural areas in these parts. In Semnan plain, the depletion of groundwater is from 1.59 to 33.56 meters in April and from 1.55 to 35.40 meters in October, while in Damghan plain is from 3.76 to 30.97 and from 3.85 to 30.60 in April and October, respectively.