Analysis The Temporal Variation of Water Table Elevation Under The Impact of Precipitation and Consumptions by Using Regression Model and Differential Equation

In order to better exploitation of the available water resources and to prevent water crisis increment, predicting the changes in water resources through different methods will be of great importance. In this study, monthly data of water table elevation, consumptions and precipitation during the period of 2001 to 2011 for Ajabshir plain were used to predict the water table elevation through two methods. The first method is to solve the application of partial differential equation for consecutive time steps and the second one is the proposed regression model. The finite difference method was used for the temporal solution of the differential equation which leads to gain a correlation coefficient of 0.9 and an RMSE of 0.41 between estimated and observed values of groundwater levels. To determine the time period for the effects of precipitation and consumptions on the water table elevation, the cross correlation function was used; which indicated great impact of precipitation and consumptions on water table elevation with one and two lags respectively. Finally the general relationship between these three variables with time period effects through a multivariate nonlinear regression model was obtained via a correlation coefficient of 0.93 and RMSE of 0.35. According to the evaluation criteria derived from two methods, the multivariate regression model was selected.