Analysis of Temporal and Periodic Changes of Groundwater Depth and Nitrate Concentration Using Time Series Modeling (Case Study: Kabudarahang Plain)

In this study, ground water level fluctuations and Nitrate concentrations of kabudarahang aquifer were investigated with application of time series models for modeling of ground water quantity and quality parameters. For data regarding the status of groundwater level and Nitrate concentration fluctuations in project area time series models were used to forecast the groundwater level and Nitrate concentration. Residual error analysis, comparison of observed and calculated ground water levels and Nitrate concentrations performed and finally a prediction model for ground water conditions in Kabudarahang aquifer developed. Predicted values were calibrated by the Box-Jenkins, Holt Winters and extrapolation axes models. A residual error analysis, based upon calculated and observed groundwater level and Nitrate concentration performed as a model verification tool and finally the Box Jenkins models were evaluated through portmanteau method and Akaike information criterion. The model verification results showed that the SARIMA model is the optimum algorithm to simulate seasonal input data variables. Model results showed that the groundwater level in this aquifer will endure a 6 meter decline in four upcoming years and indicated that the maximum Nitrate concentration would reach 50 mg/l in Bahman and shahrivar of 1390.