1. Abstract
Dams, are mainly use to supply, transmission and distribution of optimum crop water
requirements. However, the dams could have adverse effects on the upstream and downstream of
the plain. So before construction of any dam, must be evaluate its environmental impact, especially
in the case of ground water resources. In recent decades the use of computer models as a cheap
and quick way to simulate the behavior of groundwater has noticeably development. In this study,
the monthly data of 12 observed groundwater wells during 2002 to 2011 in the Shahrchay aquifer
were used. The years of 2002 to 2006 were evaluated to analyze the situation Shahrchay aquifer
before the dam and the years of 2007 to 2011 were evaluated to analyze the situation Shahrchay
aquifer after the state of the dam. After collecting the data needed to simulate aquifer (unit
hydrograph, Information geophysical, hydrological and hydrogeological) to simulate the aquifer
was done. For this, first by changing the model parameters including transfer coefficient and
hydraulic conductivity, model were calibrated and validated, and after calibration, the model was
simulated groundwater. Evaluation of groundwater simulation model showed that the accuracy of
model simulation data are varies depending on the geographical location of stations, as in most of
the stations in the border defined in the model, model to estimate the groundwater level is less than
the rest. With more accurate defined parameters during calibration computing error in the
construction of dams can also be reduced. Although the error rate for both before and after
construction of the dam is negligibly and can use this software for simulation of groundwater in
Shahrchay plain and other regions of the province and the country with similar characteristics.
Keywords: Groundwater, Shahrchay plain, Shahrchay dam, MODFLOW