Abstarct: Groundwater resources in Garmabdasht – Syahtalve region are important sources for drinking water supply for Gorgan City. Because of the relatively large groundwater extraction in this area, the yield of some of the production wells has reduced considerably and some wells have faced sever deterioration. In order to study the qualitative and quantitative changes in groundwater sources of Garmabdasht - Syahtalv, a series of statistical indicators have been used. The first is distance index and the second is discharge-distance index. The amount of discharge, reduction in the discharge and the concentrations of major ions in the water wells and statistical indicators have been standardized. Standardized data were plotted against each other and the regression line of the data has been drawn. Then, the slope and r-square for this line has been calculated. Finally, those data with considerable slope and correlation coefficients (99% level of significance) were selected for final evaluations. By using statistical indicators evaluation presented in this study, a simple and applied method is introduced to determine the effect of well structure on the reduction in discharges of wells. The results of this study show that the effect of wells structure to reduce the discharge of the wells can vary between 0 to 75 percent.