groundwater modeling for estimation of the recharge rate and identification of appropriate recharge sites in damghan plain, iran

water is the main option of any development, so having an accurate management of groundwater is necessary. this study has been done in damghan sedimentary plain in iran, which is located in northwest of semnan province. the main objective of this research was to estimate the rate and right site of recharge in damghan plain to prevent the aquifer from decreasing the water table. for this purpose, the monthly data of observation wells in a water year from september 2009 to august 2010 were prepared. next, the type of aquifer, horizontal hydraulic conductivity (k), and the height of top and bottom layers were provided. finally, the aquifer has been simulated by modflow in two states: steady and transient. after simulation by application of different recharge rates, such as 11, 21 and 31 million cubic meter (mcm), it became clear that the fluctuation of water table on the southwest of the plain is less than the other areas, so it is considered as the right site of recharge. meanwhile, the water table showed no significant change as a matter of recharge 11 and 31 mcm rates, but it displayed a considerable enhancement by adding 21 mcm recharge rate. therefore, the study revealed that the appropriate rate of recharge is 21 mcm.