Abstarct: Recharge from precipitations is considered as the main and most important input to the most of the aquifers. In addition, it is the most important parameter of the water budget which is required in most hydrological and hydrogeological studies to groundwater. Instead of numerous investigations on recharge evaluation in the past few decades’ recharge amount estimation is difficult. Determining the exact amount of aquifer recharge due to the role of various factors and in unknown quantities is very difficult and practically nearly impossible. However, with increasing accuracy in the study of some of these parameters, recharge estimations accuracy can be improved to an acceptable level. baxsed on the literatures and evidence in many regions recharge is seasonal and, in other words, all events of precipitations don’t have the recharge capability. By assessing the characteristics of rainfall in any region, a recharge threshold can be determined for rain form of precipitation. Investigating the precipitations isotope content at 5 stations with different elevations indicates that the isotope contents of precipitations in Haraz basin is fallowing δD (‰) =66δ18O (‰)- 8.48 trend. Summer rainfalls have the heaviest and the winter time precipitations have the most depleted isotope content. Hydrochemical study of precipitation indicates the high concentrations of the main elements in summer and the lowest amount of these elements in the winter. The isotopic studies of the karst springs indicate that the isotopic composition of most springs are very similar to that of snowpack samples. This indicates the dominant role of snowmelt derived water in the recharging of karst aquifers. Studies carried out on the rain events and springs isotope time series in dry period indicates in springs catchments dominated by north facing (South of Lasem) or both south and north facing slope (Nemarstagh and Lar) some changes observed in isotope contents while those dominated by south facing slope (North of Lasem) showing no sensible change. In this area, rain events higher than 15.6 mm affect the isotope contents of the springs which had a 17.2 mm of excess moisture. If the excess moisture condition reach around the 17.2 mm it has capability to effect the isotope signature of the springs water and in dry season will lead to enrichment of the spring’s isotope content. baxsed on 27-year data at Polour station annual precipitation ranges from 298 to 857 mm which precipitated in average of 66% and 34% in the form of snow and rain, respectively. Considering the rain events in study period with regards to the excess moisture indicates that in average 28% of the precipitations in the form of rain are above this threshold. Potential recharge baxsed on type of precipitation are 85% and 25% for snow and rainfall, respectively. Potential recharge in carbonates of central Alborz ranges from 46% to 76% of annual precipitation. GIS used to develop the lithological, faults and fractures, vegetation cover, soil cover, karstification index map and slope directions maps to evaluate the relative effects of spatial parameters on recharge. After classification of the laxyers they have been overplayed to determine the recharge possibility in each location and finally it has been compiled with potential recharge. Recharge values to the limestone using overlaying method ranges from 30% to 90% of the potential recharge.