Assessment of groundwater recharge in a semi-arid groundwater system using water balance equation, southern Iran

Estimation of the groundwater recharge is extremely important for the groundwater management in semiarid regions. A simple water balance equation is used for quantifying the total annual groundwater recharge during 8 water years (from 2002 to 2010) in the Burazjan aquifer, south Iran. Total annual groundwater recharge was estimated using two approaches: (1) sum of the known inflow components to the aquifer system, and (2) sum of outflow components from the aquifer and annual change in the aquifer storage. Comparison of the results from two approaches shows a considerable difference with an average of 91.30 million m3/year for the annual recharge. This difference could be caused by (i) error in quantifying the inflow components and/or (ii) missing an unknown inflow component. Sensitivity analysis reveals that the difference in the estimated annual recharge is more than the estimated 20% error in quantifying the components of the water balance equation. However, considering the geological setting and previous investigations, a missed inflow component related to Burazjan Fault is proposed. Contribution of this inflow component in annual groundwater recharge ranged from 33.25 to 132.90 with an average of 91.30 million m3/year.