Quantifying the impact of urban runoff injection on groundwater enhancement in a semi-arid environment using SWMM and MOFLOW Model

In the urban area, surface runoff can be utilized effectively to improve groundwater table through rainwater harvesting. The main aims of this study were to:1) investigate the potential of the surface runoff to inject into Urmia aquifer and increase groundwater recharge of this aquifer using SWMM - MOFLOW Model, 2) to investigate the quality of the urban runoff for aquifer recharge, and 3) to investigate the feasibility and effeteness of the artificial recharge via injection wells in a semi-arid area. Urmia city with an area of 930 Km(2) is located at the West of the Urmia Lake in the North-West of Iran. The study aquifer has a negative groundwater budget, while some of the sub basin in the study watershed is prone to flood in the falling season. In this study, based on the location of surcharged channels, the quantity of rechargeable surface runoff to inject into the aquifer was estimated via SWMM model. Calibrated MODFLOW model was applied to predict the potential effects of the injectable water runoff on the groundwater surface. Estimated runoff by SWMM model was used as the input of the MODFLOW model. The quantity of the heavy metals (Fe2+, Zn2+, Mn2+, Pb and Cu2+) TDS and pH were measured to control runoff quality. According to the results, 1.12 million cubic meters (MCM) per year of runoff can be injected to the aquifer via 9 designed injection wells. This amount is equivalent to the annual loss of the aquifer (about 20 centimeters per year) that can ensure the stability of the aquifer in the injection area.