Potential groundwater recharge during floods

Groundwater constitutes 30% of fresh water reserves on Earth. It is important as a source for drinking water and irrigation due to its good quality. For many aquifers in arid regions, long-term groundwater extraction has put in risk its sustainable use. Thus, it is relevant to understand and quantify processes that contribute to sustainable groundwater recharge. Most recharge to aquifers in arid regions occurs during flood events that happen with a frequency of a few years to decades. Paleo-climatic records show that intensity and frequency of floods have been particularly variable during periods of climate change. Therefore, understanding how floods could impact the magnitude and occurrence of groundwater recharge to aquifers in arid regions is relevant for improving water management strategies and assessing aquifer vulnerability to pollution from surface streams. Direct measurement of infiltration during flood events is difficult, so it is common to complete analyses with numerical simulations. We present results of detailed numerical simulations of infiltration through the vadose zone during flood events. We use the results of the simulations to characterize infiltration patterns and quantify potential for recharge to aquifers considering different subsurface conceptualizations, from simple homogeneous to more realistic multi-scale heterogeneous sediment distributions. We also make a few additional general comments for practical applications.