In this study, an overview of the methodology and case studies of climate change impact modeling studies on groundwater are presented. Impact modeling studies on groundwater are relatively new, and innovative approaches with respect to climate data analysis, downscaling of GCM projections, groundwater recharge estimations are still being developed. Some challenges lie ahead for more reliable climate change impact assessments. For example, there is considerable uncertainty about the predictions made by GCMs, specifically precipitation predictions vary between different GCMs. Moreover, uncertainties exist for groundwater flow modeling because of aquifer heterogeneity and the difficulty to quantify certain hydrogeological parameters. These uncertainties in data and models can be mitigated by opting for stochastic modeling approaches that provide means to quantify uncertainties. Evaluating multiple GCM model results and aggregating them can be helpful in reducing the uncertainty in climate data.
Furthermore, the modeling methods on key processes like recharge and evapotranspiration need to be improved. With respect to recharge, other mechanisms such as irrigation return flow, leaking pipes in urban areas and losing surface water should also be considered for a more rigorous modeling study. Projections of future irrigation water demand, groundwater withdrawal for domestic and industrial use, future land use and future levels of surface water features are other improvements that can be considered. Lastly, if data and conditions permit, studies based on a transient groundwater flow modeling approach should be conducted because climate change impact studies based on steady-state simulations have limitations in representing boundary conditions. It is preferable to use them for assessing sensitivities before implementing more rigorous and data-intensive transient modeling.
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