Parametrization of River Aquifer Exchanges Enhancements in Managed Aquifer Recharge for Baseflow Restoration

The enhancement of stream flow has not been considered an objective in Managed Aquifer Recharge (MAR) projects due to the absence of a framework for quantifying River-Aquifer Exchange improvements. This work employs a numerical approach to assess the baseflow enhancement potential of a site. A novel metric, called the Baseflow Restoration Index (BFRI), has been developed to calculate the percentage increase in baseflow resulting from a unit rate of water injection.

Additionally, the capacity of the aquifer to be recharged has been quantified using a proposed metric known as the Permissible Aquifer Recharge Capacity (PARC). The PARC is defined as the maximum allowable rate of water injection at a site, taking into account the constraints of injection duration and permissible water head. By combining these two metrics, it is possible to determine the maximum potential baseflow enhancement achievable through the use of an injection well at a specific site.

The proposed metrics were applied in the Varuna River Basin, India, to evaluate the baseflow restoration potential of MAR projects. A straightforward TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) method was utilized with the calculated metrics to rank the sites based on baseflow enhancement, groundwater storage improvement, and overall project cost. This framework employs a 3D-integrated numerical model of surface water and groundwater in the Varuna River Basin to determine the proposed metrics.