Estimating Well-Based Injection Capacity for Managed Aquifer Recharge Feasibility Mapping: A Case Study in Minnesota, USA

Abstract:

In recent years, managed aquifer recharge (MAR) has become an important tool for water resources management in various geographic and socio-economic contexts. However, practical guidelines regarding the assessment of the amount of water that can be injected through wells remain limited. In this contribution, we propose a simple method based on the Theis solution describing the hydraulic head response to pumping to estimate well-based injection capacity at every point of an aquifer, and apply it to the Buffalo aquifer located in northwestern Minnesota, USA. The parameters required for injection capacity estimation are aquifer transmissivity and storativity, maximum allowable head change, injection duration and well radius. Transmissivity and maximum allowable head change are considered spatially variable, and the other three parameters (storativity, injection duration and well radius) are assumed constant. The results show that the injection capacity is significantly higher in the portion of the aquifer with higher transmissivity and higher allowable head change. Due to seasonal fluctuations in groundwater level, the maximum allowable head change varies seasonally. However, the difference in the maximum allowable head change for wet and dry seasons in Buffalo aquifer is small, and this causes insignificant differences in the injection capacity. We then discuss the magnitude of the injection capacity in view of the water requirements of the Fargo-Moorhead area, which is the main potential beneficiary of MAR in the Buffalo aquifer. Assuming an injection duration of one month and considering the 90-percentile value of the injection capacity, 23 wells are required to inject a volume of water equal to three months of public water supply for the Fargo-Moorhead area. This result, when combined with a socio-economic analysis, can help decision makers to assess the relevance of implementing MAR in this area. This study illustrates the value of carrying out a first-order assessment of well-based injection capacity for MAR feasibility mapping.

Acknowledgements: The authors acknowledge support from National Research Foundation of Korea (NRF-2020M3H5A1080712) and Minnesota Environment and Natural Resources Trust Fund, United States as recommended by the Legislative-Citizen Commission on Minnesota Resources.