Understanding the quality and rate of recharge on uncultivated landscapes under natural and enhanced conditions

Background/Need

Groundwater recharge is the input to aquifers, which defines the sustainability of aquifer resources relative to the (output) demands from humans and the environment – i.e., supporting river flow, pumping demands, and other groundwater uses. The rate of groundwater recharge is dependent on several changing factors, including precipitation rates and types, evaporation rates, the permeability of near-surface materials, the consumption of water by plant species, and presence of snow and frozen ground conditions. Changes to climate during the 21st century are already revealing themselves in terms of increases of rain-on-snow days, increases in above-0°C winter days, and higher recurrence of large storm events (>1” precipitation). Increased pumping by agriculture and industry (e.g. power and associated water demand for data centers), and migration to “climate havens” such as the Midwest similarly suggests that there is a need to prepare for the future with increased groundwater storage and availability. This project investigates methods of implementing “enhanced recharge” to provide greater high-quality, sustainable stores of groundwater. To date, most projects investigating enhanced recharge techniques have focused on the arid west, where water scarcity provides strong economic motivations for projects, or on the east coast as a method to combat saltwater intrusion. Similarly, many if not most recharge enhancement projects have been focused in urban areas where proximity to population centers facilitates regular maintenance and monitoring of operations. With a humid continental climate, vast minimally-developed land area, and significant shrubland and forest cover, Wisconsin’s landscape provides an opportunity to source high-quality water for enhanced recharge. With most land area in Wisconsin’s (and indeed, the nation) being rural, effectively enhancing groundwater recharge must necessarily consider the realities of implementation and monitoring in rural settings.

Objectives

This project investigated a novel approach to enhancing recharge using shallow, small-diameter borings (<2” diameter, <10 ft depth). These boreholes, which allow water inflow but do not reach the water table, are one technology that has been employed for recharge enhancement. All applications to-date, however, have focused on massive, large-diameter boreholes ranging from about 1’ (0.3m) in diameter upward and requiring significant installation logistics. We hypothesize that smaller installations, while capturing ambient stormwater runoff from low-contamination rural landscapes, can enhance groundwater recharge rates while protecting or enhancing local groundwater quality, and can be economically implemented in rural landscapes.