ENHANCING AQUIFER RECHARGE ON PUBLIC LANDS OF THE COLORADO PLATEAU TO ADAPT WATER SUPPLIES FOR CLIMATE AND LANDSCAPE CHANGE

Arizona is starting a new initiative to identify timing and locations favorable for managed aquifer recharge (MAR) across the entire state. This presentation focuses on implementing this project across public lands on the southern Colorado Plateau, a high-elevation region increasingly vulnerable to declines in snowpack duration. Recent climate models predict hotter and drier conditions on the Colorado Plateau leading to extreme droughts and a transition from snow-driven to rain-driven recharge. The resulting decline in snowpack duration will lead to water level declines in historically water-stressed aquifers in arid regions. Often catchment-scale or smaller, current MAR practices entail effective enhancement of groundwater recharge. In the larger-scale, improved forest and land management practices have the potential to improve recharge.

This study uses data from existing instrumented streams, springs, and wells in federally, state, and city managed land across the southern Colorado Plateau. Sites at a gradient of elevations help determine orographic influences on aquifer recharge. We use daily and sub-daily runoff data to estimate natural recharge volume, runoff values, and baseflow contributions. We use baseflow change to determine the effects of climate and land use on recharge. Remote sensing measurements of snow cover and duration coupled with topographic data allow us to characterize the locations and timing of recharge to identify areas conducive to rapid recharge. Analyses of sites in Grand Canyon National Park, Coconino National Forest, and Navajo Nation allow for transparency of water availability in a variety of publicly managed lands.

We utilized baseflow separation, land cover distribution, and topographical analyses to locate areas suitable to enhance aquifer recharge of unallocated water. Much of the geology of the Colorado Plateau is defined as karstic, necessitating detailed mapping of surficial features and local hydrogeology to locate appropriate areas for enhanced recharge. Locations for MAR are dependent on finding suitable karst geomorphology that intersect with local needs. These analyses allow for an empirical understanding of current and potential runoff volumes available for recharge and suggestions can be provided to policymakers for future MAR implementation.