Climate Change, Development, and Groundwater-Surface Water Interactions in Grand Canyon National Park

Abstract: Groundwater has played a significant role in shaping the Grand Canyon and sustaining diverse and often rare flora and fauna over time. The paucity of studies on the recharge behavior and flowpaths for the springs on the North and South Rim is a testament to the difficulty in accessing and monitoring springs and seeps in the canyon. That being said, the combination of modeling and hydrochemistry work has shown that the groundwater system feeding the North Rim springs is fed locally by monsoonal precipitation and has relatively short residence times of days to months owing to the fractured, karstified nature of the Kaibab and Redwall-Muav Limestones. The South Rim springs are part of a regionally extensive groundwater system that likely receives most of its recharge in the mountains near Flagstaff, with longer residence times of up to thousands of years and consequently higher salinities. Climate change threatens water supply in the region with diminishing snowpack and extended droughts forecasted for the Western US, and proposed development such as in Tusayan and The Grand Canyon Escalade may result in additional demand on groundwater for water supply. This combined with a projected doubling of annual visitors to the Park presents a serious challenge for water managers, in balancing demand with the environmental (and tribal) impacts of decreased springflow for the national park. Future solutions that avoid drilling wells on the Coconino Plateau may require the importation of Colorado River water, but by far the most politically and economically feasible measure lies in demand-side strategies such as water recycling, stormwater capture, and irrigation efficiency measures.