Abstract
<jats:p>Clean, reliable water is critical for drinking, the production of water-intensive commodities, and maintaining healthy ecosystems and economies. Upstream hinterlands play an outsized role in providing vital water resources to downstream cities, primary centers of economic productivity, prosperity, and population. With unprecedented pressure on water resources from climate change, population growth, water use, extraction, and pollution, there is a critical need to understand the dependence of downstream regions on upstream watersheds that provide freshwater. Previous studies have substantiated upstream-downstream dependencies at global-, continental-, and regional-scales, which are often too coarse for basin-scale decision-making. Here we present a basin-scale water tower model that quantifies upstream-downstream dependence at high resolution (~800 m & ~4.7 km) by spatially connecting downstream water users to upstream locations of runoff generation. This study investigates the Potomac River Basin, which provides ~75% of total surface water for the Washington, D.C. metropolitan area. Recent research suggests near-future instances of water scarcity across the basin due to population growth, increased sectoral water demand, and climate-driven increases in atmospheric demand. We present a basin-scale water tower framework that identifies explicit locations in the watershed that play disproportionately large roles in supplying freshwater to the D.C. metropolitan area, highlighting the region’s dependence on the rural hinterlands. This research provides an innovative approach for targeted conservation efforts across the region to enhance sustainable water resources management and water security.</jats:p>