REGIONAL SCALE WATER AVAILABILITY ASSESSMENT IN THE UPPER COLORADO RIVER BASIN

The lack of comprehensive water supply prediction capacity poses challenges in evaluating water availability. In order to improve water availability prediction and assessment, in 2019, the U.S. Geological Survey initiated planning efforts to intensively study ten medium-sized basins throughout the U.S. over the next decade, including the Upper Colorado River Basin (UCOL). Extensive data collection, analysis, and modeling activities in the UCOL, and other basins, are directed toward, and culminate in, integrated regional assessment of selected facets of water availability. The regional water availability assessments will seek to understand how water supply and demand vary over space and time, identify the factors driving variability, and assess the vulnerability and resilience of human populations and ecosystems to water shortages, surpluses, and degradation of water quality. To ensure that regional water availability assessments both inform national assessments and address regionally important science questions, scientists in each basin will evaluate (1) consistent water quantity, quality, and use indicators and (2) basin-specific science topics. The basin-specific study in the UCOL aims to provide insight into how past, present, and future snow conditions – including amount, timing, melt, and transitions from snow- to rain-dominated systems – impact water supply and quality and the ability to meet demand. A coupled groundwater-surface water hydrologic model (GSFLOW) and a temporally dynamic salinity model (SPARROW) are being applied to meet this objective. These tools, as well as other data and research, support the development of an integrated modeling system that will allow for an examination of water availability and sustainable water management that considers the combined effects of changing climate, drought, land use/cover, water use/demand, and other socioeconomic factors.