There have been growing concerns about water security in the southwestern US because of dwindling supplies and rising demands. The hydrology of the region is changing in ways that could critically undermine water supplies, agricultural production, power generation, and river-dependent ecosystems. Of particular concern is the declining flows in the Colorado River, a lifeblood for over 40 million people in seven southwestern states. Frequent and prolonged droughts have brought reservoir water levels in the Colorado River to record lows, raising concerns about a water crisis if current trends continue. This project examines whether future water demands in the southwestern US can be met under projected future conditions and current water management practices while maintaining environmental flow requirements, and if not, whether there are alternative approaches to achieving sustainability. The project directly engages regional stakeholders for participation in co-producing key aspects of the research and ensuring deliverables that are of the greatest value for improved water resource management. It also provides exposure to K-12 and undergraduate students regarding one of the nation’s most pressing water resource sustainability issues.

The project uses high-resolution, long-term hydrologic simulations from a state-of-the-art hydrological modeling system to systematically examine the complex interplay between decreased water supplies, future demands, and the role of water management (e.g., reservoir operation, groundwater use, and out of basin water transfer) in building resilience. The specific project objectives are to (1) quantify the future changes in water supplies and demands and examine their spatio-temporal trends and variabilities, (2) examine the changes in surface reservoir and groundwater storages, and quantify risks of storage depletion associated with intensified future droughts, and (3) co-develop potential pathways with regional stakeholders by considering tradeoffs between competing inter-sectoral water use and environmental flow requirements, and evaluate these pathways under a range of scenarios. By considering various weather and water use scenarios, combined with stakeholder-informed management options, the project holistically examines various possible pathways for water resource resilience in the southwestern US. The modeling framework developed in this project will provide major advances in the ability to simulate coupled natural-human systems in highly water-scarce regions. Project outcomes will be used in informing water resource management and educating K-12 and college students on growing water scarcity issues.