Colorado’s West Slope Basins Could Face Mid-Century Tipping Point of Drought Vulnerability
Recent drought has severely affected Lake Powell, and Colorado’s West Slope basins’ ability to maintain water deliveries to Lake Powell is at risk.
Water from Colorado’s West Slope basins is critical for the economy and environment across seven western U.S. states. It is crucial to understand the likelihood and severity of future droughts in these basins. Traditional planning approaches rely on the historical record to understand future risks. However, the historical record does not necessarily tell the whole story of the potential for drought, and climate change is expected to make things worse. Using a new modeling approach, we show that future extreme drought could become more common, with unprecedented impacts on water supply for agriculture, hydropower, and the environment. Our research helps water managers better understand the risks and plan for these changes.
This research is crucial because it addresses the growing challenge of managing water resources in Colorado's West Slope basins, which are vital for the Colorado River and local communities. It is the most advanced study of the potential for drought in the region to date, using an innovative modeling approach to simulate thousands of possible pathways of water supply based on historical and future climate. The model helps us understand that worse droughts are possible even if the climate does not change, and that climate change could make droughts even more severe and frequent. This research provides a framework for other scientists studying drought in complex multi-basin regions and emphasizes the need for water management to plan for changes in drought frequency and severity.
We explore the multi-sectoral drought vulnerabilities in Colorado's West Slope River Basins, a critical water source for the Colorado River and Lake Powell. Our research introduces a novel multi-site Hidden Markov Model (HMM) to generate synthetic streamflows that better capture the region's drought extremes. By perturbing the HMM, we simulate future climate changes and then route both sets of streamflows through StateMod, Colorado's water allocation model to evaluate drought impacts. Our findings reveal that accounting for internal variability alone can lead to drought conditions exceeding historical extremes, significantly affecting local water uses and deliveries to Lake Powell. And even modest climate change projections indicate a shift to a drier regime, where historically low delivery volumes and extreme drought impacts become routine. These insights are crucial for future Colorado River planning and can be applied to other snow-dominated regions facing persistent droughts.
Our study highlights the severe strain on the West Slope Basins from droughts driven by both internal variability and climate change. The results underscore the urgent need for innovative water management strategies to mitigate the multi-sectoral impacts of droughts, including changes in water allocation and reservoir operations, to sustain agricultural output, reservoir levels, and sensitive ecosystems.