A major water crisis has emerged over the southwest US since the early 2000s due to low precipitation totals and high temperatures resulting in what is often referred to as a “megadrought” (Williams et al, 2020; Udall and Overpeck, 2017). Tree ring analyses have demonstrated that 2000-2021 was the driest 22-year period in over one thousand years, in part due to anthropogenic climate change (Marvel et al., 2019; Williams et al., 2020, 2022). 

This ongoing drought has impacted the reliability of the Colorado River system to meet water allocation agreements and hydroelectric power generation targets.  Future rising temperatures and shifting precipitation from snow to rain could make streamflow harder to predict and water resources less reliable, and any precipitation increases that might occur, are likely offset by the impacts of warming temperatures (Siirila-Woodburn et al., 2021). 

The HyperFACETs Megadrought Storyline group is investigating many stakeholder relevant aspects of the southwest US Megadrought.  This includes working to develop skillful multi-year hydroclimate predictions for the region, evaluating long-term projections of water resources in the region, and exploring which adaptive measures (e.g. reservoir operations, water transfers, water conservation methods) might ameliorate the impacts of future drought. 

In this work we utilize the IM3/HyperFACETs Thermodynamic Global Warming (TGW) Simulations (Jones et al, 2023) to study the the potential impact of climate change on the intensity and spatial extent of drought in the southwest U.S. and over the Colorado River Basin.  Drought metrics including SPI, SPEI, and soil moisture anomalies are explored in this study.  The unique aspect of the TGW simulations over other pseudo global warming scenarios is that these runs allow for the exploration of uncertainty by including multiple time horizons (mid and late century) and multiple temperature and humidity change combinations. Results will examine the entire 2000-2019 drought period.  The goal is to eventually run these simulations and through hydrologic impacts models to understand the potential impact warming could have on water resources in the west.