A Colorado River report card
Lake Mead Water Year 2023, based on the most recent Bureau of Reclamation 24-month study
| Lake Mead | million acre feet | percent full |
| Start of WY2023 | 7.328 | 28.08% |
| End of WY2023 | 6.508 | 24.93% |
| gain(loss) | (0.820) | -3.14% |
Current forecast U.S. Lower Basin water use
| state | projected use in maf | percent of full allocation |
| California | 4.427 | 100.61% |
| Arizona | 2.36 | 84.29% |
| Nevada | 0.227 | 75.67% |
Sources: Projected reservoir levels, February 24-month study, retrieved March 13, 20-23; Forecast Lower Basin use, USBR Forecast, March 10,2023, retrieved March 13, 2023
Some “inconvenient science”
An Assessment of Potential Severed Droughts in the Colorado River Basin
Salehabadi, Homa, et al. “An Assessment of Potential Severe Droughts in the Colorado River Basin.” JAWRA Journal of the American Water Resources Association (2022). (from the terrifically helpful Utah State Colorado River team and collaborators)
We summarize our updated understanding of plausible future drought conditions by considering historical flows, tree-ring reconstructions, and climate change…. We produced three drought scenarios, each comprising 100 streamflow sequences to be used as input to systems operation and management models. We used analysis of the duration-severity and cumulative deficit relative to the mean natural flow to evaluate droughts and drought simulations and show that the current millennium drought that started in 2000 has an average flow far less than the historical record. However, the flows reconstructed from tree rings or future flows projected from climate models indicate that even more severe droughts are possible. When used as input to the Colorado River Simulation System the drought scenarios developed indicate considerable periods when Lake Powell falls below its hydropower penstocks, indicating a need to rethink management and operation of these reservoirs during these critical conditions. (emphasis added)
Let the rethinking begin.