By Jack Schmidt | February 12, 2024 (cross-posted from the Center for Colorado River Studies)

Nothing really changed in Colorado River Basin reservoir storage during January 2024. That is really good news as the basin prepares for the upcoming irrigation season.

1. Total basin water storage did not significantly change during January 2024 (Fig. 1, blue line). In fact, total basin storage increased a tiny bit—34,000 af (acre feet)—and was 28.0 million af on 31 January. Conditions in the basin remain comparable to conditions in spring 2021. There is no reason so stop our efforts to conserve reservoir storage!

Figure 1. Graph showing total basin storage in 46 reservoirs in the Colorado River basin between 1 January 2021 and 31 January 2024 (blue line). The black arrow points to the previous time when reservoir storage was at this amount. Total storage in Lake Mead and Lake Powell for the same period is shown by the orange line. Compiled from data downloaded at https://www.usbr.gov/uc/water/hydrodata/reservoir_data/site_map.html

2. Although the total storage has not changed, storage in specific reservoirs has been adjusted. Storage in CRSP reservoirs upstream from Lake Powell, including Fontenelle (Fig 2, green line) decreased by 109,000 af and has been decreasing since mid-summer 2023. Storage in Lake Powell (Fig. 2, gold line) decreased by 303,000 af. There was no significant change in storage in other Upper Basin reservoirs (Fig. 2., black line). In contrast, storage in Lake Mead (Fig. 2, purple line) increased by 368,000 af. On 31 January, active storage in Lake Mead exceeded active storage in Lake Powell by 1.27 maf; Lake Mead held 9.41 million af and Lake Powell held 8.14 million af. Storage in Lake Mead has slowly been increasing since mid-summer 2022.

Figure 2. Graph showing active reservoir storage in different parts of the Colorado River basin between 1 January 2021 and 31 January 2024. The category “other Upper Basin reservoirs” includes Granby, Dillon, McPhee, Strawberry, Starvation, Nighthorse, and 30 others. The category “CRSP reservoirs upstream from Lake Powell, and Fontenelle” includes Blue Mesa, Morrow Point, Crystal, Fontenelle, Flaming Gorge, and Navajo.

3. Basin reservoir storage continues to be depleted at an unprecedented low rate in comparison to the past decade (Fig. 3), as is also the case for the combined storage of Lake Mead and Lake Powell (Fig. 4). On 31 January 2024, the amount of basin storage gained by the 2023 snowmelt runoff had been reduced by 20%.

Figure 3. Graph showing the rate of reduction in basin-wide reservoir storage in each of the past ten years. The reduction in storage in 2023/2024 has been at a much slower rate than in other years. Each year that plots lower than 2023 (blue line) on this graph reflects a higher rate of loss in storage than the current year.

Figure 4. Graph showing the rate of reduction in the combined storage in Lake Mead and Lake Powell in each of the past ten years. The reduction in storage in 2023/24 has been slower than in any other recent year. Every year plots lower than 2023 (blue line) reflecting a higher rate of loss in storage than in this year.