The Colorado River water crisis: Its origin and the future

Abstract

During much of the 21st century, natural runoff in the Colorado River basin has declined, while consumption has remained relatively constant, leading to historically low reservoir storage. Between January 2000 and April 2023, the amount of water stored in Lake Mead and Lake Powell, the two largest reservoirs in the United States, declined by 33.5 million acre feet (41.3 billion cubic meters). As of April 2023, total basin‐wide storage was sufficient to support the 21st century average rate of basin‐wide consumption for only 15 months. Runoff in spring 2023 is predicted to be large, providing a short‐term reprieve. However, it will take four to five additional unusually wet years in succession to refill Lake Powell and Lake Mead if basin‐wide water use remains unchanged. Increasing evapotranspiration and dry soils associated with global climate change makes such a scenario unlikely. To stabilize reservoir storage, basin‐wide use needs to equal modern runoff. To recover reservoir storage, basin‐wide use needs to decline even more. Based on 21st century average runoff, a 13%–20% decline in basin‐wide use would allow for stabilization and some reservoir storage recovery. Future policy debate about reservoir operations will inevitably concern whether most, or all, reservoir storage should be in Lake Mead or in Lake Powell. The choice of one or the other will result in significantly different environmental and recreational outcomes for Glen Canyon and the Grand Canyon.This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Human Water > Water Governance Science of Water > Water and Environmental Change

Institutional Dynamics Impact the Response of Urban Socio‐Hydrologic Systems to Supply Challenges

“…The uncertain future of Colorado River availability and the response of urban water systems to its basin-wide developments is a salient human-water systems challenge for us to illustrate the general operational and political-economic feedback dynamics in the UWIIM. Multiple scholars (Fleck & Castle, 2022;Schmidt et al, 2023;Wheeler et al, 2022), the Bureau of Reclamation (DOI, 2022), and water users (Goddard & Atkins, 2022), argue that the existing water distribution rules are not enough to address the Colorado River's pressing state, which may require a 2-4 MAFY basin-wide cut in use (DOI, 2022). The Bureau has undergone a Supplemental Environmental Impact Statement process to reform the 2007 guidelines (Bureau of Reclamation, 2022) and published a draft (D-SEIS) in April (Bureau of Reclamation, 2023b) that includes two alternatives to share needed cuts by the traditional priority system or adopt a use-proportional sharing approach.…”

Quantifying the contributions of tributaries to large‐river fish populations through mark‐recapture modeling

“…In the Grand Canyon, Colorado River regulation and hypolimnetic discharge from Glen Canyon Dam caused the conversion of seasonally-varying water temperatures to colder and thermally-stable temperatures that limited spawning and rearing of warmwater spawning large-river fishes (Robinson et al 1998;Coggins et al 2006;reviewed in Melis 2011). In recent years, however, basin-wide declines in Colorado River reservoir storage have increased the potential for invasion of warmwater sport fishes through increased entrainment and passage through Glen Canyon Dam (Schmidt et al 2023). The continued decline in water storage in Lake Powell, upstream of the Grand Canyon, is predicted to lead to conversion of main-stem native fish populations to an introduced warmwater fish assemblage (Dibble et al 2021;Bruckerhoff et al 2022).…”

“…Recent invasions of warmwater predatory fishes into the Grand Canyon facilitated by drought and declining reservoir levels (Dibble et al 2021;Schmidt et al 2023) may intensify the focus on isolated tributaries in providing protective rearing habitat and refuge populations for Humpback Chub and other native fishes (Bouska et al 2023). Tributary habitats and populations can sometimes be purposely isolated above barriers to protect populations from downstream invaders (Fausch et al 2009).…”

Translocation in a fragmented river provides demographic benefits for imperiled fishes

“…Complex interactions between water overallocation, construction of dams and diversions, lotic to lentic habitat conversion, and megadrought are playing out in the western United States, with severe consequences for native fishes (Gido et al, 2023; Pennock et al, 2022; Schmidt et al, 2023). The Colorado River basin, in the southwestern United States, is one of the most heavily managed river ecosystems in the world, with the entire flow diverted for consumptive use (Wheeler et al, 2022).…”