The Colorado River Basin (Figure 1) covers more than 246,000 square miles in seven U.S. states and Mexico. Basin waters are managed and governed by multiple laws, court decisions, and other documents known collectively as the Law of the River. The Colorado River Compact of 1922 established a framework to apportion water supplies between the river’s Upper and Lower Basins (divided at Lee Ferry,AZ). Each basin was allocated 7.5 million acre-feet (MAF) annually under the compact; an additional 1.5 MAF in annual flows was made available to Mexico under a 1944 treaty. Since the Upper Basin’s waters were developed after much of the Lower Basin, its apportionments are significantly less than the full amount allowed under the compact and are framed mostly in terms of percentages of available supplies. The Bureau of Reclamation (Reclamation) plays a prominent role in basin water management due to the many federally authorized projects in the basin.
Credit: The Congressional Research Service
The Colorado River Basin is in the midst of a long-term drought, during which consumptive use has regularly exceeded natural flows. When federal and state governments originally approved the 1922
compact, it was assumed based on the historical record that river flows would average 16.4 MAF per year.
Actual flows from 1906 to 2020 were approximately 13.9 MAF, with flows averaging approximately 12.5 MAF since the onset of the basin’s drought in 2000. These conditions are projected to continue.
Observers track the status of two large federal reservoirs—Lake Powell in the Upper Basin, impounded by Glen Canyon Dam, and Lake Mead in the Lower Basin, impounded by Hoover Dam—as an indicator of basin storage conditions. Reclamation makes operational decisions for basin reservoirs in monthly 24-month studies. Recent 24-month studies projected additional reductions in water storage at both reservoirs (Figure 2, Figure 3).
Credit: USBRCredit: USBR
Mitigating Drought in the Colorado River Basin Previously, there have been multiple efforts to improve the basin’s water supply outlook, including the 2003 Quantitative Settlement Agreement, the 2007 Interim Shortage Guidelines, and the 2019 drought contingency plans (DCPs) for the Upper and Lower Colorado River Basins. (The latter were authorized by Congress in P.L. 116-14.) The DCPs required reduced Lower Basin deliveries based on Lake Mead storage levels, authorized additional water conservation efforts, and put in place the framework for a Drought Response Operations Agreement (DROA) to coordinate Upper Basin operations to prevent the loss of hydropower generation at Glen Canyon Dam.
Despite these efforts, storage levels at both reservoirs have continued to fall. In August 2021, Reclamation declared the first-ever Level One Shortage Condition for the Lower Basin, which formally triggered delivery curtailments for Arizona (512,000 AF) and Nevada (21,000 AF). Reclamation’s August 2021 24-month study also indicated for the first time the possibility of Lake Mead falling below 1,020 feet within two years, which resulted in agreement on a new set of actions in 2021, known as the 500+ Plan. This effort is expected to result in the conservation of an additional 500,000 AF in Lake Mead in 2022 and
2023 (i.e., 1 MAF total).
In March 2022, Lake Powell fell below 3,525 feet for the first time since the late 1960s. To alleviate the potential for lost hydropower generation at Glen Canyon Dam, the Department of the Interior initiated DROA operations, resulting in operational changes in July 2021 and January 2022. In May 2022, Reclamation invoked emergency authority to move approximately 500,000 AF of water from Flaming Gorge Reservoir to Lake Powell and held back 480,000 AF of Lower Basin releases pursuant to the 2007 guidelines.
At a June 14, 2022, congressional hearing, Reclamation announced that states needed to conserve an additional 2 MAF to 4 MAF in 2023 to protect storage volumes over the near term (2023-2026). This estimate was the result of a 2022 Reclamation analysis. Reclamation noted that if the target is not met with voluntary commitments by August 2022, the agency would act unilaterally. In a July 18, 2022, letter to Reclamation, Upper Basin representatives declined to contribute a specific volume of cutbacks to these
efforts, instead laying out a five-point plan as the basis for its water conservation efforts.
Congress is involved in basin management primarily through directives and authorizations for Reclamation projects and activities. In addition to the 2019 authorization of the DCPs, Congress has authorized “system conservation” efforts in the basin that expire in 2022. Congress also has appropriated regular and supplemental appropriations for Colorado River water conservation efforts in addition to regular operational funds. Legislation under consideration in the 117th Congress would enact other new authorities aimed at improving basin water management.
The 2007 Interim Shortage Guidelines and the 2019 DCPs are set to expire at the end of 2026. Extending or amending previous agreements is central to future basin water management. On June 20, 2022, Reclamation published a “pre-scoping” notice seeking input on how to foster participation in the National Environmental Policy Act (NEPA) process to develop post-2026 basin operations. A formal notice for NEPA scoping is expected in 2023.
Author Information Charles V. Stern
Specialist in Natural Resources Policy
Unfortunately, the situation on the Colorado River is not unique. Colorado’s mountains are the headwaters of four major river systems: the Colorado, the Platte, the Arkansas and the Rio Grande. Each river provides critical water supplies for the present and future needs of our state; each is being impacted by the effects of climate change; and under Interstate water compacts signed decades ago, Colorado must share each with its neighboring downstream states. Climate change, or what scientists are now referring to as aridification, has caused all of Colorado to be hotter and drier. The combined effects of climate change, interstate water compact obligations and intense competition for the available water among different communities and water use sectors within our state means that future Coloradans will have to learn to do more with less water. This will take bold action, compromise and a new era of innovation and cooperation among competing water interests within Colorado and among Colorado and its neighboring states.
Rio Grande through the eastern edge of Alamosa July 5, 2022. Photo credit: Chris Lopez/Alamosa Citizen
Already, the farmers in Colorado’s fertile Rio Grande Basin are struggling to maintain an aquifer by restricting pumping. They face an awful choice — reduce their collective uses of the aquifer to a sustainable level so that some farms can survive, or they all fail. At the same time, the surface water supply from the Rio Grande River, which must be shared with New Mexico and Texas, has diminished and most likely will continue to do so.
The Republican River’s South Fork near Hale, Colorado, with the region’s seemingly endless fields. Credit: Wikimedia Commons/Jeffrey Beall
The Republican River Basin, a small but agriculturally important river system that originates on the plains and flows east to its confluence with the Missouri River, is also stressed by overuse of the river supply. Productive farm fields are being fallowed so that Colorado can comply with the Republican River Compact. Fortunately for the Rio Grande and Republican river basins, the General Assembly set aside $60 million to buy out farms in order to leave water in the aquifers and river systems. That amount is a drop in the bucket for what will be needed to recover and sustain those systems.
Photo shows Tennessee Creek near the confluence of the East Fork Arkansas River in winter with snow on the Continental Divide of the Americas. The report evaluates current and emerging snow measurement technologies for the Western United States. Photo: Reclamation
The South Platte River runs near a farm in Henderson, Colorado, northeast of Denver. Henderson is the site of one of the possible reservoirs for the regional water project proposed by SPROWG. Photo credit: Lindsay Fendt/Aspen Journalism
The Arkansas River and South Platte River systems also have significant challenges. These basins are home to 85% of Colorado’s population and to most of its commercial agriculture. The farm economy in the Arkansas has already suffered when the Colorado State Engineer had to cut back the use of alluvial wells, which were depleting flows to the Arkansas River and causing Colorado to be out of compliance with the Arkansas River Compact. The South Platte River system, which relies on return flows to sustain the river past the state line, is seeing much higher demands. The current return flow regime is threatened by Nebraska reinvigorating the proposed Perkin’s Ditch, a century-old feature provided for in the 1923 South Platte Compact. Both these basins are being hammered by the combined impacts of Front Range cities rushing to buy and dry existing farms to provide water for future growth while their water supplies imported from the Colorado River Basin have become less reliable due to climate change caused drought and compact obligations.
Colorado’s future economy will depend on implementing innovative methods to sustain, deliver and treat water supplies while leaving enough water in our streams to maintain healthy and thriving aquatic ecosystems. Water delivery entities need to think broader to collaborate with others on ways to manage and share their supplies and their systems.
