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Regulating Resilience: Climate-Water Dynamics in the Colorado River Basin

Natalya Holm and Logan St John


  • The Colorado River has been overallocated for a century due to the original Colorado River Compact promising more water than the river could actually deliver.
  • Incentives built into the prior appropriations doctrine, coupled with the impacts of climate change on the water resources of the Colorado River Basin, are exacerbating water shortages in the basin.
  • Alleviating water scarcity in the Colorado River Basin requires the combination of implementing scientifically supported conservation approaches and holistic management.
Regulating Resilience: Climate-Water Dynamics in the Colorado River Basin
Enrique R. Aguirre Ave via Getty Images

The Colorado River Basin is the largest and most crucial water resource in the American Southwest. The Colorado River provides drinking water to over 40 million people and irrigates approximately 5.7 million acres of agricultural land across seven states. However, water has been steadily disappearing from the Colorado River Basin over the last century. The consistent loss of Colorado River water became the subject of public concern in August 2021 when the Bureau of Reclamation declared the first ever water shortage on the Colorado River. This declaration was made following the Bureau’s projection that water levels on Lake Mead, the nation’s largest reservoir, would fall to 36 percent of the reservoir’s capacity by the end of 2021. Lake Mead water levels reached record lows in both 2021 and then again in 2022. Several factors have led to this regional water crisis that has nationwide consequences, including climate change and water regulatory frameworks in the west.

The Colorado River Compact

The Colorado River Compact is the oldest water allocation compact in the United States. Due to high water demand and limited water resources, an allocation strategy was necessary for the Colorado River to satisfy all water users. The result was the Colorado River Compact, an agreement for allocating the waters of the Colorado River signed among the states of Wyoming, Colorado, Utah, New Mexico, Nevada, and California in 1922, with Arizona joining in 1944. The Compact allocates 15 million acre-feet (MAF) per year from the Colorado River to the seven states based on a Bureau of Reclamation study that indicated the Colorado River’s annual discharge was 16.4 MAF. However, the annual discharge determination that the Compact is based on was made during one of the wettest periods in the American West. The Colorado River has not discharged 16.4 MAF since the Compact was signed. As a result, the Colorado River has been overallocated since its inception, promising more water than the river could deliver.

Colorado River Water Agencies

The Bureau of Reclamation is responsible for managing federal water and power projects on the Colorado River, including Hoover Dam and Glen Canyon Dam. The Bureau also helps basin states to identify and implement solutions to Colorado River water issues and facilitates the development of states’ water allocations.

Following the Compact’s allocation of 7.5 MAF annually to each of the Upper and Lower River Basins, it was the responsibility of the states within their respective basin to allocate that basin’s water amongst themselves. The Upper Basin states thus formed the Upper Colorado River Commission. The Lower Basin states required the intervention of the Supreme Court to determine water allocations, and the Bureau of Reclamation now acts as a custodian for the Lower Basin states and ensures each state receives their allocation.

Each Basin state has a state agency responsible for managing intrastate water resources, including Colorado River water allocations. However, local water districts and agencies that report to those state agencies are responsible for managing local water resources, diversions, and the provision of water to utilities and agriculture. These local water agencies are the entities that hold the water rights to Colorado River water and distribute it based on the prior appropriation doctrine.

Prior Appropriation Water Rights

The prior appropriation system allocates water rights based on the timing, place, and purpose of use. Water that is withdrawn must be put to a beneficial use. Beneficial uses are determined by the state, but could include agriculture, municipal water supply, recreation, industry, and mining, among others. The beneficial use of water is also not limited to within the watershed of the source water: water can be transferred outside the watershed to be put toward any beneficial use.

The prior appropriation system is based on priority, which is determined by when use of a water source began. A common saying used to describe prior appropriation is “first in time, first in right,” meaning that whoever puts water to a beneficial use first has the most senior rights to that water. The most senior appropriator has the highest priority and receives all their allotted water before all other junior appropriators in times of shortages. The prior appropriation rights system exacerbates the overallocation of the Colorado River by incentivizing farmers (who use 80 percent of the Colorado River’s water) to use as much water as possible to retain their water rights.

Climate and Water

Climate change is further exacerbating water scarcity in the Colorado River Basin. Climate and water are inextricably linked, and as the impacts of climate change worsen, its effects on the water cycle become more apparent. Climate change impacts precipitation patterns by causing increases in global temperatures, which results in greater evaporation rates, more frequent extreme heat events, drier soils, and decreased surface water flows. Studies have found that for each degree Celsius increase in temperature, the annual average discharge of the Colorado River has decreased by 9.3 percent, causing a loss of 10 trillion gallons of water from the Colorado River Basin. While droughts are historically common in the Southwest, climate change has intensified and lengthened droughts, placing more stress on water resources. In fact, the Southwest has been experiencing an exceptional “megadrought” since 2000 that is recognized as the driest period for the region in 1,200 years.

In addition to decreasing the volume of precipitation, increasing temperatures from climate change also affect whether precipitation falls as snow or rain. Mountain snowpack is a crucial source of water in the Colorado River Basin, historically acting as a natural reservoir that released a slow, consistent trickle of water to the headwaters of the Colorado River. Precipitation in the mountains now falls more often as rain with warmer year-round temperatures, reducing overall snowpack volumes. The warmer temperatures also cause the snowpack to melt earlier and faster, resulting in short, rapid flows through the Colorado River Basin’s streams that can disrupt existing hydropower infrastructure, negatively affect riparian ecosystems, and reduce water availability during the warmer season.

Climate change not only threatens the water quantity in the Colorado River Basin, but also water quality. Drier and warmer conditions increase adverse water quality impacts from wildfires and related activities as well as from harmful algae growth.

The Future of the Colorado River Basin

As less water flows through the Colorado River, Lower Basin states face even greater water cuts. Roughly 8 percent of Arizona’s annual water allocation was cut in 2021, while 21 percent of the water allocation was cut in 2023. More severe water cuts throughout the Basin are expected in the future. While many agree that action must be taken to conserve water and modify the Colorado River Compact, there are numerous obstacles. There is no end in sight for increasing temperatures and the megadrought conditions that are rapidly depleting water resources. On the regulatory side, the prior appropriation rights system encourages excessive water use while disincentivizing conservation. In addition, any changes to the Compact will require cooperation and agreement among the basin states on new allocation volumes. California, Arizona, and Nevada have taken small measures by signing agreements to temporarily reduce water consumption from the Colorado River, but there have been no permanent changes implemented in the Compact or state laws.

There is no single solution to suddenly produce enough water to satisfy all demand within the basin. Alleviating water scarcity requires the combination of implementing scientifically supported conservation approaches and holistic management. In agriculture, water efficient irrigation technology can reduce water consumption through techniques such as drip irrigation and alternative crop choice. Urban and industrial water conservation and circular solutions could also drastically reduce water demand in the Southwest. Pursuing clean energy supplies can reduce the demand for cooling water in thermoelectric powerplants. Nature-based solutions such as invasive species management and riparian ecosystem restoration would also save water while improving water quality.

All those strategies will require a regulatory paradigm shift––updating obsolete water laws and addressing deeply rooted water mismanagement strategies. The Bureau of Reclamation must define the healthy flow of the Colorado River that balances the health of the river system, well-being of basin residents, and economy of the region. This approach will inform the basin states’ collaborative planning, shifting the focus from using their full water allocations and creating new demand-driven diversions to sustainably using and conserving water resources. The Colorado Basin is in urgent and dire need of a systemic transformation of water management practices where science informs regulations. Successes achieved by piloting transformative water management in this basin could be applied to other critical basins in the Unites States and globally.