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Weekend Getaways

Upper Colorado River Basin Compact of 1948

The Colorado River watershed is divided into an upper basin and a lower basin and includes seven states. The Upper Basin includes parts of the states of Colorado, New Mexico, Utah, Wyoming and Arizona. What is the 1948 Upper Colorado River Basin Compact and why is it important?

The Colorado River is an important resource for the United States and Mexico. It supplies around 40 million people in both countries with water, 70 percent of which is used for agriculture. Because it is such a valuable resource in a dry part of North America, strict rules must be in place to ensure water is properly allocated.

What is the 1948 Upper Colorado River Basin Compact? Why is it important? We’ll take a look at it now.

What is the 1948 Upper Colorado River Basin Compact?

The Colorado River Compact is an agreement between Upper Basin states on how much water they can withhold from the Colorado River. Also formed was the Upper Colorado River Commission, which continues to oversee water collected in the Upper Basin and channeled to the Lower Basin states. This contract was drawn up on October 11, 1948.

Certain percentages of water remaining after lower basin mapping are specified in the Upper Colorado River Basin Compact. The upper basin states were promised the following percentages of remaining water:

  1. Wyoming: 14%
  2. Colorado: 51.75%
  3. Utah: 23%
  4. New Mexico: 11.25%

Since the Upper Basin supplies ninety percent of the Colorado River’s water, in extenuating circumstances these states must consider the needs of their downstream neighbors. Drought conditions are an example of such a circumstance. If, in turn, the Upper Basin cannot provide the necessary water resources without affecting its condition, the new commission is expected to work on an intergovernmental solution.

The Colorado River Compact is an agreement between Upper Basin states on how much water they can withhold from the Colorado River.

©Ken Lund / Flickr – License

Why is the 1948 Upper Colorado River Basin Compact important?

The 1948 Colorado River Basin Compact was important because it determined how much water the upper basin states would retain while meeting the needs of the lower basin states. This was critical to prevent fast-growing states from hogging all the water before other states could develop. The amount of water to which the Lower Basin states are entitled is specified in the 1922 Colorado River Compact.

Lower Basin states include California, much of Arizona, and Nevada. The water from the lower basin also supplies Mexico with its ration. The upper basin states retain a certain percentage of the remaining water per state after the lower basin allocation as a result of the 1948 Pact.

There were concerns that the needs of the lower basin states could affect the current and future needs of the upper basin states. The commissions and agreements established in the 1948 Colorado River Basin Compact reserve sufficient water for agricultural and industrial growth in the Upper Basin. This pact also addresses water distribution from some of the basin’s smaller tributaries that are shared by the states.

The Colorado River Basin Compact also addresses tribal water rights for the first time, though not extensively. It imposes a duty on the states where the land is located to provide indigenous communities with adequate water resources.

How does the Upper River Basin Compact affect dams?

When a dam blocks river water in a state, the water that dam contains comes from the total allotment for that state. This feature in the Upper River Basin Compact has been instrumental in preventing states from unfairly hoarding water resources.

Water may be held for hydroelectric purposes by certain states. Just because the water is being held back doesn’t mean that the said state-owned power producer doesn’t have to deliver equivalent amounts of water downstream. This mindset was built upon and enshrined in law in the Colorado River Storage Project Act of 1956.

1669127027 471 Upper Colorado River Basin Compact of 1948 - October 1, 2023
The Hoover Dam provides hydroelectric power and irrigation water for much of the Southwest United States.

©Matej Hudovernik/

What is the law of the river?

The Law of the River is a collection of statutes, treaties, agreements, regulations, and other treaties that dictate certain water rights to each state that depends on the Colorado River. The upper basin states are specially regulated so that the lower basin states receive promised amounts of water.

The river law as a whole is designed to ensure that the interests of all seven states along the river are equally considered. It preserves the rights of the upper basin, where most of the river’s water is generated. The greatest need is in the Lower Basin, which is also guaranteed a certain amount of water.

Unfortunately, the current water allocations of today’s river law are stretching water resources. On average, the river has insufficient water to meet the needs of the seven affected states.

This leads to legal problems and water crises, which are exacerbated by prolonged drought. The Upper Basin is no longer generating as much excess water as in the past. Development in these upper basin states has tied up more legally promised water resources, leading to severe water shortages downstream.

Lake Powell and Lake Mead are dangerously low, although drastic decisions have not yet been forced by this unfolding crisis.

Lake Powell Reservoir on the Colorado River.
Lake Powell, a large reservoir on the Colorado River, is experiencing drastically low water levels due to drought and increased water use.


Why is Lee Ferry in Arizona important to the Law of the River?

Lee Ferry, AZ is important to the Law of the River as it is the dividing point between the upper and lower basins. It is near the Utah-Arizona border. It is also the point at which water levels are recorded to ensure that lower basin states receive the promised amounts of water.

Water levels and flows are recorded by a stream meter, which has provided the most detailed records of water flow in the United States. Power meters record data every 15 minutes for the US Geological Survey to interpret. This allows them to monitor the ever-changing river water and determine exactly how it flows and how high it is.

This site was chosen because it was historically used as a river crossing for the Colorado River. It is one of the few points near the middle of the river that is easily accessible from either side.


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