Keeping Water in Rivers

Advocating for Instream Flows

In Colorado, Western Resource Advocates is working to find smart, forward-thinking solutions that adapt to the changing needs of all who depend on rivers, including local communities, recreational boaters, farmers, ranchers, and fish and wildlife. We want to ensure the right amount of water is flowing through our rivers at the right moments, keeping in mind that everyone benefits when our rivers are healthy and flowing.

Why are instream flows important in Colorado?

Colorado’s local economies are more likely to thrive when streams are healthy and functioning. But climate change and drought are depleting Colorado’s rivers, and that is taking a toll on businesses, recreation, tourism, farmers, and wildlife. Add to that a history of outsized expectations of how much water rivers can provide, and Colorado’s rivers are getting more stressed, over-worked, and, in some cases, endangered.

One of the most promising ways to keep water in streams for the benefit of all is an “instream flow” water right. The state of Colorado, has been working to protect instream flows for almost 50 years.

What is an instream flow water right?

An instream flow water right is a water right secured to benefit the natural environment.

Typically, when we hear the term water right in Colorado, we think of a water user’s ability to take water out of a river, lake, or stream for consumptive use — such as for agriculture, domestic and commercial purposes, and in manufacturing. But there is another type of water right, called an instream flow water right. Instream flow water rights can only be used IN rivers, lakes and streams, so the water remains in the system and is available for downstream users.

Instream flow water rights in Colorado are secured exclusively by the Colorado Water Conservation Board (CWCB) with the sole purpose of preserving the natural environment. The CWCB also can acquire (through lease donation, or other means) other water rights to preserve or improve the environment. Since 1973, the CWCB’s instream flow program has helped protect more than 9,700 miles of stream and 480 natural lakes by appropriating water rights for instream use. It has also completed more than 35 voluntary water acquisitions, which provide flexible options for water right owners and the instream flow program.

What is consumptive vs. non-consumptive use?

Water use is divided into two broad categories: consumptive use and non-consumptive use. When water is consumptively used, it is removed from a river or other water body and used to meet an out-of-stream need, like irrigating pasture grass or providing drinking water to a city. When water is non-consumptively used, it stays in the river, e.g., for an environmental or recreational purpose, leaving water available for other downstream users.

How are instream flow water rights established in Colorado

There are few major river basins in Colorado that are not already over-allocated — meaning all of the water in the river is being used for a different use. So, where does the water come from to establish instream flow water rights?

There are two ways the CWCB can secure instream flow water rights:

  • it can appropriate water that is not currently part of another user’s water right (i.e. any water not currently in use on the stream), or
  • it can acquire water from another water user.
colorado river

New Appropriations

The CWCB receives recommendations for instream water rights for specific stretches of streams throughout Colorado. To make a claim for an instream flow, the CWCB has to ensure three things:

  • a natural environment exists at the proposed location,
  • there is water available to be protected in the river system, and
  • the instream water right will not cause harm to other water rights already established on the river.

Although instream flow water rights do not take water out of a stream, the priority order in which they are met within Colorado’s system of water managing water rights — a system often called “prior appropriation” — is treated as any other water right. So, when the CWCB protects a new instream flow water right, the water will only be left in the river or stream after all other “senior” water rights are met first.

Prior Appropriations

Prior appropriation is a water law system developed in the American West that establishes water rights based on the year in which a specific amount of water was first put to beneficial use (also known as “first-in-time, first-in-right”). The earlier the first beneficial use occurred, the more “senior” that water right becomes. During times of scarcity, “junior” water rights can be curtailed to ensure that “senior” water rights received their full allocations. In other words, the system dictates that the water use that began first is the first in line when there is not enough water to meet all of the established beneficial uses.

While the Instream Flow Program has been around since 1973, there are consumptive water rights in Colorado that date back a full century before, meaning instream flow water rights are relatively younger, or “junior,” to other water rights in the same river system. As a result, in dry years or years of heavy water use, instream flow water rights are often at risk of not being met, and are often left with insufficient water to protect the natural environment.


When the CWCB acquires an instream flow water right from another water use, the water will be left in the stream in whatever “priority” order the original water right was taken out of the stream. Acquisitions are a way that an instream flow can have seniority over other water rights already established in the same river system.

Acquisitions are especially important for another reason: acquisitions can be temporary, so can adjust to the needs of local water users and rivers.

Under the state’s current short-term loan program, the CWCB may accept temporary loans of water rights so that water stays in rivers if the State Engineer determines there will be no harm to the existing water rights of other water users. The approval process for these short-term loans can take less than two months and is relatively fast and affordable compared to other agreements, which may take years to settle in water court.

Due in part to this flexibility, Colorado’s instream flow loan program has begun to help solve some tricky water issues across the state. But the number of acquisitions is few and the loan program is limited by several constraints as to how often it can be done in a particular river reach. We believe these constraints should be eased to allow water users and the environment to reap additional benefits.

We have a lot of work to do to continue to protect our rivers in the West.

With a changing climate and more frequent drought, our communities need improved tools that provide us with the flexibility to meet more of the demands on our rivers, including protecting our natural environment. We need greater flexibility in how we manage our water resources so we can meet the ever-changing demands of rivers AND people. We need to proactively invest in our rivers and lakes today so we have clean, safe water in the future.

Important updates from WRA’s experts – straight to your inbox.

Western Resource Advocates