Water 101

Colorado Water Law

The principle governing Colorado water use comes down to what’s commonly called “first in time, first in right,” or prior appropriation. The system arose during settlement and the Gold Rush, promising people who put water to “beneficial use” — mining, farming, raising livestock or supplying communities — that if new users moved in, their water couldn’t be cut off. That water right is considered a legal property right to use a maximum amount of a public resource, whether surface or groundwater.

In times of short supply, court-decreed water rights with earlier dates (senior rights) can use water before rights with later dates (junior rights). The Colorado Division of Water Resources (DWR) administers water rights — satisfying senior users first and, where necessary, curtail- ing junior or undecreed uses. Since 1879, disputes about water right priority dates and amounts have been settled by Colorado water courts. There are seven water divisions in Colorado, based on the state’s watersheds, with a water court and a DWR division engineer in each.

Through water court, water rights can also change locations and types of use as long as that change will not “injure” water rights held by others. Injury to water rights occurs when an action may cause a water right holder to lose water in the amount, time or place they’re entitled to use it. The law also allows for water rights to be abandoned. So, if a water right is not being used, it is subject to consideration for abandonment.

Over the decades, state lawmakers have officially recognized new “beneficial uses,” including in-channel water for recreation and instream flows for the environment. Only the Colorado Water Conservation Board can hold rights for instream flows, and only government entities can hold recreational diversion rights. Across Colorado, 28 riverside communities have secured at least conditional water rights for flows that allow for recreation, often accompanying a whitewater park. In 2022, after nine years of work, Glenwood Springs was awarded Colorado’s most recent recreational in-channel diversion to construct a boating park.

Where Your Water Comes From 

Water loops through the world in a cycle likely familiar from a grade school science lesson: Transpiration from trees and evaporation from surface water rises and condenses into clouds, producing precipitation. Precipitation accumulates into snowpack, then melts into streams, rivers and aquifers. Surface water is positioned to evaporate and be released into the sky again. What people might forget is that it’s a closed cycle: “The amount of water is the same, always, it just moves to different places,” says Melissa Clutter, an assistant professor of geosciences at Fort Lewis College.

In Colorado, the amount of water available is rarely enough to meet all demands. The Colorado Water Plan provides a framework for helping Coloradans meet water challenges. According to the water plan, Colorado communities could need 230,000-740,000 acre-feet of additional water per year by 2050.

As water flows downstream, it carries sediment, nutrients, pollutants and other debris, which can affect water quality. A watershed is defined by an area of land where water flows through a network of drainages to a collection point like a stream, river or lake, which pools the water and everything it carries.

That means the health of forests matters to everyone downstream. As Jonathan Paklaian, executive director of the Arkansas River Watershed Collaborative puts it, “Our forest health is also our watershed health.”

Any problems for the forests, like wildfires and insect infestations that change how a forest stores snow and how water runs off become problems for water supply and quality. Making a difference for water means thinking on the scale that it flows — far downstream and across jurisdictions.

In a healthy watershed, water soaks into the ground and moves slowly through it or, in the case of snow, melts gradually out from under a thick canopy of trees. But when trees die or are burned in a wildfire, water and snow wash off quickly. Erosion cuts into more soil, and sediment washes downstream, along with wildfire ash and debris, which can clog infrastructure and pollute the water supply.

A history of suppressing wildfire has left forests thick with “fuels.” Add climate change’s warmer and drier weather, and the results are bigger, more frequent fires. Now the race is on to protect forests — and water — from catastrophic wildfire.

Source water protection now ranks as the top concern for water professionals, according to the American Water Works Association’s 2024 State of the Water Industry Report. This year, that issue surpassed concern about aging infrastructure for the first time in the report’s 20-year history.

“If we don’t have safe and reliable sources, we don’t have the ability to support public health,” Raven Lawson, AWWA Source Water Protection Committee chair, said in a press release about the report. About 60% of water utilities are implementing or creating source water protection plans according to the survey.

The Colorado Water Conservation Board’s (CWCB) Wildfire Ready Watersheds program is helping communities plan for wildfire and take measures to mitigate before they begin. Through the program, communities can receive grant funding to craft a Wildfire Ready Action Plan. Plans incorporate local data and values in order to identify and rank risks.

Compacts

Turn on the tap, and the water flows. Little about that reliable delivery betrays the interconnected systems at play. As Jason Ullmann, Colorado’s State Engineer sees it, interstate and international agreements with 18 downriver states and Mexico govern when that water is available.

For Colorado, nine interstate compacts, two U.S. Supreme Court decrees, and two international treaties govern water use. These compacts are essentially treaties between states that Congress ratified. Colorado isn’t a direct party to the treaties with Mexico, but international agreements do drive decisions for Colorado’s compacts, Ullmann says. Each compact is specific to a river basin and each is different in how it apportions water. Most are decades old.

“Overall, they’ve held up fairly well,” Ullmann says. “Many of them were drafted with foresight and flexibility that allow them to stand the test of time.”

They also, usefully, created commissions with latitude to interpret and adjust without violating their basic provisions, and even recognize the basic reality that streamflow varies from year to year.

Take the Rio Grande Compact, which relies on gauges along the river’s headwaters to determine the amount of water that has to flow past the New Mexico state line — it’s a percentage of the total annual river flow high in the basin, rather than a set amount.

Still, climate change and ongoing drought are making a tight system tighter.

“The supply and demand imbalance that’s occurring in pretty much all of the West is resulting in challenges in all of our compacts, and that challenge is making sure we comply with them,” Ullmann says.

In the Rio Grande Basin, snowpack has been below average for almost every year of the past 25 years. Even when that basin does see average or above average snowpack, the river flows don’t reflect those numbers: This season, despite 105% of average snowpack in April, mainstem flows were just 75% of normal.

Constraints do appear: on the South Platte, the compact requires a summer flow of 120 cubic feet per second into Nebraska. Sometimes, even with curtailments, there isn’t enough water to raise flows to 120 cfs, but as long as Colorado curtails water rights appropriated before 1897 in the lower portion of the river, the state is considered in compliance with the compact.

Though challenging, Colorado hasn’t yet missed the mark. “We’ve always complied with the compacts in all the basins,” Ullmann says, “which is I guess a point of pride.”

Health & Environment

Colorado’s Public and Environmental Health Improvement Plan for 2024 — the Colorado Department of Public Health and Environment’s (CDPHE) priority issues to tackle — listed two emerging water-focused concerns: PFAS, and harmful algal blooms.

“New evidence suggests some of these contaminants may not be regulated at levels that protect health,” the plan states.

Per- and polyfluoroalkyl substances, known as PFAS, include several thousand man-made chemicals used in various consumer products and industrial applications since the 1940s. Only in the last 10 to 15 years have researchers begun to understand their human health risks. These “forever chemicals” persist in the environment and in human bodies for years after exposure, leading to health concerns with cardiovascular, immune and reproductive systems.

After water providers began detecting PFAS in drinking water, the state conducted widespread sampling to assess where PFAS are found and passed legislation to reduce the chemicals’ presence in consumer products and thus pathways into waterways. Firefighting foam containing PFAS, which can leach into groundwater, has also been banned. Earlier this year, the U.S. Environmental Protection Agency set new drinking water limits for PFAS, which will compel new actions from water utilities to reduce human exposure.

Colorado is also seeing harmful algal blooms that produce toxins and can sicken people or pets in some lakes and reservoirs. These blooms may look like thick pea soup or spilled blue-green paint.

Climate change could cause these algal blooms to occur more often, or at greater intensity, as temperatures and drought conditions increase. Blue-green algae thrives in warm, slow-moving water, according to the U.S. EPA, so as climate change increases water temperatures, the magnitude and duration of harmful algal blooms is expected to rise as well.

These blooms are caused by excessive amounts of nitrogen and phosphorous. At high levels, these nutrients can cause algae to grow faster than ecosystems can handle. Blooms produce elevated toxins and bacterial growth that can make people and animals sick if they contact or drink the water. Algal blooms also reduce oxygen levels in water, killing fish and aquatic life.

CDPHE and wastewater facilities in Colorado are implementing a long-term plan to reduce those nitrogen and phosphorous levels. The first phase of the plan incentivizes nutrient reductions and is expected to be completed by 2027. After 2027, CDPHE may develop numerical water quality limits. Point source pollution for these nutrients can include municipal and industrial wastewater treatment plants, concentrated animal feeding operations, and storm sewer systems, but runoff that carries fertilizer from agricultural fields and residential lawns can also cause nitrogen and phosphorous levels to spike.

Colorado public health officials have sought to reduce the chance of overloading water systems with nutrients by establishing treatment requirements for stormwater and for wastewater dischargers based on available technology and with exceptions for disadvantaged communities. CDPHE also encourages voluntary controls of nonpoint sources, according to Colorado’s Nutrient Management Plan.

In thinking broadly about ecosystem health, stakeholders have developed a few tools to assess risks, prioritize, and take action to address them. Stream management plans use science and assessments to analyze holistic river health and recreation. Integrated water management plans (IWMPs) include more stakeholders and focus on a wider array of needs. By focusing more on water users and values, IWMPs often look at solutions that meet community needs in addition to river needs. Watershed plans work more broadly than IWMPs to focus on watershed health and mitigating risk to water users, often from fires or floods.