2025 Perkins County Canal Litigation Update

September 24, 2025

On July 16, 2025, the state of Nebraska filed a lawsuit with the US Supreme Court (SCOTUS or Supreme Court of the United States) alleging that Colorado has interfered with Nebraska’s water rights for the Perkins County Canal in the 1923 South Platte River Compact. This newsletter discusses the provisions of the South Platte River Compact, Colorado irrigation in the South Platte basin, recent South Platte basin developments, Nebraska’s lawsuit, and what to look for as the lawsuit unfolds. 

South Platte Compact. In 1916, Nebraska officials sued Colorado because Colorado water officials were not shutting off junior South Platte Colorado surface water appropriators to meet the needs of the downstream senior (older) Nebraska appropriator, the Western Canal. (In both Nebraska and Colorado, junior (newer) diverters are required to stop diverting when downstream senior (older) diverters don’t receive their full diversion amount.) Colorado offered to negotiate an interstate compact to resolve the issues between the two states, and Nebraska agreed. 

In the 1923 compact, the South Platte was divided into two reaches, the upper reach and the lower reach (see webinar slide 2).  The upper reach is roughly 2/3 of the total length of the South Platte in Colorado and includes what is now the Denver metropolitan region. Under the compact, Nebraska has no claim to water in the upper reach. However, Colorado agreed to regulate junior surface water users in the lower reach whenever the downstream senior Nebraska appropriator, the Western Canal, was not receiving the entire 120 cfs (cubic feet per second – unit of streamflow measurement) it was entitled to, during the April 1-October 15 irrigation season. This is what the 1916 Nebraska lawsuit was filed to accomplish, although not necessarily with the lower reach limitation. 

In addition, the compact provided 500 cfs from the lower reach during the non-irrigation season for the Perkins County canal then under construction. The canal would have diverted water from the South Platte to serve irrigated lands in Nebraska, similarly to the Western Canal. Nebraska would also have been entitled to divert “surplus” flows from the lower reach during the irrigation into the Perkins County canal. However, the Perkins County canal was never developed. 35,000 acre-feet of water from the lower reach was reserved to Colorado for future irrigation development (an acre foot is 325,851 gallons, or enough water to cover an acre of land to a depth of one foot). 

South Platte irrigation in Colorado. The South Platte River basin contains approximately 70% of Colorado’s population, principally the Denver metro area, and about 30% of Colorado’s total irrigated acres. About 55% of the South Platte irrigated acres are supplied by surface water, 17% from wells, and 28% from a combination of surface water and supplemental wells. 

Over time, Denver metro water suppliers acquired additional water to meet the needs of a growing population by purchasing South Platte surface water rights and converting the water to municipal use. This “buy and dry” process, as it is referred to in Colorado, was projected in a 2010 report to result in the loss of 340,000 irrigated acres in the South Platte basin by 2050. South Platte agricultural groups requested Denver metro water managers avoid “buy and dry” in order to protect existing South Platte irrigation and instead get more water from the South Platte itself. We will return to this in just a bit. 

Millennial drought. At the same time, climate change threw Colorado a major curveball that further complicated the South Platte water situation. In 2002, South Platte irrigation began to decline as a result of a devastating and currently continuing drought. Historically, around 9,000 irrigation wells in the South Platte had surface water rights. Because these wells were typically junior to almost all surface water users, they needed to provide replacement water to the river so that there was sufficient water to supply the needs of the senior surface water irrigators. For decades, there was enough unused water stored in South Platte basin reservoirs that ground water users could purchase stored water to provide the replacement water to the South Platte. But when the drought began in 2002, the surplus stored water was soon unavailable to the ground water irrigators. In time, around 4,000 irrigation wells (out of 9,000 total irrigation wells) were required to cease pumping altogether, because they could not obtain replacement water to pump “out of priority” (i.e., when a senior surface appropriator needed the water). In addition, around 1,000 South Platte irrigation wells can pump only two days a week. Colorado is still plagued by this “millennial” drought as of this writing. 

Colorado water planning efforts. The drought stimulated water planning efforts in Colorado. In 2010, the Colorado Water Plan was published, which identified “buy and dry” as the principal way the Denver metro would be able to close its anticipated 2050 municipal and industrial water supply gap. Buy and dry would reduce South Platte irrigation significantly, by an estimated 340,000 acres. After 2010, Colorado water planning proceeded with a regional, river basin focus. In a 2015 South Platte basin report, the issue of irrigation decline due to the Denver metro buy and dry was highlighted. In response, basin interests persuaded the Colorado legislature to commission a study to determine how much South Platte streamflow was potentially available for Denver metro water use, and a later study identified how South Platte streamflow could be used to supply Denver metro water needs. 

The first of these two studies was the 2017 South Platte storage study. The study objective was to identify how much South Platte water left the state “in excess of the minimum amount needed to maintain South Platte River compact compliance.” In other words, how much South Platte water was flowing into Nebraska that was not required by the compact to flow into Nebraska. While South Platte stream flows are quite variable, the study concluded that on average, 332,000-acre feet (AF) flowed into Nebraska beyond bare compact compliance (ranging between 54,000 AF and 815,000 AF). This 332,000 AF would theoretically be available to the Denver metro to help close the 2050 metro region water supply gap. 

Denver metro water interests went to work and funded a study of how these “surplus flows” could be used by the Denver metro instead of buy and dry. The South Platte Regional Opportunities Water Group (SPROWG) – a group of Denver metro water managers--sponsored a study of how “available” South Platte flows could be captured and used in the Denver metro. The result was the 2020 SPROWG report. The report presented and analyzed options for capturing South Platte return flows from Denver metro water treatment discharges as well as natural runoff before it got to the lower section of the river, store it, and pump the water upstream to the Denver metro for treatment and reuse. The water would be diverted from the river just above the boundary between the upper reach and the lower reach (see webinar slide 11). In addition, an additional diversion could be located in the lower reach so that flows into Nebraska could be calibrated to be no more than absolutely required. If fully developed, the SPROWG project would significantly reduce South Platte stream flows into Nebraska. 

Nebraska response. In response to these Colorado activities threatening to reduce South Platte River flows into Nebraska, then-Governor Ricketts proposed $500 million to develop the Perkins County Canal project. Now over $600 million has been appropriated for the project. Nebraska commissioned a feasibility study for the canal project, which was completed in 2022. The study concluded that the Perkins County Canal project would have more Nebraska benefits than costs, that it could be completed in 11 years, and that it would help maintain stable Platte River flows in Nebraska for agricultural, municipal, industrial, hydropower, and environmental water users. In late 2022, an engineering firm was selected to develop the Perkins County Canal project. 

In 2024-25, Nebraska officials approached Colorado landowners to voluntarily sell land to Nebraska for the Perkins County Canal project. Initially, Colorado officials were muted in their response, but ultimately, they publicly encouraged landowners not to cooperate with Nebraska. 

Nebraska lawsuit. Nebraska filed a lawsuit against Colorado in the US Supreme Court (SCOTUS) on July 16, 2025, alleging that Colorado had violated provisions of the South Platte River Compact. Specifically, Nebraska alleges that Colorado has not adequately protected the Western Canal’s senior 120 cfs water right against junior Colorado South Platte ground water users. In addition, Nebraska alleges that Colorado’s system for regulating junior wells in the South Platte basin has diminished the 500 cfs offseason flows for the Perkins County Canal, as well as diminishing the surplus in-season flows for the Perkins County Canal. Colorado has until October 15, 2025, to reply to Nebraska’s complaint. 

It is very likely that SCOTUS will accept the case. When that happens, SCOTUS will likely appoint a “special master,” typically a retired federal judge, to hear the case and report findings and recommendations to the Court for its consideration. This is the same general process that was followed in the Kansas v. Nebraska Republican River Basin Compact litigation and is very common in interstate water disputes. If the Court accepts the case, it will likely take years for the case to be resolved. 

Possible legal issues in the case. Nebraska’s legal complaint alleges that Colorado’s system for allowing junior wells to pump out of priority by providing replacement water back to the river (often during the off-season) reduces South Platte flows into Nebraska during both the irrigation season and the non-irrigation season. I think this is a fair statement of what has happened. But Colorado will likely raise some very interesting legal issues of their own, which could lead to Nebraska’s not being able to pursue the Perkins County Canal project. 

The first issue relates to condemnation. In the South Platte compact, Colorado gives Nebraska the authority to condemn land needed to build the Perkins County Canal project. But the power of condemnation is a sovereign authority that the US government has, and that each state in the US has. And legally, it may be unconstitutional for a state to delegate some of its sovereign powers to another entity, such as another state. I don’t know the answer to this question, but it is an issue that Colorado officials have raised in the media. 

Another issue is whether Nebraska has lost the right to develop the Perkins County Canal project through the passage of time. In general, in western states that follow the prior appropriation doctrine (like both Colorado and Nebraska), the diversion of water and application of the water to a beneficial use must be pursued with “due diligence.” If it isn’t, the water right can only qualify at best for a junior water right rather than a more senior water right based on when the effort to divert and use the water first began. In the Perkins County Canal case, this might mean that the canal could not get a e.g., 1923 date (the compact date) or similar very senior date for the canal water right, but rather say a 2022 date, when the engineering company was selected to develop the canal. In the general case where the entity pursuing the water right is not a state, this due diligence requirement would prevent most would-be appropriators from acquiring earlier dates for their water right. But in the Perkins County Canal case, the state of Nebraska is a sovereign state to whom courts often give far more latitude in meeting some of these more technical legal requirements. If that were to be the case for the Perkins County Canal project, Nebraska would be able to develop the canal say from 2022-2033 and get a 1923 date for the canal water right, even though nearly a century had lapsed between the original canal development in the early 20^th century and the ultimate project completion in the early 21^st century. This is one of those issues that courts make on a case-by-case basis, and it is impossible for me to usefully speculate on how the Court might rule in the Perkins County Canal case. 

There is one legal wildcard that must be acknowledged. State and federal law place a very high priority on the protection of threatened or endangered wildlife species. The big bend reach of the central Platte River, roughly from Lexington to Chapman, is protected critical habitat for the endangered whooping crane and other wildlife species. If Nebraska could demonstrate that the Denver metro South Platte water supply projects would reduce flows through the critical habitat in Nebraska, and that the Perkins County Canal project would protect those critical habitat flows, that would, in my opinion, be likely to strengthen Nebraska’s case for the Perkins County Canal project under the South Platte River Compact. 

J. David Aiken, Professor
Water and Agricultural Law Specialist
University of Nebraska - Lincoln
Department of Agricultural Economics
daiken@unl.edu
402-472-1848