By Tom P., October 8, 2021

Earlier this month a few members of various Trout Unlimited chapters in Colorado met for a tour of the proposed Wild Horse Reservoir. The tour and presentation were given by Aurora Water representatives at the proposed location in South Park. The representatives were very passionate and I learned a lot about the water issues and challenges that they face.

In a nutshell, 80% of Colorado’s population lives on the Front Range, and 80% of Colorado’s water is west of the Continental Divide. Cities like Denver, Aurora, and Colorado Springs have purchased water rights all over the state, and engineers have designed a complex water delivery system to move the water east. It is a really impressive system — water stored in reservoirs, piped up over mountain ranges, sent down natural rivers and creeks, then moved again. Apart from the dewatering impacts to the original watersheds, which is not my aim to discuss, we sometimes do get some benefit from some of that water flowing down the Arkansas river.

Water management is a very complicated process – while the demand side is fairly well known, the supply is extremely variable. I tried to explain it as best I could in layman terms, but that involved a lot of oversimplifying. Greg Baker from Aurora Water, one of the presenters on the tour, kindly made some comments clarifying some issues. I took the liberty to quote them verbatim, as to both have the proper explanation and to shed light on how complex this process is. Each quote is attributed and in italics for clarity.

Aurora Water's water supply chart
Map of the Aurora Water’s “plumbing” system

Some of the challenges that I found interesting:

– Aurora owns only 2,700 acre-feet (AF) of storage in Twin Lakes. That is not much, and Aurora moves 50,000 AF (!!) through that reservoir a year. That means that whatever water they get from the Colorado river watershed has to pretty much go right through Twin Lakes into the Arkansas. [Greg Baker: Water gets complicated. From Twin Lakes, our Colorado River water uses a pipeline to our pump station outside of Buena Vista. Here it’s moved into the S. Platte basin. Our Arkansas River rights, mostly from the Rocky Ford area, do impact the Ark since we move them from Pueblo Reservoir to Twin Lakes (via exchange, but that means water is moving down the river to meet the needs fo whoever we exchange with). We are part of the Browns Canyon Flow Program, which helps ensure minimum flows between Twin Lakes and Pueblo Reservoir from July 1 – August 15 to maintain a healthy fishery and help the recreational boating community.]

– They have limited amounts of storage in various reservoirs. If reservoir managers expect increased runoff and have to “make space” for it, they can force Aurora to move their water. If Aurora has limited amount of storage downstream, then sometimes the water has to be “spilled” — dumped into the river, flowing through other catchments, down into Kansas.

– The city of Aurora uses about 50,000 AF annually. Their total available storage, across the entire system, is 155,000 AF. In other words, if their system was filled to capacity, they would have 3 years of usage. This is not a long time, considering climate change, drought in the West, and the decreasing annual snowpack.

– Aurora can use an exchange system to trade water — since water from Pueblo Reservoir is hard to transport to Aurora, they can exchange it for water that’s at higher elevation closer to their “plumbing” system (e.g. to Twin Lakes or Turquoise). Quite a lot of this goes on, allowing water utilities to make use of water they have rights to but that is difficult to access.

– Water movement is pretty tightly regulated. The VFMP on the Arkansas dictates exactly how much water participants can move, and when, as to maximize benefits to the fishery, the rafting industry, agriculture, etc.

Aurora Water's storage and supply chart.
Chart showing Aurora’s water storage capacity vs. supply over time. Note the last 5 years — each peak is successively lower, reflecting the decreasing amount of runoff every year.

Currently, water from the Colorado river watershed moves through Twin Lakes, then down the Arkansas to about Rapid #5 on the Numbers section. [Greg Baker: We do have an alternative diversion at Granite, the Arkansas River Diversion, that we just rebuilt in cooperation with CPW, CWCB and others, where could divert water directly from the Ark, but that is a back-up diversion only. Due to the large amount of water that we and Colorado Springs Utilities move through the pump station, we prefer not to use the river diversion unless absolutely necessary].

The Otero Pump station is able to pump a huge amount of water over the mountains, moving it from our river to the South Park valley. Currently, that water runs through the Spinney channel and dumps directly into Spinney Reservoir. The channel is open to the sky, freezes in the winter, has evaporation issues in the summer. It runs about 200cfs, and moves about 150 AF annually. From Spinney, the water runs through the Dream Stream, Elevenmile Reservoir, and down through a network of other storage reservoirs.

Water from the South Platte drainage, which comes through the South, Middle, and North forks of the South Platte river, currently flows directly into Spinney Reservoir. I’m sure that many of us fished the various sections of those rivers in South Park.

Aurora has about 53,000 AF of storage in Spinney itself. One of the big challenges they face is that in years with a lot of runoff they get too much water in store in Spinney. Remember — water from both the Colorado and Arkansas river watersheds goes into Spinney as well. If the Platte river is coming in full, then Spinney has no space to store the water from the Colorado river. So all that water goes into Spinney and gets immediately spilled through the Dream Stream, going down the system, the water has to go down to Pueblo Reservoir in an unconstrained manner. [Greg Baker: Again, complex. If we see that we’ll have a huge yield in the S. Platte, we may delay pumping from Twin, but that means we have to release anything we can store in Homestake, Turquoise or Twin into the Ark in an unconstrained manner. This may result in too much flow that could impact the fishery in the spring, which impacts spawning. On the other hand, if we have a year like 2020-21, where we had a very late heavy snow ad rain event in the upper S. Platte, we have already filled Spinney with CO and Ark water, and then have figure what to do unanticipated Platte water. This impacts the Dream Stream and the Platte downstream of Eleven Mile (that’s a flood control reservoir, so they have to pass our excess flows right through].

Touring the site

To remedy this issue, Aurora is planning to build a new reservoir called Wild Horse. It would be located in South Park, west of Spinney. It would store exclusively the water that comes from the Colorado and Arkansas river watersheds, through the Otero pipeline. This reservoir would add about 96,000 AF of storage (remember: current total storage is 155,000 AF). The Wild Horse location is on private land, with some existing rock formations that make most of a natural bowl. Three dam sections would have to be constructed, and they would be a lot taller than Spinney’s. Maximum depth would be 197′, and it would have a much smaller surface area than most current reservoirs.

There is a lot less surface evaporation at higher elevations. It stands to reason — air is colder, water stays colder as well. But the numbers are staggering — it is estimated that annual evaporative loss at Wild Horse would be about 3′ a year (meaning the water level would drop 3′ annually). On the Front Range, which is lower in elevation and a lot warmer, that loss can be 45′!

Wild Horse reservoir would allow Aurora to store all the water that comes from the Colorado river and Arkansas watersheds, and send it on through Spinney as needed. It’s a natural place in the system to interrupt the current water flow, and it would allow Aurora to optimize the storage they have in Spinney. If a lot of water is coming down the Platte, they could store that water in Spinney, and hold back the releases from Wild Horse.

They are proposing an underground pipeline from Wild Horse to Spinney, which has a variety of advantages over an open channel system. Being underground, it wouldn’t freeze and it wouldn’t suffer evaporative loss. Rather than have the water always going into Spinney (up to their storage limits) when there is runoff, the water could be moved on as-needed basis throughout the year.

So far, the project seems to have only benefits:
– The land it is being built on is private
– The reservoir is off-stream, so it’s not impacting any waterbody
– No new water rights are involved — nothing is getting de-watered elsewhere
– The design is smart, prioritizing depth and smaller surface area
– It’ll allow Aurora to better leverage the runoff from different watersheds
– It increases their overall storage capacity by about 60%
– They will be in talks with CPW about making it available to recreation.

A few longer term questions come to mind:
– Will the Spinney inflow be of drastically different temperature to affect that fishery?
– Any chance for some invasive species to take hold in the new reservoir and travel downstream to others?

Aurora Water is now going through the process of securing all permits, doing environmental assessments, etc. If the permitting goes through as hoped for, they plan on start construction in about three years.

In this article, I have not touched on Aurora’s conservation work — the Praire Waters plant which recycles used water. How native water can be used only once before having to pass onto the next water right owner, but how transbasin water can be used over and over.

For more information about this project, check Aurora Water’s Wild Horse reservoir fact sheet.

by Keith Krebs, reprinted from The Mountain Mail, May 7, 2020, edition

The South Arkansas, known as The Little River to many locals, is an important tributary of the main stem of the Arkansas River.

Historically, flows in the South Arkansas were larger and more varied than at present. The physical footprint of today’s river reflects natural processes that are largely no longer at work. Today, there is often not enough water for the
original channel, and that limits the river’s ability to sustain a fully functioning ecosystem.

The South Arkansas River Watershed Assessment was completed in May 2014 by Bill Goosman at the request of Collegiate Peaks Chapter of Trout Unlimited and the Land Trust of the Upper Arkansas, now the Central Colorado Conservancy (CCC) and offers comprehensive evidence that today there are two different South Arkansas rivers.

The first is the upper reaches with its physical template created over millennia. The second arises gradually downstream as the impacts of past and present human activity intensify, creating a river less able to function properly. A line between the two rivers is crossed in the vicinity of Chaffee County Road 210.

In the upstream portion the influence of human activity is moderate, allowing more diverse habitat, limited sediment disposition, fewer barriers to fish movement and healthy, functioning plant communities.

Downstream the adverse impacts from human activity accumulate through more intensive and extensive use of water and land that have degraded in-stream and streamside habitat quality and quantity.

The river channel has been straightened with fewer areas of slower, deeper water, areas of sediment disposition are larger and more frequent, the riparian habitat is degraded or eliminated, and the river has been disconnected from natural and historic adjacent wetlands areas.

The South Arkansas River is a tremendous biological resource. From its origins high in the Sawatch Range, the South Arkansas flows along and through public lands, ranchlands, businesses and residential neighborhoods, providing drinking water to the city of Salida as well as valuable habitat to the many wildlife species that use the river corridor.

While rivers and wetlands make up only 2 percent of our land cover in Chaffee County, 80 percent of wildlife species use them at some point in their life cycle. Healthy riparian areas, or the green ribbons of vegetation that line rivers, act as a living filter and help attenuate floods, enhance water quality and recharge groundwater.

Central Colorado Conservancy and Collegiate Peaks Chapter of Trout Unlimited are teaming up with local landowners to study opportunities along the South Arkansas River to improve water quality, riparian habitat and fish habitat while at the same time supporting landowners and their goals.

While this work is focused on maintaining and improving health of the overall watershed, we are currently engaged in an exploration of opportunities for a 1.2-mile reach of the South Arkansas River from CR 107 downstream (east) to the confluence with the main stem of the Arkansas.

We have used grant and donation funding to hire a consortium of locally based expert consultants who are completing a river health assessment, and along with adjacent landowner input, developing a conceptual design for enhancement along this reach of the Little River. We hope to have completed this phase before year’s end. Volunteers from Collegiate Peaks Chapter of Trout Unlimited and staff from the Greater Arkansas River Nature Association are collaborating to implement the Colorado River Watch water quality monitoring program on the South Arkansas. The River Watch program is defined as “Real people doing real science for a real purpose.” True citizen science that we want to continue into the foreseeable future.

After completing 48 hours of training and in possession of several hundred dollars of testing equipment, three volunteers expect to complete our initial on-site sampling sometime this summer. Look for us on the Little River near the pedestrian bridge. We hope to expand to additional sites in the future, hopefully including some sites on the main stem of the Arkansas as we acquire more resources and as additional volunteers are trained. It is a long-term commitment to monitoring the health of our rivers.

For more information about Collegiate Peaks Chapter, including our events and projects, visit our website,

Keith Krebs is chapter president and youth education coordinator for Collegiate Peaks Chapter of Trout Unlimited.

by Keith Krebs and Daniel Omasta

The drought of 2018 was a tough one for Colorado – especially for rural communities that battled catastrophic wildfire or watched irrigated fields go dry and saw tourists leave as the rivers were closed and fires were banned.

While this winter has brought much needed relief to our watersheds, we cannot forget how connected we are to the swings of any given water year.

The Arkansas River Valley is fortunate in its ability to develop collaborative projects that improve our collective resources and defend against the hardships of tough years like 2018. The Voluntary Flow Management Program (VFMP) in place on the Arkansas River, for example, helps stabilize flows for heathier fish populations, provides much needed water for the rafting seasons and continues to meet the demands of irrigators and downstream decrees.

In 2018, the VFMP made a big impact for our local fishing guides and rafting companies by providing flexibility and better timing of a very tight water budget. While much of the rest of the state had closed its rivers and shops shut their doors for the summer tourist season, the Arkansas River was able to remain open.

The flow management program was a major reason that our valley was able to stave off at least some of the economic and environmental sting of last year’s drought. A big reason that the program operated successfully is because water managers, utilities, irrigators, recreational users, conservationists and community leaders were able to find common ground and mutually beneficial solutions.

This spring, the Colorado General Assembly can take the opportunity to learn from our success in the Arkansas Valley and pass HB 19-1218 – the “Loaned Water for In-stream Flows to Improve the Environment” Act. This bill will expand opportunities for in-stream flow leases and the ability of water rights owners and river communities to work together.

An “in-stream flow right” (ISF) is a water right that is held by the Colorado Water Conservation Board and protects flows between specific points on a river, to preserve or enhance the natural environment. These decrees go through a similar process as consumptive rights and must prove that they will not injure a downstream user or senior water right.

Often, these ISFs are junior to most of the other water rights on a stream and therefore are last in line to get the water. In drought years, they may not see that water at all.

In 2004 state legislators passed a bill that allowed for temporary and voluntary leasing of water to ISF rights. With the approval of the local district engineer, senior water owners could lease water to ISF rights and be compensated. It was a win-win for the irrigator and the stream.

Unfortunately, provisions in that original legislation limited the ability of that water right owner to lease some of their water for no more than three years out of a 10-year period without the ability to ever renew their agreement.

The Loaned Water Bill (HB 19-1218) is not a new program but helps open the door to further collaboration among Coloradans in tough drought years. The bill increases the number of years that water can be leased to five out of a 10-year period, as well as extends opportunities for renewal within the existing ISF program.

This improvement in the 2004 legislation will allow irrigators and water managers to have more flexibility to generate revenue and protect our way of life. These important changes will also enable the Colorado Water Conservation Board and local biologists to protect streams during multi-year droughts.

Strong flows and healthy fisheries are significant economic drivers for rural communities and tourism across the state – including the Upper Arkansas River Valley. In 2017, outdoor recreation activities, such as fishing and rafting, combined to generate more than $62 billion in economic impact and supported 511,000 jobs in Colorado (from CPW for 2018).

Fortunately, water users in many areas of Colorado have already demonstrated their ability and willingness to find mutually beneficial programs that protect water rights while providing benefits to small businesses and the environment.

We have proven that these programs can work here in the Arkansas River Basin, and Collegiate Peaks Chapter of Trout Unlimited supports our leaders who continue to support the ability of water users to work together to find local solutions.

For more information about Collegiate Peaks Chapter, our events and projects visit our website,

Keith Krebs is a current board director and chair of the Youth Education Committee of Collegiate Peaks Chapter – Trout Unlimited, and Daniel Omasta is the local grassroots coordinator for Colorado TU.