by Nancy Stocker and Polly Reetz
Audubon Society of Greater Denver

Chatfield State Park is one of the most visited state parks in Colorado, with 1.5 million visits annually.

Local and out-of-state visitors come to boat, swim, hike, bike, fish, watch and photograph wildlife, train dogs, scuba dive, ride horseback, and launch hot-air balloons. But major disruptions to many of these activities could occur in the next few years.

A consortium of water providers has proposed storing up to 20,600 acre-feet of additional water in Chatfield Reservoir, which would raise the water level of the reservoir 12 vertical feet. The 2,800 page Draft Environmental Impact Statement (DEIS) evaluates storage of the proposed amount of water, cursorily examines other water supply alternatives, and presents storage in Chatfield Reservoir as the preferred plan. The DEIS does not make clear that only in wet years (about 3 years in 10) would the water be available for storage, as the providers’ water rights are very junior.  In dry years, when water is most needed, the consortium would receive minimal, if any, water. The changes to Chatfield State Park, however, would be ongoing and dramatic.

The plan would remove 300 acres of trees around the reservoir and along the South Platte River, Plum Creek and Deer Creek, replacing forests with mud flats.  These trees shelter hikers and bikers from the sun, especially on sweltering summer days. The cottonwood forest along the South Platte River includes huge trees that are over 100 years old. It is rich with wildlife. Few people, apparently including the writers of the DEIS, realize that these cottonwoods proposed for removal along the South Platte River above Kingfisher Bridge provide nesting sites for birds like the Saw-whet owl and common merganser, a cavity- nesting duck. The dense wooded area that would be removed along Plum Creek provides daytime hiding places for white-tailed and mule deer, raccoon and porcupine. In recent years, a small elk herd has wintered there.

Currently the water level at Chatfield Reservoir is kept fairly stable during the summer months, when park visitation is highest. If the proposed storage plan were implemented, the level could vary up to 17 feet during this period. Although the additional water would be there infrequently, fluctuations in water levels may degrade water quality and cause increased erosion. The swim beach facilities would have to be rebuilt above the expected highest water level. About seven years in 10, this would mean a walk of 500 feet or more for swimmers needing the bathroom. One might question the impact of that on water quality! The marina would have to be re- anchored to deal with the fluctuating water levels. Picnic areas would be rebuilt farther from the water. They would lose the natural shade currently provided by large trees.

You might expect boaters and fishermen would be the big winners from the enlargement of the reservoir. Actually, they would not. Most years the water level will not be significantly different from the current level. The 500+ acres under water about three years in 10 would be shallow, making them unsafe for motor boats and water skiers. The shallow areas are likely to be warmer than the reservoir has been historically, which will create more water quality impacts and degrade fish habitat. Increased water fluctuations will negatively impact the reservoir’s walleye spawning program that involves 30-40 million eggs annually, and the smallmouth bass fishery.

The DEIS indicates the amount of water from the reservoir flowing into the South Platte River through Littleton and Denver would be reduced for nine months of the year, and increased for only one month. This could affect river-based recreation in Denver and add significantly to the costs of sewage treatment for Denver and other municipalities because river water dilutes effluent from treatment plants.

People have begun asking, “Is this undependable storage of extra water worth destroying the heart of a beloved state park and its biological and recreation resources, and reducing flows in the South Platte River below the dam when there are other storage options?” 

Find more information, including a link to the DEIS at SaveChatfield.org. The comment period on the proposal to increase water storage at Chatfield Reservoir ends Sept. 6, 2012.