Feasibility Report and Environmental Impact Statement
Study Purpose
Request for Reallocation: The Colorado Water Conservation Board (CWCB), a division of the State of Colorado's Department of Natural Resources, requested that the Army Corps of Engineers consider reallocating space within Chatfield Reservoir for water supply purposes, on behalf of a group of 15 water users in the Denver metropolitan area.
These water users have looked to Chatfield Reservoir as a potential solution to store renewable surface water from Plum Creek and the South Platte River for storage and use during low-flow periods, which is critical to providing reliable water supplies in Colorado's semiarid climate and can help reduce dependence on non-renewable groundwater.
Regional Water Demand:
Population growth within the Denver, Colorado metropolitan area continues to create a demand on water suppliers. Colorado's population is projected to increase by 65% between 2000 and 2030. The Statewide Water Supply Initiative, commissioned by the State Legislature, estimates that by 2030, water demand along the Front Range will exceed supply by 22%, leaving 90,700 acre-feet (AF) of unmet needs. There is also a strong need for additional water supplies for the agricultural community in the South Platte Basin as thousands of acres of previously irrigated land has not been farmed in recent years due to widespread irrigation well curtailments.
Rights to Renewable Water: Some of the water users requesting the reallocation rely on non-tributary groundwater from the Denver Basin aquifer, which cannot be replenished with run-off water from rain or snow-melt. This non-renewable resource will be depleted over time and become much more expensive to draw upon in the future, because an increasing number of wells will be needed to provide the same amount of flow.
To decrease their dependence on nonrenewable aquifers, many water users have secured rights to surface water in the South Platte River and Plum Creek.These sources are considered renewable, because they can be replenished with seasonal run-off from rain or snow-melt.However, because many of the water users' surface water rights are considered junior, they can only call on this supply when the rivers are high enough to accommodate senior rights first.
Many regional users are looking for a storage solution to capture water when available under their water rights and store that water until needed.Additional storage in a joint flood control-conservation pool at Chatfield Reservoir could provide a solution by allowing storage of renewable water, and partially alleviating the use of nonrenewable groundwater. If approved, a reallocation would help regional water users meet demand for municipal and industrial needs in response to population growth in the region, provide additional water supplies for agricultural and recreational uses, and enhance fisheries and wildlife habitat.
Environmental Regulations: In determining whether to reallocate storage within the reservoir, the Corps must produce a feasibility report (FR) and environmental impact statement (EIS) in accordance with the National Environmental Policy Act, and comply with requirements of the Endangered Species Act (ESA), the National Historic Preservation Act (NHPA), and the Clean Water Act (CWA), among others.