Gross Reservoir Expansion Project

Photo courtesy of Black and Veatch

Project Purpose

Expanding Gross Reservoir will help protect our customers from negative impacts of a future drought and shortfalls in our overall water storage system. This project will increase Gross Reservoir’s capacity to 119,000 total acre feet by adding an additional 77,000 acre feet. 72,000 acre feet will be for Denver Water use and 5,000 acre feet will go to the environmental pool that provides additional water for South Boulder Creek during low flow periods and provides enhanced stream flow to a 17-mile stretch of South Boulder Creek located below the reservoir. The additional water supply will come from winter and spring runoff during high runoff months of May, June and July. Water will not be diverted for this project during low flow months and when water is scarce. 

The Gross Reservoir Expansion Project is one of the major elements of Denver Water’s long-term supply plan. It will prevent future shortfalls during droughts and correct a serious imbalance in our North-South collection system. With this project, we will provide more water to customers while improving the environment surrounding the planned expansion.

This project is crucial to provide reliability to the Front Range, reduce vulnerability in the event of disasters such as floods and fire, and ensure there is flexibility to provide water from multiple sources when needed. The imbalance between the North and South systems is substantial. Without this project, the North System remains vulnerable in terms of water shortage and reliability if the South System is shut down. This expansion will provide an additional 18,000 acre-feet of water supply for Denver Water’s customers. That’s enough to supply about 72,000 households a year.

Most runoff available to Denver Water during the wet winter of 2014 and spring of 2015 flowed out of state because existing Denver Water reservoirs were full and there was no place to capture and store it after spring rain on the Front Range. This project is designed to capture and store water in average and wet years. If the Gross Reservoir Expansion Project had been completed in 2014 the reservoir could have stored 72,000 acre feet of water in the new storage space by the summer of 2015 for use during dry years.

Governor Endorses Gross Reservoir Expansion Project

Virtual Flyover

Project Materials