Denver Water’s reservoirs are beginning to fill to store the majority of water the utility supplies to its 1.5 million customers in Denver and surrounding suburbs. The area Denver Water serves is projected to increase by almost a million people by 2050. 

To help meet the growing demand for water and improve the reliability of its existing system, Denver Water is planning to expand Gross Reservoir in Boulder County. Gross Dam was constructed in the 1950s and was specifically designed and constructed to allow for future expansion. In the 1990s when Denver Water’s plans to build a new reservoir known as Two Forks was stopped by the EPA, environmental groups and opponents advocated for Denver Water to conserve and reuse more water and raise an existing dam instead. Denver Water embraced those suggestions and implemented an award-winning conservation education campaign, built a recycled water treatment plant and is working on the expansion of Gross Dam.    

Expanding Gross Reservoir is needed to protect Denver Water customers from future drought and projected shortfalls in the overall water storage system. The project will also improve water reliability by better balancing where water is stored in the system.   

Currently, 90% of Denver Water’s storage is in its south system, which draws from the South Platte and Blue River basins. Water in the north system, which is drawn from the Colorado River basin via the Moffatt Tunnel and stored in Gross Reservoir, represents only 10% of Denver Water’s storage. If south system water treatment facilities were forced to go offline because of wildfires, water shortages or other natural disasters, the north system would currently not be able to fill the water demand gap.  

And that’s not just a theoretical concern. Major forest fires in 1996 and 2002 wreaked havoc on the southern end of Denver Water’s storage system, clogging reservoirs with debris and making clear that the north end, with its far more limited storage capacity, can’t bear the burden alone in future disasters.  

Enlarging storage capacity on the north end not only offsets the imbalance in storage, but also will help prevent future shortfalls during droughts, a growing concern with climate change. 

Gross Reservoir expansion is just one facet of Denver Water’s comprehensive strategy, which also includes continued water efficiency, recycling water and responsibly sourcing new supply – to meet future customers’ needs. 

Denver Water is awaiting a License Amendment from the Federal Energy Regulatory Commission, as the facility includes hydropower, which requires FERC evaluate various aspects of the expansion. As we continue the Gross Reservoir Expansion Project, Denver Water may reach out to key stakeholders, including landscape professionals, to share why a secure water future is so critical to the industry and the economy. You can follow the project’s progress at grossreservoir.org.