While the world has seemingly come to halt, the need to manage Colorado’s precious water resources has not.
Boulder County Parks and Open Space and the St. Vrain and Left Hand Water Conservancy District are moving forward with a major flood mitigation project at Lake 4, West Lake and A-Frame Pond along the St. Vrain River west of Hygiene.
Once completed in the fall of 2020, the project will restore four breaches in the reservoir and lake embankments caused by the 2013 flood and install outlet structures and emergency spillways for each of the lakes. as well as a more efficient pipeline system for returning water to the St. Vrain Creek.
While this work was largely designed to improve the resiliency of the water storage system, the project is intended to help balance several water demands in the area by improving wildlife habitat as well as return flows to the St. Vrain River — making it an interesting case study surrounding the future of water on the Front Range.
“You’ve got a collision of uses and desires in that area,” said Sean Cronin, executive director of the St. Vrain and Left Hand Water Conservancy District. “You have the gravel mining that occurs in the area, you have the unique ecological habitat that occurs in that area, you have the ditches that thread their way through that area, you have a reservoir, and you have lakes that might provide for some recreational opportunities. We have got to find a balance to be able to provide for all those needs, and I think Lake 4 represents a future potential for our basin.”
Dubbed “creek improvement facilities” by the St. Vrain and Left Hand Water Conservancy District, the project will redesign off-channel reservoirs — or reclaimed mines in this case — so it functions more as an environmental system capable of improving the health of the creek and riparian, rather than isolated bodies of water.
“Pre-flood the area was purchased as individual lakes and a reservoir, with no intention to work as a system,” Cronin said. “That wasn’t due to any lack of vision, it was just the nature of how those lakes are mined and then sold as end-use products. So when the flood hit, it was an opportunity to recognize that that area is actually a system in terms of how the riparian area functions, and also how water might be more efficiently utilized for environmental and recreational purposes.”
As part of the project, more than 220,000 cubic yards of flood-deposited sediment will be removed from the bottom of Lake 4 to restore the water storage capacity of the reservoir and be repurposed as fill material to improve the habitat for native fish in the surrounding lakes, which could then be opened as recreational fisheries.
The new habitat could even be used to raise endangered or threatened species, similar to Webster Pond at Pella Crossing.
“Based on the nature of our watershed and the standard hydrograph, we need water available throughout the year and in different quantities, so storage really makes the Front Range go around,” said Audrey Butler, Boulder County’s water resource specialist. “So how can we think about these storage projects in a more dynamic way that not only benefits cities, industry, and agriculture, but also helps creeks in the way we’re able to release water from these different reservoirs? They’ve got a lot of potential to help out some really stressed systems.”
“When we have more tools in the toolbox as water managers, we can start coming to the table and saying what are the needs of the creek, environment, and recreational users,” Cronin added. “The Lake 4 projects present an opportunity to learn about this tool and perhaps replicate in other parts of the basin.”
