South Platte River Urban Waters Partnership previews data tools, USGS sampling and funding outlook

Samuel Wallace, the South Platte River Urban Waters Partnership ambassador, briefed the Denver City Council's South Platte River Committee on March 25 about the partnership's mission, a newly developed water-quality assessment tool and recent and planned U.S. Geological Survey sampling aimed at pinpointing pollutant sources along the South Platte River.

Why it matters: Wallace said the partnership's interactive tool and the USGS longitudinal work seek to make monitoring data easier to access, spot pollution "hot spots" and guide locally relevant solutions for algal blooms, nutrient pollution and other water-quality concerns that affect recreation and aquatic habitat.

Wallace described the South Platte River Water Quality Assessment Tool as a dynamic visualization platform that pulls nightly updates from the Colorado Data Sharing Network and the EPA National Water Quality Portal. He said the tool offers both a map of monitoring locations and a sub-watershed explorer that aggregates stations for trend analysis; Wallace showed an example plotting total phosphorus at a monitoring site near 88th Avenue.

Wallace explained the USGS's earlier 2020 longitudinal study followed nutrient concentrations downstream and found spikes near wastewater treatment plants. "You follow one droplet of water along the river and see how that water quality changes as it continues down the river," Wallace said, summarizing the longitudinal sampling approach.

He told the committee USGS teams collected samples during a May 2025 high-flow storm event, sampling from just below Chatfield Reservoir to the South Platte near Henderson, Colorado, and that USGS will return in September 2026 for a planned low-flow sampling event to compare conditions across different flow regimes. Wallace said those more recent samples are still being processed and that USGS plans to produce an interactive web map and deliverables illustrating constituent profiles across the watershed.

Councilmembers asked operational and policy questions. Councilmember Kevin Flynn asked what local conditions might mean for summer flows and pollutant concentrations; Wallace said the partnership focuses on water quality and that low flows can concentrate pollutants from stormwater and other inputs, recommending the Denver Department of Public Health & Environment for quantity-focused analysis. "Sometimes we say that the solution to pollution is dilution," Wallace said, noting that lower flow can mean higher concentrations of contaminants.

On orthophosphate monitoring, Wallace said the 2020 baseline study was partly motivated by a then-planned orthophosphate treatment change at Denver Water. He described nutrients'role in algal blooms and aquatic-ecosystem impacts and said the expanded USGS sampling now includes additional parameters such as heavy metals and salinity under both high-flow and low-flow conditions.

Wallace also reviewed partnership activities: workshops on funding and water equity, field tours of treatment facilities and the CSU Spur campus, a partnership directory and a collaborative projects workshop that drew roughly 30 to 35 partners. He noted grant opportunities oriented to urban waters locations, including USGS cooperative matching funds and the National Fish and Wildlife Foundation's 5-Star and Urban Waters program, with a call-for-proposals and deadlines Wallace said would fall around mid-May.

Funding has been a recent challenge, Wallace said. He told the committee the partnership experienced a significant reduction in federal funds in 2025 but that Aurora Water and Denver Water have helped support the ambassador position and partnership activities while partners explore long-term funding options.

Wallace said the partnership's 2026 priorities are to maintain momentum through collaborative workshops, a partnership project directory and two planned field tours in mid-summer and mid-fall. He said the partnership generally does not speak on behalf of the entire membership on policy positions because of the diversity of partners and federal-entity participation, but it can convene partners, provide data and support outreach to inform local planning.

Next steps: Wallace said USGS will complete the September 2026 low-flow sampling and produce deliverables; he also suggested coordinating a future briefing with USGS and DDPHE to present findings. The committee moved on to consent agenda items after thanking Wallace for the presentation.

Sources and attribution: Quotes and attributions in this article come from the committee transcript and map to the South Platte River Committee meeting record. Where the transcript used only a role label (for example, "Councilwoman Torres"), the article uses that role label as the first reference.