Water Quality in Larimer and Weld Counties, 2002–2026

The North Front Range Water Quality Planning Association (NFRWQPA) is the 208 Planning Agency for Region 2. As part of that role, the Association tracks the condition of the streams, lakes and reservoirs in Larimer and Weld counties. Every two years, the Colorado Water Quality Control Division reports on the state’s waters to the U.S. EPA in its Integrated Report. That report is required by Sections 305(b) and 303(d) of the Clean Water Act. The three pages below apply that reporting to our region and extend the record back to 2002. Together they ask one question: Is water quality in the North Front Range improving?

Each page answers that question in a different way. Each one has an interactive map you can drill into, from the whole region down to a single assessment unit.

Regional 305(b) Integrated Report: Larimer and Weld Water Quality, 2002–2026

This page is a regional version of the Division’s statewide 2026 Integrated Report story map, limited to waters in Larimer and Weld counties. It explains how Colorado assesses its waters, including what the reporting categories mean and how waters get on and off the 303(d) List of Impaired Waters. It then shows the 2026 results for the region’s streams and lakes: which waters support their classified uses, which are impaired, and which pollutants are the most common causes. The page also follows the same waters from 2018 to 2026, carries the record back to 2002, and closes with NFRWQPA’s findings on what changed in 2026 and why.

Start here for a plain-language introduction to the Integrated Report and a snapshot of current conditions.

305(b) Integrated Report Water Quality Trends, 2002–2026

This interactive dashboard tracks the “paper record,” meaning the state’s official assessment results. It covers every Integrated Report and 305(b) cycle from 2002 to 2026. You can look at the whole Middle South Platte watershed, the 208 region, a single basin or sub-watershed, or an individual assessment unit. You can also pick a time window from 2 to 24 years. For each area, the dashboard shows the share of stream miles and lake acres that fully attain their uses, how 303(d)-listed pollutants changed over the period, and the status of each designated use. Streamflow at USGS gauges and county precipitation records are shown alongside, so you can read the trends in light of wet and dry years.

Use this page to see how the official listings have changed over time and where.

Physical In-Stream Water Quality Trends, 2002–2026

This page skips the official listings and looks directly at what was measured in the water. It uses monitoring results from the Water Quality Portal, which includes data from USGS, CDPHE, Colorado River Watch, Metro Water Recovery and others. Results are scored against the current Regulation 38 standards in five-year windows that line up with the Integrated Report cycles. The same standards and segment boundaries are applied to every window, so a change in the trend reflects a change in the water, not a change in the rules. The page also compares measured conditions with the 303(d) List. That comparison flags possible emerging problems and possible delisting candidates. It also maps the permitted wastewater discharges in the two counties to the segments they discharge into.

Use this page to check whether the monitoring data agree with the official assessments.

About these pages. These pages were prepared by NFRWQPA to support regional water quality planning. They are based on the Water Quality Control Division’s published reports, Colorado regulations, and public monitoring, streamflow and climate data. They are not official state assessments. Assessment methods, standards and segment boundaries have changed many times since 2002, so long-term comparisons should be read with care. Each page includes a full list of data sources and method notes.