Denver lake and stream recreation starts with a water-quality check

A summer afternoon along the South Platte or Cherry Creek looks like an invitation to wade in. The catch is that these are urban waters, and they carry whatever drains into them.

Denver Public Health and Environment samples the city’s streams and most public lakes, then compares the results with State of Colorado criteria for contact with water. Streams get monitored year-round; lakes are typically sampled in summer. Even so, the standing advice is to use caution in urban surface water regardless of recent results or posted advisories, because the sampling is a snapshot and conditions change fast.

The reason for that caution is upstream. City lakes and streams take in runoff from streets, yards, parks, and various discharges, and the pollution that rides along, including E. coli, can make people sick. Wading, boating, fishing from the bank, or letting kids and dogs splash at the edge all put someone in contact with that water.

A few signs are worth reading as a reason to step back: recent rain, fast or high flows, cloudy water, an unusual odor, or a posted sign. None of those guarantees trouble, but together they tip the odds. Denver’s recreation and water-quality pages carry the current picture when you want to check before getting in.