What’s Broken in the Creek? Common Water Quality Problems in Urban Streams

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If a seemingly-healthy creek isn’t thriving, what could be wrong? Photo: Krappweiss / CC by 2.0

The creek looks healthy: it wanders through the forest or beside the street, burbling in a way that only small creeks can. But is it truly a happy creek? If populations of indicator species like mayflies and caddisflies are low, this means that there’s something wrong. But what could be the problem? There are a number of different reasons why streams might not exhibit good populations of indicator invertebrates.

Toxins in the Water Cause Problems for Stream Animals

Water pollution is a rather vague term. What could be polluting the water? Many different sorts of chemicals can damage sensitive aquatic life. In urban areas without treatment of storm water, storm drain outlets bring water from roads down into creeks. This storm water may contain fertilizers and pesticides from lawns and oil from roads.

Point source pollution can also be a problem, even in an urban area. If a pool leaks water into a nearby creek, this spills chlorine into the creek. If a local business dumps waste near the creek, this can cause problems as well. Some invertebrate populations such as mayflies and caddisflies are particularly sensitive to pollution.

The pH is Too Far From Neutral

Aquatic life likes to live at a neutral pH, eschewing the extremes. pH runs on a scale from 0 to 14, and neutral is 7, right in the middle. While some creatures can handle life on the edges of the pH scale, most water animals prefer a neutral pH, in which the water is not too acidic or basic. If the water is too acidic or too basic, this changes the environment for the animals. pH isn’t visible, so a pH kit can help you determine how acidic or basic the water is. Over time, you’ll get to know what’s normal for your water.

Warm Stream? It’s Too Hot to Handle

Heat from industrial activities upstream or warm water flowing off asphalt into parking lots can be a problem for water creatures. They can’t turn on the air conditioning. If there’s warm water or a lack of shady spots in the water, this can impact their ability to survive. Warm water holds less oxygen, and animals need oxygen to survive. In a creek with low oxygen levels, animals struggle to glean enough oxygen from the water to survive. Just like pH, you can measure stream oxygen levels to see if that’s the culprit, and measure water temperature with a durable, mercury-free thermometer to see what’s normal for your water body.

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