Raising Our Stream Consciousness

A healthy stream is like a thriving community; it provides a nice variety of living quarters for equally varied needs. Insects live in the shallow areas of streams where sunlight helps turn vegetation gathered from the stream banks into algae, a food source for this lowest level on the food chain. Baby fish, called larval fish, seek out fast flowing areas called riffles where they can attach to rocks and collect food from the flowing waters. Deep pools in the stream provide cruising spots for schools of fish. Macro-invertebrates such as aquatic insects and freshwater mussels in a healthy stream will get their nourishment from streambanks of lush forest vegetation as leaves and limbs fall into the water.

And just like a community, the aquatic system works best when a proper balance is achieved. Streambanks with mixed vegetation and rich soils will absorb rain and release water slowly into the stream, and filter out pollutants in the process. Streams without the benefit of these natural riparian (stream side) zones lose this important buffer and tend to get “flashy,” i.e. significant amounts of water rush into the stream because there is nothing to slow it down. The natural flow of the stream should gradually increase and decrease during rain events.

Excessive floodwater hits the stream banks and carves out big chunks of soil that lead to excess sediment that will settle on the bottom of a stream. Too much sediment can kill fish eggs, clog the gills of small fish and limit a fish’s ability to see their food.
Culverts and dams can be major problems if they make it impossible for fish to pass upstream or downstream. Water that is too shallow for fish to swim through is also a barrier. Barriers keep fish from getting to areas where they can find food and safe places for laying eggs.

The pH of a stream is a measure of how acidic the water is. Most creatures that live in water can only survive when the pH is about neutral, within a range of pH 5 to pH 7. Some cannot live in water that has any acidity. Chemicals and nutrients that enter the stream through runoff change the pH of the water.

Development also changes the temperature of a stream. Keeping a tree to shade a nearby stream is not always part of a new housing development, while runoff from hot concrete brings warmer water into a stream with less oxygen. As the temperature rises in a stream, the number of aquatic species that can reside there drops.

Jeremy Deeds, aquatic ecologist and classification specialist for the Western Pennsylvania Conservancy stresses that the best way to gauge the health of a stream is different than an economic or recreational perspective.

“Some people tend to judge the state of a stream by how many brook trout it produces.” Deeds said. “But fish may temporarily swim through a non-lethal impacted area or away from an abandoned mine discharge of intermittent duration. To really get an understanding of what’s going on in an aquatic system, it’s important to look at the health of the macroinvertebrate community and some of the more sensitive aquatic insect populations like mayflies and stoneflies. If they exist, that’s an indicator of good stream quality.”
Deeds adds that it is not just western Pennsylvania’s rivers and streams that demand attention, but our nine glacial lakes as well. “Their rarity in this region makes them important and worthy of conservation, “ he said. “And as with our streams, we need to limit development and maintain healthy riparian buffers around the lakes.”

For more information on stream quality, contact Jeremy Deeds, Aquatic Ecologist & Classification Specialist jdeeds@paconserve.org.