Where there's scum there's...

Not all water quality problems are visible, but here are some common symptoms displayed by unhealthy waterways and riparian zones.

Aggressive algae growth. Nutrients and fertilizers from septic systems and lawn runoff cause algae to grow in rivers in the summer. In recent years, algae have been particularly troublesome in the Clark Fork River, where they make recreation in and on the river less enjoyable, and reduce oxygen levels—harming trout and other aquatic species.

Heavy sediment runoff. Some sediment is natural, but heavy sediment runoff is a sign of increased development—such as cutting new roads—and of unstable, unvegetated banks crumbling into the water. Too much sediment in the water smothers habitat for aquatic insects and hurts spawning habitat for native fish, particularly in small tributaries.

Slimy rocks and discolored foam. Slime on the bottom of Western trout streams is unnatural. So is scummy foam in eddies and backwaters. These problems are often caused by storm runoff carrying sediment, fertilizers, nutrients and other pollutants from streets, lawns, septic systems and agriculture.

Lack of wildlife diversity. If you live along a stretch of river that has been heavily developed, you won't experience the diversity of wildlife found along a healthy river corridor. Riparian areas should be home to a mix of songbirds, waterfowl, deer and small mammals.