Types of Streams & Effects on the Watershed

There are three types of streams in Missouri. The first, known as perennial streams, maintain flow throughout the year except during times of extreme drought. Ephemeral streams see their flow rate vary in direct relation to the amount of rainfall received in the watershed. Finally, intermittent streams have wet and dry seasons, flowing with water during the rainy spring and fall and drying to an underground trickle with occasional shrinking surface pools during the summer (Dasho).

Intermittent streams flow beneath the surface even when they appear dry and are teeming with life, especially invertebrates. The invertebrates provide a vital source of food for larger animals. These streams also provide spawning and nursery sites for many species of important fish. Specialist species, from fish to insects, have adapted to the intermittent flow of the streams and the eggs of some, such as the stonefly, can withstand years of drought (Dasho).

These streams recycle nutrients and energies that sustain the productivity of downstream rivers and lakes, keeping fish populations healthy and strong. They recharge surface and groundwater supplies for human drinking, bathing, irrigation, and industrial uses. They keep the clarity high in other bodies of water and help control floods (Dasho).

Because it’s easy to overlook their importance, intermittent streams are often threatened by human activity. Development nearby can cause erosion, introducing silt and sediments which then choke the streams. Paving with concrete often impacts streams near urban and suburban developments, reducing the ability of streams to prevent flooding. Nearby agriculture can introduce silt and toxic ammonia, killing life and tainting the water. Water extraction can use up the water of these streams in the dry season when they need it most (Dasho).

The harm to intermittent streams can affect fish spawning, food sources, cause extinction, and restrict biodiversity. Because of channelization and habitat loss, some endangered species must be hatched under controlled conditions to maintain populations. Additionally, damage to streams can impact the services they provide to humans such as flood prevention, water filtering, water storage, air cleaning, and recreation (Dasho).