You may not have heard of the hyporheic zone (HZ) or be able to see it, but it’s an integral part of our freshwater ecosystems and has a lot to do with keeping our streams healthy! The HZ is a transitional area where groundwater and surface water meet. It’s made up of sediments, large and small, but is porous enough to allow the exchange of nutrients, dissolved oxygen, and water. The main movements through the HZ are upwelling and downwelling. Upwelling occurs when water from groundwater moves upward, while downwelling is the movement of surface water toward the groundwater. But water doesn’t just flow through the HZ briefly back and forth; water and its associated materials have a specific residence time in the HZ. This allows pollutants and nutrients to be removed, protecting water quality. Many of these processes are performed by bacteria. Besides bacteria, small invertebrates live in the HZ. Aquatic species like mites and small crustaceans like isopods and amphipods hang out here. And when things get rough in the stream during drought, flooding, and temperature extremes, it becomes a refuge for many species.
The hyporheic zone is found beneath the stream channel and can extend laterally below the banks of a stream. It is the interface between the surface water and groundwater.
Karen Jackson, ©2021, Clemson University
What can we do to make sure the HZ continues to do its job and support beneficial bacteria and invertebrates? Just like anything, the HZ has its limits and can only process a certain amount of pollutants before it is at maximum capacity. Please do your part to prevent pollutants like fecal bacteria, excess nutrients, sediment, and pesticides from entering stormwater runoff and making it into our streams. That means picking up after your pet, only applying the recommended amount of fertilizer, and maintaining a wide area of native plants adjacent to the stream to act as a buffer. To learn more about healthy stream buffers, visit Clemson Home & Garden Information Center or HGIC 1879, Protecting Headwater Streams. You can also take our pet pledge here!
A scud or amphipod is a small freshwater crustacean that lives in streams and can be found in the hyporheic zone. When amphipods are only found in the hyporheic zone, they are generally blind and have no pigment.
Jan Hamrsky, www.lifeinfreshwater.net
