Healthy riparian zones benefit the community too
by Tiffany Malzahn
In our previous issue of the Brazos Basin, we discussed how riparian vegetation reduces erosion and helps reduce flooding, but did you also know that a healthy riparian zone helps maintain higher water quality?
The root structure and energy dissipation that allow riparian vegetation to control erosion and reduce the impact of flooding, also helps reduce the amount of sediment input into streams, rivers and lakes. By slowing down the flow of water, riparian vegetation allows sediment carried by storm runoff water to settle on land before reaching the stream. By reducing the sediment input into streams, healthy riparian zones help to maintain and improve the river water clarity.
Specifically, the “riparian zone” is the area between the water and higher ground with plant growth. In the riparian zone, water, soil and vegetation interact and the plants that grow in this zone are distinctly different from neighboring plants that grow naturally on higher ground.
OK, so healthy vegetation on the banks of the river make the water clearer. What else?
Well, healthy riparian zones also produce shade. And that’s not just great because it gets hot in Texas.
Shade helps regulate the water’s temperature. Cooler water actually slows the effect of evaporation, which is good since evaporation often consumes twice as much water as the total used by cities, industry, agriculture and mining concerns from the Brazos River Authority system of water supply reservoirs.
The shade also helps to control instream aquatic vegetation, preventing aquatic plants or algae from taking over the stream and making it impassable for both aquatic organisms and recreation, or changing the clarity in the water.
Another benefit from cooler water: increased dissolved oxygen.
Dissolved oxygen levels, – or the amount of oxygen in surface water available for aquatic life, and water temperature are inversely related. The higher the water temperature, the less dissolved oxygen the water can hold. By providing shade and controlling water temperature, healthy riparian zones increase the amount of dissolved oxygen available for fish and other aquatic organisms. Dissolved oxygen is necessary for aquatic species like fish and insects that rely on water for their intake of oxygen, absorbing it through their gills or bodies.
Riparian zones also reduce nutrient inputs by filtering them from upland flow. As nutrients are collected from the landscape during rainfall events and flow toward a stream or lake, it is the riparian vegetation that absorb and utilize the nutrients for their own growth thus preventing them from reaching the stream. Also, like with sediment, the energy dissipating effects of riparian vegetation slows the flow of water allowing for nutrients to be leached into the soil to further support riparian vegetation.
In this way, riparian zones help to moderate nutrient input into streams and lakes thus preventing an overgrowth of algae or aquatic plants in the stream or lake.
All living things are made of carbon and our ecosystem is dependent on balanced cycling of carbon between the atmosphere, water, soil, and organisms.
Healthy riparian zones reduce carbon loads in streams and rivers. Soil and vegetation bind up carbon and prevent it from reaching the stream where an unbalance in carbon loading can lead to it becoming more acidic, especially in coastal streams, estuaries, and the ocean. Acidification of waters can negatively affect aquatic and marine life because all organisms must expend energy to maintain their internal pH and this becomes more difficult the more acidic the water becomes. Also, as water pH lowers from acidification, calcium carbonate, a fundamental building block for a variety of organisms from freshwater mussels to coral reefs, can dissolve in waters with a low pH.
Water is essential for life and ensuring the water quality of the Brazos River basin remains high is vital for survival and success of our communities.
Protecting and caring for its lifeline by protecting its riparian banks will not only safeguard the water quality of the river but will protect human health and the wellbeing of our communities. And educating one another is just one small step to help in that effort.
If you’re a landowner that would like to begin rehabilitating riparian zones on your property, there is help available. You can call on the expertise of Texas A&M AgriLife Extension Service, Texas A&M Forest Service, the U.S. Department of Agriculture – Natural Resources Conservation Service, and Texas Parks and Wildlife Department personnel to help you develop a restoration plan for your property.
Tiffany Malzahn is the Brazos River Authority’s Environmental and Compliance Manager