How we impact our watersheds

Almost anything we do to alter the natural landscape has the potential to impact the waterbodies within a watershed. For example, when we install pavement, we create an area of land that does not absorb water. The water that used to soak in, or infiltrate, now runs off and into the nearest ditch or storm drain. This runoff water may pick up pollutants on the surface of the ground, and the increased volume of runoff may erode stream banks and scour stream bottoms. Streams carrying these pollutants flow downhill to a receiving water, or the low point in the watershed. In our case, the receiving water is Lake Thunderbird. 

If streams flowing into the lake carry a lot of sediment, the lake will appear cloudy or turbid. The sediment will gradually settle out of the water and onto the bottom of the lake. In the short term, turbid water is more expensive for the water treatment plant to treat and can lead to waterbodies receiving nicknames like “Dirtybird”. In the long term, increased sedimentation decreases the amount of water the lake can hold. 

When water flows over the land surface, it picks up pollutants in its path and carries those pollutants to the nearest waterbody. In urban areas, common pollutants include pet waste, lawn clippings, lawn chemicals, fluids from automobiles, sediment and trash. In rural areas, common pollutants include sediment, waste from livestock, chemical fertilizers, insecticides and pesticides. 

Natural vegetation traps and filters many pollutants such as sediment, nutrients (nitrogen and phosphorus from natural or synthetic fertilizers) and some chemicals. Nutrients fertilize green plants in the lake just the way nutrients fertilize grass in your yard. Excess nutrients can cause excess algae. When we replace natural vegetation with vegetation like short turfgrass, we reduce the ability of the land to protect waterbodies from pollution.