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Few moments in life are more mesmerizing than watching clear stream water flow over pebbles, under logs, and through chutes and riffles. We notice the colors, the play of light and shadow, and minnows swimming freely.
In Pennsylvania, healthy streams exist where the input of nutrients is well-matched to the needs of the diverse populations of plants, animals, and microlife. This balance is disturbed by excess fertilizer carried in runoff from our lawns, gardens, and pavement. Other sources of excess nutrients include agricultural and septic systems, soil erosion, and pet waste. Most fertilizers are synthetic and contribute to this problem by quickly releasing their nutrients; extended-release formulations do exist, however. In 2008, a regional laboratory of the Environmental Protection Agency (EPA) found that 40-60% of lawn fertilizer is carried to surface water and groundwater2.
In particular, the growth of algae is enhanced by the nitrogen and phosphorus of fertilizers. According to Dr. Marc Peipoch of the Stroud Water Research Center in Avondale, limited amounts of algae like Cladophora can be helpful in providing aquatic food and shelter. However, “too much [algae] becomes a problem”3. If the supply of nutrients exceeds the stream’s needs, filamentous algae may proliferate, taking up space, blocking light, and degrading the habitat in other ways. Algae can also cause water to develop a toxic alkalinity. As algae die and feed bacteria in the water, it may lower dissolved oxygen to levels insufficient for fish and other life.
Streams are also part of watersheds, so fertilizer runoff into Goose Creek, for example, affects Chester Creek, the Delaware Bay and, gradually, the Atlantic Ocean. This affects our quality of life in several areas including drinking water treatment, fishing, swimming, and boating.
We can prioritize clean and clear water through the careful management of fertilizers. But how can you control the amount of excess nutrients in runoff from your property?
By John Davis, PhD, PE, Associate Professor, Department of Civil Engineering, Widener University for the Chester-Ridley-Crum Watersheds Association, and Eunice Alexander, Township Parks and Recreation Board