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New Tool Evaluates Riparian Buffers11-09-05 | News

New Tool Evaluates Riparian Buffers

Riparian buffers are wooded or grassy stream banks or wetlands that filter out pollutants such as nitrate from fertilizer and other chemicals, as well as sediment.

According to the scientists at USDA’s Agricultural Research Service, a specially designed field chamber, used together with a computer model, has proven itself as a useful tool to evaluate how effectively riparian buffers filter out pollutants before they can reach streams or other bodies of water.

After success with a prototype chamber in the laboratory, soil scientists installed a field version of the chamber in a tall fescue grass buffer near a forested stream and wetland area. The chamber, which has no top or bottom, encases a 3-by-3-foot block of soil to a depth of four feet. The scientists injected water with dissolved nitrate into one side of the soil chamber. Then, as water flowed horizontally and out the other side, they monitored rates of lateral water flow and loss of nitrate due to its breakdown by soil microbes.

The scientists used the two-dimensional computer model “HYDRUS-2D” to simulate water flow and transport of chemicals within the riparian zone soil. Overall, the model-chamber combination provided good results. The experimental chamber is essential for the accurate use of the growing number of computer models being developed to assess the effectiveness of riparian buffers. Once a model gets this information for a particular location, it can predict nitrate loss rates. A paper on study will appear in the November-December issue of the Soil Science Society of America Journal.