Thursday, August 3, 2017

Riparian Buffer Impact on Stream Health in the Wilson Annis Watershed, Dunn County, WI

As part of the geography team this summer with the LAKES REU program we wanted to find out what measures of stream health riparian buffers impacted most. A riparian buffer is a zone or strip of dense vegetation along a body of water, such as a stream or lake. This zone aids in preventing erosion and pollutants, via stream runoff, from entering the water. The area we chose to examine was the Wilson Annis Watershed in Dunn County, WI. We chose this watershed because it was accessible and because of the implementation of the Wilson Annis Watershed Partnership, a program dedicated to help the watershed. Within the Watershed we chose fourteen sites along Wilson and North Wilson Creek to analyze, where we had to ask landowners for their permission to enter the stream through their property where we were, several times, warned about a bull potentially coming over to the stream.

At our sites, we decided to conduct physical and chemical tests to determine current conditions of the streams. The test we took included temperature, electro conductivity, NTU (turbidity), and dissolved oxygen in order to gather basic chemical samples. Stream velocity and width and depth measurements of the stream were also taken, to determine average stream discharge, macro invertebrate identification three times along each site, and a fish habitat assessment, which measures factors such as bank erosion, pool area, fish cover, and fine sediment presence. To conduct  macro invertebrate testing we had to scoop under banks or scuff on riffles to get all the critters in the net, the most time consuming of the tests, where we identified these critters and later determine the quality of the water based on presence or absence of certain ones.
After weeks of trudging through creeks and multiple mosquito bites, we conducted a correlation test for all of the data gathered to determine the correlation between buffer conditions and the variables we measured. It was found that there was a high positive correlation between buffer conditions and habitat score, on average, the higher the habitat score the higher the buffer conditions were. It was also found that the most downstream sites of both streams had lower habitat scores, due to high sediment, despite having good buffer conditions. When comparing the two streams, they were found to be similar in their discharge, physical, and habitat characteristics. However, monthly monitoring of total phosphorus during 2016-17 found that North Wilson Creek has higher average total phosphorus. This is consistent with our findings that sites along North Wilson Creek both had more fine sediment in the stream bed and higher turbidity.

Riparian buffers, overall, correlate with a better stream habitat. However, with the downstream sites on Wilson and North Wilson Creek demonstrating low habitat conditions, despite having healthy riparian buffer zones, are experiencing influxes of excess fine sediment. North Wilson Creek shows higher turbidity and phosphorus levels, despite excellent riparian buffers at most sites we tested. Other factors influencing runoff and phosphorus levels into the two tributaries could include overall land cover, topography, or slope, soil types, and the use of particular best management practices by farmers and land owners. Conclusively, stream areas with good buffer conditions have healthier habitats, demonstrating that they are very beneficial, and phosphorus differences between the two streams demonstrates that further research can be conducted to determine the cause of the differentiating factor.

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