USGS contributes to assessing sediment removal in streams
The project was undertaken based on research by Robert Walter and Dorothy Merritts of Franklin and Marshall College. In 2011, after more than 2 years of planning and assistance from the Pennsylvania Department of Environmental Protection, the National Science Foundation, the Environmental Protection Agency (EPA), USGS, and others, bulldozers began to remove 22,000 tons of legacy sediment along 4 square kilometers.
The USGS conducted monitoring and found effects of legacy sediment removal and restoration decreased sediment but effects on nutrients varied. Legacy sediment removal and restoration had significant effects on suspended-sediment concentrations and loads. Median suspended-sediment concentrations at the downstream site decreased from 556 mg/L prerestoration to 74 mg/L postrestoration even though streamflow hydrographs during the two periods were similar. Nutrient concentrations varied in surface water samples depending on the form (particulate, dissolved, organic, inorganic). For example, total phosphorus concentrations at the downstream site decreased from a median of 0.19 milligram per liter (mg/L) to 0.04 mg/L, pre- and postrestoration periods, respectively. Concentrations of orthophosphate, the dissolved form of phosphorus, were not significantly different pre- to postrestoration at the downstream site. Similarly, nitrate concentrations, the dominant form of nitrogen in Big Spring Run surface-water samples (92.3 percent of total nitrogen) were not significantly different in the pre- compared to the postrestoration periods.
The USGS results can be found in https://pubs.usgs.gov/sir/2020/5031/sir20205031.pdf.
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Posted August 26, 2020; Updated August 28, 2020