Citation:

BURKE, R. A., J. MOLINERO, D. L. SPIDLE, AND L. M. PRIETO. NUTRIENT CONCENTRATIONS IN FLOWING WATERS OF THE SOUTH FORK BROAD RIVER, GEORGIA WATERSHED. Presented at Mississippi River Basin Nutrients Science Workshop, St. Louis, MO, October 04 - 06, 2005.

Impact/Purpose:

The overall objective of this task is to identify or develop useful indicators of organic waste enrichment in aquatic systems that are easily measured and based on basic underlying ecosystem processes so that they will be widely applicable. These activities will primarily contribute to an APG within Long Term Goal 2 of the Water Quality Research Program Multiyear Plan: the 2008 APG on equipping EPA Regions, States, and Tribes with knowledge, skills and tools to determine the causes of impairments for freshwater and coastal systems required in various regulations and will also contribute to EPA Strategic Plan 2003-2008 Sub-objective 2.2.2: Improve Coastal and Ocean Waters. Activities that address the 2008 Water Quality APG will focus primarily on small streams of the Georgia Piedmont, which receive human and agricultural waste inputs. The activities related to EPA Sub-objective 2.2.2 will focus on the nearshore marine ecosystem of the Pacific Ocean, which receives treated wastes from the approximately 15 million people who live in the coastal zone of southern California and northern Baja California, Mexico, and on the nearshore marine ecosystem of the Gulf of California, which receives little anthropogenic pollution. The indicators that will be evaluated or developed will include concentrations of trace gases (N2O, CH4, and CO2), dissolved oxygen (DO), nutrients, and dissolved organic matter (DOM), other key parameters such as temperature, conductivity or salinity, flow rate, alkalinity, and pH, rates of key processes such as denitrification and DO consumption, and stable isotope ratios of various pools and substrates such as plants, animals, sediments, and DO.

Description:

The South Fork Broad River (SFBR) drains about 635 km2 of the Georgia Piedmont. The SFBR watershed is primarily rural and undeveloped although the human population increased by about 25% between 1990 and 2000. Forestry and agriculture are the main land uses. Agriculture consists mainly of pasture and poultry operations. Northern Georgia is a major area of US poultry production and massive amounts of poultry litter are generated, most of which is disposed of by land application to pastures near the production site. Further, 90 % of the homes are on septic tanks so there is great potential for contamination by organic waste derived nutrients within the watershed. We monitored concentrations of nutrients, dissolved organic matter (DOM) and other parameters in 17 headwater streams, at three sites on the main stem, and in three major tributaries near their confluence with the SFBR on a monthly basis for over a year. Land use in the small watersheds that we studied was derived from the National Land Cover Data database. Concentrations of DOM, total dissolved nitrogen (TDN), and total dissolved phosphorous (TDP) were more variable in the more disturbed small streams than in the main stem or major tributary sites. Median concentrations of DOM, TDN, and TDP were much more variable among the small streams than among the main stem sites. DOM and nutrient concentrations varied little along the course of the main stem which suggests that relatively little DOM and nutrient processing occurs in the main stem. Watershed organic waste loading appears to be an important controller of small stream chemistry and our results suggest that some of the small watersheds are nearing a threshold of waste loading above which small stream chemistry and ecological function may be disturbed. If disturbance of the small watersheds within the SFBR watershed becomes extensive enough, the main stem may become impaired.

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