The following tasks will be performed to meet the project objectives.
Task 1: Develop list of stream sites for potential evaluation
Potential stream study sites will be based on those that have both a USGS continuous streamflow gage and also are sampled through the NCDENR DWQ ambient water-quality program or USGS project activities. The focus will be on active USGS and NC DWQ stream sites that have sufficient data during the past 5 to 10 years for use in determining streamflow characteristics, percent base flows, and nutrient loadings. A list of potential sites to be included in the study is presented in table 1.
Task 2: Compile and process streamflow data
For each study site selected in Task 1, stream-flow data for the 5-10 year study period will be compiled from the USGS National Water Information System (NWIS) database and processed to determine annual streamflow characteristics for use in statistical correlations with nutrient loadings. Hydrograph separations will be performed on the data to determine the amount of base flow, or percent contribution of the annual stream flow derived from groundwater discharge.
Task 3: Compile and process water-quality data
DWQ will provide nutrient data for each of the ambient monitoring stations paired with a USGS stream-gage site. Monthly water-quality data for the past 5 to 10 years will be combined with the streamflow data (task 2) to compute total nitrogen, total nitrate, and total phosphorus loads at each stream study site. At selected sites, part of the analysis will be to determine if the total in-stream nutrient loads can be separated into that derived from both baseflow (groundwater discharge) and from overland runoff.
Task 4: Compile watershed characteristics
Geographic Information System (GIS) information will be used to determine the types and extent of land use, based on 2001 data, within the drainage area of each stream study site. The density of riparian buffers bounding the streams in each study area also will be determined using GIS methods. The numbers and types of point sources (such as waste-water treatment plant discharges) and nonpoint sources (such as livestock feeding operations) will be compiled for each watershed and incorporated in the GIS datasets. These watershed variables will be used in statistical correlations with the stream nutrient loads to better understand those factors that most significantly influence nutrient export in NSW of eastern North Carolina.
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