Location: Southeast Watershed Research2013 Annual Report
1a. Objectives (from AD-416):
1. Quantify and assess the effects of runoff, erosion, and sediment properties on contaminant transport in agricultural watersheds of the southeastern U.S. 2. Quantify and assess the effects of agricultural conservation practices at multiple spatial and temporal scales in agricultural watersheds of the southeastern U.S. 3. Quantify and assess the effects of interactions among agroecosystems and landscape components on water supply, water quality, and other ecosystem services in agricultural watersheds of the southeastern U.S.
1b. Approach (from AD-416):
This project will provide new knowledge on the effects of soil and water management on water quality, hydrology, and ecosystems services of agricultural watersheds in the Gulf-Atlantic Coastal Plain. Existing and new gauged watersheds form the core research site. The watersheds are characterized by intensive agriculture in upland areas and riparian forests along stream channels. Riparian areas provide baseflow from an alluvial aquifer and storage for storm runoff from adjacent upland areas. Although much of the research is done at smaller scales (plot, field, hillslope), the gauged watersheds allow both extrapolation and testing of technology at larger scales where all of the hydrologic processes important to an integrated landscape or watershed response are present. Cropping practices and patterns in the region are expected to change as bioenergy crops are introduced into crop rotations and on marginal lands. There are concerns about the potential water quantity and quality effects due to increased water demand, expanded acreages, increased inputs, and increased variability in weather and climate. New knowledge is needed on the effects of intensified production on water and soil at multiple spatial scales. Ecosystem services derived from agricultural landscapes, and the potential for conservation practices to enhance these services, also need quantification. The research will quantify: a) processes controlling erosion and chemical transport; b) effects on these processes of new and existing conservation practices at multiple scales; and c) effects of watershed management on water resources and ecosystem services. Research information will be used to better represent these processes in state of the science models. Variable rate rainfall simulation will be used to quantify the effects of extreme rainfall events on sediment and chemical transport and will provide new data to modify and test models to better represent extreme events. Tracer injection techniques will provide new information on flow rates for shallow groundwater and will improve models of field scale transport. The smaller scale studies will provide new information that will enhance understanding at the field and watershed level. Watershed scale hydrology and water quality data before and after bioenergy crop establishment will provide direct measures of their effects when integrated into land management. Field surveys combined with modeling will be used to determine the effects of distribution of conservation practices, water withdrawals, ponds, and irrigation uses on water quantity and quality. Comparisons of urban and agricultural water quality and quantity will serve as a direct measure of an ecosystem service from agriculture. Remote sensing tools will be used to determine how the ecosystem services soil carbon and water holding capacity are related to aboveground biomass production.
3. Progress Report:
Cooperative research with Bio-E-Crops, LLC on watershed scale effects of dedicated bioenergy crop production was established in an ongoing watershed study at the Gibbs Farm Watershed. Fields were planted to Miscanthus X giganteus, a bioenergy crop with promise as a cellulosic biomass source. The Miscanthus plantings account for 37% of the cropland in watershed. Within the Gibbs Farm Watershed, a sub watershed of 19 ha was established with all of the smaller sub-watershed planted with Miscanthus. Sampling of hydrology and water quality from the Gibbs Farm watershed, including the Miscanthus watershed continues. Sampling of watershed sites on Little River Watershed and New River Watershed continues including analysis for pesticides at selected sites. Preparation of the buffer area at the Animal and Dairy Science Watershed has been delayed by wet weather. Bi-weekly sampling of existing ground water wells has been started on the site to get data water quality and water table data prior to conversion of the buffer to bioenergy crops. Archived data from the Animal and Dairy Watershed have been obtained from University of Georgia cooperators and inputs of nutrients from all animal manures used on the watershed have been estimated for 2006-2012. Data on water withdrawals in the Little River Watershed have been obtained from the Georgia Environmental Protection Division/Watershed Protection Branch. A summary report tracking temperature and precipitation changes across the Little River Watershed and comparing these changes to regional climate projections was developed. The analysis indicated that little change in annual precipitation over the Watershed was expected during the 21st century. Some changes in monthly precipitation could be expected, with increased precipitation expected in June through December. The analysis indicated annual air temperature was expected to increase over the 21st century by approximately 0.3 degrees C per decade.
1. Presence of bacterial pathogens in agricultural watersheds not associated with agricultural land use. A byproduct of large-scale broiler chicken production is large quantities of broiler litter -- comprised of bedding material such as wood chips, fecal material, water, and chicken feed. This litter is applied as a soil amendment and may be a source of the bacterial pathogens Salmonella and Campylobacter. ARS researchers at Tifton, GA determined the presence of Salmonella and Campylobacter and other indicator bacteria in multiple streams of the Satilla River Watershed in South Georgia. Both Salmonella and Campylobacter detection frequencies were positively associated with the number of poultry houses in the sub-watersheds, but agricultural land use as a proportion of the watershed was not a significant predictor of either pathogen. Fecal indicator bacterial levels were assessed and evaluated for their ability to predict the presence of the pathogens. Enterococci were most predictive and Escherichia coli was least predictive of the possible presence of the pathogens. Detection of the pathogens throughout the watershed indicated that there was potential for waterborne transmission especially in downstream areas that were more likely to have recreational users.
2. Conservation Effects Assessment Project: Herbicide transport in a coastal watershed depends on timing of application, enhanced degradation rates, and the presence of buffers. Agrichemical transport to coastal waters may have adverse ecological impacts. ARS researchers at Tifton, Georgia used a combination of field studies and simulation modeling to understand atrazine fate and transport in a watershed adjacent to Puerto Rico’s Jobos Bay National Estuarine Research Reserve. Surface runoff due to tropical storms appeared to carry most of the atrazine that moved toward the estuary. Modeling studies showed that the majority of atrazine moved in dissolved form in surface runoff during a tropical storm and that under high rainfall and runoff conditions riparian buffers were less effective at intercepting the herbicide before it reached the estuary. Transport to the estuary was also limited by very rapid atrazine dissipation in the field soil and suggests that atrazine runoff potential is limited unless a tropical storm event occurs immediately following application.
Potter, T.L., Bosch, D.D., Dieppa, A., Whitall, D.R., Strickland, T.C. 2013. Atrazine fate and transport within the coastal zone in southeastern Puerto Rico. Marine Pollution Bulletin. 67:36-44.