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Georgia Water Resources Institute

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https://hdl.handle.net/1853/70796

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School of Civil and Environmental Engineering

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Variation in Hydrologic and Sediment Transport Behavior among the Nine Intensively Monitored Watersheds in the Upper Little Tennessee River Basin

(Georgia Institute of Technology, 2013-04) Bahn, Robert A. ; Jackson, C. Rhett

From late summer 2010 through early fall 2011, hydrology and water chemistry were monitored in nine watersheds varying in spatial distributions of human land use. Monitoring included continuous recording of water level and specific conductivity, regular baseflow sampling, and stormflow sampling with an ISCO automated sampler. Rating curves were developed to convert the stage time series into flow time series. The nine watersheds included two fully forested watersheds, three watersheds with small farms and rural residences in the valleys (classic S. Appalachian land use), three watersheds with small farms and rural residences in the valleys but also with homes built on the hillslopes and ridges (mountainside development), and one urbanized watershed draining the City of Franklin, NC. We analyzed these data to test the following hypotheses: that different land use distributions would produce different hysteretic behavior of sediment concentrations during storms, that the slope of the sediment rating curves would increase with increased valley and mountainside development, and that the high and low flow durations would become more extreme with increased valley and mountainside development.
Identifying Groundwater/Stream Interaction in the Lower Flint River Basin Using Multiple Stream Parameters and Remote Sensing Data Sets

(Georgia Institute of Technology, 2011-04) Rugel, Kathleen ; Golladay, Stephen W. ; Jackson, C. Rhett

Many streams in the lower Flint River Basin are hydraulically connected to the underlying Upper Floridan Aquifer which supplies millions of gallons of water per day to irrigated agriculture throughout the Coastal Plain province of Georgia. Extensive pumping of surface and groundwater within the lower Flint River Basin has resulted in significant streamflow declines, threatening aquatic species which are listed as endangered and threatened in this region. Our research focuses on detecting fracture and dissolution paths between Ichawaynochaway Creek and the underlying Upper Floridan Aquifer. We collected and analyzed stream samples for NO3 -, Ca+, δ18O, and δD, as well as specific conductivity, temperature and pH, at 1 km intervals along a 53 km reach of the Ichawaynochaway Creek in southwestern Georgia, USA. We hypothesized that stream reaches within close proximity to fractures and joints would reflect the chemical signature of inputs from the underlying aquifer. We compared stream chemistry with proximity to various surface features visible on remote sensing data sets in order to identify geomorphological characteristics which might be associated with and predictive of stream-aquifer exchange.
Streamwater Dissolved Organic Carbon and Total Dissolved Nitrogen: Effects of Timber Harvest in the Georgia Piedmont

(Georgia Institute of Technology, 2011-04) Markewitz, Daniel ; Jackson, C. Rhett ; Fraser, Noah ; Radcliffe, David E.

A paired watershed experiment of silvicultural best management practices first initiated in 1973 and harvested in 1974/75 was harvested for a second time in 2004. During the current harvest, BMPs were updated to reflect current guidelines. Stream water yield and physical and chemical attributes were monitored for one year pre-harvest and one year post-harvest. Here we report results for dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations and fluxes. In the treatment watershed, no response to harvest in the discharge-concentration relationship was observed. Based on double mass curves, however, the yield of DOC and TDN increased in the treatment watershed as a result of increased stream water fluxes, although the increased mass of DOC or TDN loss was relatively small.
Simple alternative methods for the biological component of watershed assessments

(Georgia Institute of Technology, 2009-04) Sheridan, Raina M. ; Carroll, G. Denise ; Jackson, C. Rhett ; Rasmussen, Todd C. ; Shelton, James L.

Bioassessments have become useful tools for understanding and rating stream health. The most widely used bioassessments analyze macroinvertebrate communities in order to reach conclusions about water quality. Many state agencies have designed protocols for macroinvertebrate bioassessments and non-government organizations also have adopted their own protocols that are simplified but still effectively measuring stream health. We will compare results from two simplified bioassessment protocols to those produced by the Georgia EPD bioassessment protocol. Our objectives are to determine whether or not the simplified methods produce the same quality data and some inference as that of the EPD methods. We also look at seasonal differences in results to determine whether time of sampling influences results. Currently, our data is limited to four sampling sites in Statham, GA that have been sampled over the fall and winter seasons. We intend to add 11 more sites for fall and winter, and also include spring samples for all 15 sites. Assessment scores varied little over the five sites, and with this limited data set there are inconsistencies of ratings between the two simplified methods compared to the EPD methods. We have also not yet produced any evidence of water quality ratings being affected by sampling in different seasons. Previous studies have shown that at least one of the simple methods produces results consistent to more complex methods, and that macroinvertebrate community structure does undergo seasonal changes. Due to the insufficient amount of data collected at this time, we are unable to reach solid conlusions.
Linkages between simple sediment metrics and aquatic communities in streams of the Piedmond Ecoregion of Georgia

(Georgia Institute of Technology, 2009-04) Carroll, G. Denise ; Jackson, C. Rhett

According to United States Environmental Protection Division and Department of Agriculture, sediment is the number one cause of water quality impairment. Sixteen percent of streams in Georgia are listed for sediment or biota problems, and sediment is typically the assumed cause of biotic impairment. Because sediment loads and stream mobility are expensive and difficult to measure, this study examines the feasibility of using easily measured metrics (e.g., turbidity and percent fine sediment) to explain variability in biotic index scores along a landuse gradient. We measured aquatic assemblage metrics (fish and macroinvertebrates), baseflow sediment concentrations, turbidities, percent fines in the stream bed, local channel slope, and baseflow velocity in 42 streams having a wide range of local conditions and watershed characteristics. Preliminary results indicate that turbidity and suspended sediment concentrations (SSC) were related to forested landuse within a 25-ft stream buffer, but were not explained by overall watershed landuse conditions. Turbidity and SSC were highly correlated when stormflow and baseflow samples were analyzed together, however, baseflow turbidity samples were all less than 30 NTU’s, lacking sufficient variability to replace SSC sampling. Independently, both parameters were weakly related to biotic factors, but explained a high amount of variability when coupled with percent urbanization or impervious surface.
Phosphorus and Sediment in Headwater Streams Draining Poultry Operations in the Upper Etowah River Basin, Georgia

(Georgia Institute of Technology, 2007-03) Romeis, Josh ; Jackson, C. Rhett ; Radcliffe, David E. ; Risse, L. Mark ; Bryant, J.

A 1.5-year monitoring program was initiated in January 2005 to support a University of Georgia study aimed at evaluating nutrient trading opportunities for phosphorus (P) in the upper Etowah River basin in Georgia. Twelve first-order streams were instrumented with hydrologic monitoring equipment and automated samplers. Nine streams drain agricultural (AG) watersheds predominated by poultry operations but different in terms of land use history, best management practices, soil test P (STP) concentrations, and other factors. Three streams drain forested (FORS) watersheds. The monitoring program consisted of biweekly grab sampling coupled with stormchasing. From preliminary results, median low-flow and stormflow concentrations of total P (TP) in astreams were 0-1 and 1-3 orders of magnitude greater, respectively, than in FORS streams. The 3 highest median stormflow TP concentrations in AG streams were observed where 3 of the 4 highest STP concentrations were observed. Median low-flow total suspended solids (TSS) concentrations in AG streams were 0-1 order of magnitude greater than in forested streams. Median stormflow concentrations of TSS between the two land use types were within the same order of magnitude. Streamflow, STP, event mean concentrations, and other variables may be important for estimating P loads from agricultural watersheds monitored for the study.
Piedmont Stream Litter Inputs and Fluxes: Correlations with Riparian Conditions and Urbanization.

(Georgia Institute of Technology, 2007-03) Carroll, G. Denise ; Jackson, C. Rhett

Leaf litter inputs, processing, and retention in aquatic ecosystems are controlled by biological, physical, and chemical factors that can be related to both local reach conditions and large scale watershed features. It is well known that leaf litter is an essential driver of river ecosystem structure, but the complexity of input, transport, and utilization processes has obscured the effects of land management on litter availability. In this study, we evaluated how urbanization affects litter stocks by comparing autumn and spring standing crops in urban and forested streams in the Piedmont of Georgia. We also measured vertical leaf litter inputs across a gradient of canopy coverage and compared the shredder fraction of the macroinvertebrate assemblages between urban and forested streams. Our results indicate that in Georgia Piedmont streams shading appears to be influenced by condition of the riparian zone at the reach scale, while leaf litter seems to be controlled by catchment conditions and factors indirectly tied to land use, such as velocity and timing of inputs. Overall, sites with less urbanization have greater litter inputs during December, however higher rates of retention occur in more urbanized areas, where channels receive continuous inputs from lawns and storm drains. Macroinvertebrate taxa and intolerant species were negatively affected by watershed landuse, although shredder abundance was not.
Hydrologic Behavior of Gullies in the South Carolina Piedmont

(Georgia Institute of Technology, 2007-03) Galang, M. A. ; Jackson, C. Rhett ; Morris, Lawrence A. ; Markewitz, Daniel ; Carter, E. A.

The Piedmont region in the United States has been eroded and gullied due to deforestation and cultivation during the 1700 and 1800. Currently, a majority of these gullies are under forest vegetation and appear stable; however, neither the hydrology of these gullies, nor their sediment contribution to surface waters, has been quantified. This study instrumented eight gullies ranging in size from 36-90 m long, 2.4 to 9.5 m wide, and 0.9 to 3.0 m deep with weirs, stage recorders, and stormwater samplers to assess gully response to prescribed burning. Results from pre-burn data show that only four out of the eight gullies exhibit flow during storm events ranging up to 25.7 mm. Higher rainfall amounts, such as those achieved during hurricanes, may be needed to initiate flow in all gullies. This observation has implications for understanding gully re-activation and associated erosion.
Occurrence of Perched Saturation and Interflow Over an Argillic Horizon in a Low Relief Hillslope

(Georgia Institute of Technology, 2007-03) Greco, James ; Jackson, C. Rhett

Many of the soils in the southeastern US are characterized by an argillic, or clay horizon, that largely parallels the soil surface at depths ranging from a few centimeters to 100 centimeters. The degree to which these argillic horizons alter subsurface movement of infiltrated water is not well known. Interflow, or throughflow, is shallow lateral subsurface flow that moves over a horizon that restricts percolation. This research investigates how often and under what conditions a relatively deep (20-150+ cm) argillic horizon on low slope (2-6%) hillsides causes interflow to occur. Research is being conducted at the Savannah River Site, Aiken, South Carolina, on a small zero-order watershed. In the first phase of this research, a high resolution topographic map of the clay layer was developed. This map will be used to instrument designated “low” spots with max rise piezometers in order to determine if there is channelized subsurface flow. In situ conductivities of the clay layer and the surface horizons were measured using an Amoozegar meter, and bulk density samples were taken and measured. Along with soil topographic measurements, data-logging piezometers have been installed to measure the piezometric head above, in, and below the argillic horizon to further investigate interflow as a potential hydraulic routing mechanism. The stream that drains the catchment was instrumented with a 2’ H flume and data-logging pressure transducer to measure stream flow. Climate data including precipitation, barometric pressure and temperature, are being continuously collected in an open area approximately ¼ mile from the study site. Combining the shallow surface and subsurface piezometric heads with stream flow rates, we should be able to determine if and when the clay layer is contributing to interflow.
Effects of Forest Harvest and Planting on Hydrology and Sediment Transport in Headwater Basins Draining the Pelham Escarpment

(Georgia Institute of Technology, 2007-03) Terrell, Scott B. ; Summer, William B. ; Jackson, C. Rhett

Timber harvesting practices are known to disturb soil and increase bare soil, increase overland flow and peakflow rates, all of which have the potential to increase sediment input to a stream and the erosional power of a stream. These potential water quality issues can have detrimental effects on riparian and aquatic species. Streamside management zones (SMZs) help to reduce the impacts of silvicultural practices. This study is designed to evaluate the hydrologic and sediment transport response during pre-harvest and post harvest periods using a paired watershed approach. Two reference watersheds and two treatment (harvested) watersheds of relatively the same size, shape, geology, and vegetation have been monitored since July 2001. The treatment watersheds will be harvested with the exception of the streamside management zones (SMZs). The SMZs in the will be divided up into upper and lower sections. The upper sections will remain intact and lower sections have undergone partial harvesting in accordance with Georgia forestry best management practices (BMPs). Our results show that there were significant increases in total yield of the treatment watersheds from the pre-harvest to the post harvest period. Peak flows increased slightly in the treatment watersheds after harvest.