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Georgia Water Resources Institute

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School of Civil and Environmental Engineering

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Indicators of Long Term Hydrologic Change in the Flint River

(Georgia Institute of Technology, 2013-04) Golladay, Stephen W. ; Hicks, David W.

The occurrence of three substantial climatic and hydrologic droughts since 1998 has raised concerns about water supply and stream flow throughout Georgia. This concern is acute in the Flint River Basin where low flows of unusual duration and magnitude were observed. The Flint River is essentially unregulated, originating just south of Atlanta and joining the Chattahoochee River to form Lake Seminole in southwestern Georgia. In addition to being an important water supply, the Flint River is noted for its biological and habitat diversity. For our analyses we used long term daily flow records from four stations (USGS: 02344478 – Griffin, 02347500 – Carsonville, 0234750 – Montezuma, 02353000 – Newton) to examine potential changes in hydrologic characteristics. We compared the period of 1940-1974 to 1975-2010, with the later period representing extensive development and population growth in the upper basin, and expansion of irrigated agriculture in the lower basin. Trends in rainfall were compared over the same intervals. No long term changes in annual rainfall were observed. Cycles of above and below average rainfall were observed as were periodic multi-year droughts. Annual water yields (annual CFS/watershed area at the station) ranged from 1.0 to 1.6 CFS/mi2 at all stations during most years. A declining tendency was observed at each station during the 1975-2010 interval, but was only significant at the Montezuma Station (p = 0.04). Winter yields showed similar declines only being significantly lower at the Griffin Station (p = 0.05). Summer yields were lower at all sites and significant declines were observed at Griffin, Carsonville, and Newton (p < 0.05). Calculation of 32 hydrologic indicators showed that the frequencies of low June-September median monthly flows, 1-day, 3-day, 7-day, and 30-day low flows were more common in the 1975-2010 interval at all stations. Our results indicate that human water use is causing increased severity and duration of low flows during the spring and summer seasons throughout the Flint River. These tendencies are pronounced during seasonal and extended droughts. Increased demand is the result of population expansion in the upper basin and irrigation expansion in the lower basin. Current rates of water use are likely unsustainable and pose a significant threat to stream health and the unique biological diversity characteristic of the Flint River.
Coleoptera Indicator Species in Wet vs. Dry Climate Regimes in Three Southwestern Georgia Wetland Types

(Georgia Institute of Technology, 2011-04) Smith, Nathalie D. ; Golladay, Stephen W.

Yearly variation in water availability has a profound effect on the presence and abundance of aquatic Coleoptera (beetles), particularly those dependent upon intermittent or seasonally inundated aquatic habitats. Thirty-four depressional wetlands, previously characterized as marshes, savannas or forested swamps, were sampled during above average and below average rainfall periods (1997-1998 and 2006-2007 respectively). Using Indicator Species Analysis, Coleoptera species were associated with wetland type and hydrologic regime linked to rainfall trends. Relying on species indicator values (p<0.05), marshes contained significantly higher numbers of indicator species compared to other wetland types during both wet and dry periods. Several indicator taxa were consistent within wetland type during the same hydrologic period, but these similarities were not consistent when compared across hydrologic regimes. Species diversity was higher during years with below normal rainfall. These findings indicate that marshes provide more suitable habitat and provide refugia that allow for survival and recovery beetle populations during unusually dry and wet periods. Faced with intermittent aquatic habitat and climate variation, Coleoptera taxa vary in life history characteristics and dispersal abilities which allow long term persistence within the larger landscape.
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.
A Comparison of Gulf Coastal Plain Isolated Wetlands: Water Quality and Larval Mosquito Populations in Agricultural and Reference Sites

(Georgia Institute of Technology, 2011-04) Golladay, Stephen W. ; Vedas, Ellen ; Blackmore, Mark ; Smith, Nathalie D.

Geographically isolated wetlands, i.e. those surrounded completely by upland landforms and vegetation, are a common feature on the southeastern Coastal Plain. As a group they lack surface connection to perennial streams, rivers, or lakes and thus are not regulated under federal or state statutes. Lack of regulation has resulted in widespread isolated wetland loss or degradation, often without an appreciation for their contributions to the surrounding landscape. We sampled water quality and larval mosquito abundance in 10 reference and 10 agricultural wetlands in rural southwestern Georgia from spring through fall 2009. Generally, agricultural wetlands had higher pH, suspended solids, NO3-N, and PO4-P concentrations compared to reference sites. During weekly surveys we collected 23 species of larval mosquitoes from reference sites. Of these, 12 species were not observed in agricultural wetlands including Aedes albopictus, Culex peccator, Cx. pilosus, Cx. quinquefasciatus, Cx. salinarius, Cx. tarsalis, Ochlerotatus atlanticus, Oc. canadensis, Oc. infirmatus, Oc. mitchellae Oc. thibaulti, and Oc. triceriatus. We collected 13 species of larvae from agricultural wetlands including 4 unique species (Cx. coronator, Psorophora columbiae, Ps. discolor and Ps. horrida). Species found in both types included Ae. vexans, Anopheles crucians, An. punctipennis, An. quadrimaculatus, Culiseta melanura, Cx. erraticus, Cx. restuans, Cx. territans, Oc. sticticus, Ps. howardii, and Uranotaenia sapphirina. Ae. vexans and Culex spp. were the most abundant larvae collected. Agricultural and reference wetlands support diverse larval mosquito populations including potential arbovirus vectors, however there has been little systematic sampling in rural areas of the Gulf Coastal Plain.
Stream Flow Changes Associated With Water Use and Climatic Variation in the Lower Flint River Basin, Southwest Georgia

(Georgia Institute of Technology, 2007-03) Golladay, Stephen W. ; Hicks, David W. ; Muenz, Tara K.

In the 1970’s agricultural water use expanded rapidly in the lower Flint River Basin resulting from the introduction of center pivot irrigation technology. The rapid expansion has raised concerns about impacts on regional stream flows essential to support aquatic fauna. Using long-term stream gage records from the USGS and climate data, we analyzed trends in stream flow in two major sub-watersheds and regional patterns of rainfall from 1940 through 2004. We observed no change in annual rainfall but seasonality changed with winters being slightly wetter. Minimum flows showed substantial declines since the development of irrigation. We attribute altered stream flows to increased regional water demand however; the demand for water is also exacerbated by long-term variations in climate and rainfall distribution.
Current Conditions of Historical Mussel Habitat in the Flint River Basin, Georgia

(Georgia Institute of Technology, 2007-03) Muenz, Tara K. ; Opsahl, Stephen P. ; Golladay, Stephen W.

Streams of the Flint River Basin (FRB) remain as viable habitat for many freshwater species and harbor some of the most diverse mussel assemblages in the Southeast. However, land use changes, hydrologic alterations, and declines in native fish species have adversely affected mussel diversity and abundance throughout the region. Protection of rare and sensitive mussels requires the development of timely conservation strategies, supported by knowledge of current riparian and instream habitat conditions that impact their survival and recovery. We examined habitat conditions and selected water quality parameters at 81 stream sites that have historically supported populations of freshwater mussel species in the Basin. Higher nutrient, sediment, and bacterial concentrations were observed in the upper portion (Piedmont) of the Basin, which is characterized by higher gradient streams and percentages of urban land use. Sites in the lower section of the Basin (Fall Line Hills and Coastal Plain) maintained better quality riparian habitat including a larger buffer zone width, greater bank stability, and more vegetative cover. Overall, mussel habitat quality appeared good throughout the Basin. Physicochemical parameters and riparian habitat quality were influenced both by regional geologic differences and patterns of human activity.
Using Adopt-A-Stream in the coastal plain: a look at the macroinvertebrate index

(Georgia Institute of Technology, 2005-04) Muenz, Tara K. ; Golladay, Stephen W. ; Vellidis, George

As major threats to Georgia’s waterways continue, volunteer-based monitoring groups such as Georgia Adopt-A-Stream (GA AAS) have become a vital source of information on aquatic ecological condition. Biological monitoring is an important component of the program, with macroinvertebrates serving as the primary tool for assessing water quality. We evaluated the validity and applicability of the GA AAS macroinvertebrate index on three impacted and two reference streams within an agricultural landscape in the Coastal Plain region of southwest Georgia. We compared these findings to a concurrent study that examined the condition of streams impacted by grazing livestock, through water quality, physical and vegetative parameters as well as macroinvertebrate metrics. The GA AAS index for macroinvertebrates proved to be effective in separating sites with different impacts, showing similar results as most invertebrate indices, and appears to be a valid tool to assess the ecological condition of Coastal Plain streams.
Distribution of unionid mussels in tributaries of the Lower Flint River, Southwestern Georgia: an examination of current and historical trends

(Georgia Institute of Technology, 2005-04) Chastain, Charlotte A. ; Golladay, Stephen W. ; Muenz, Tara K.

The historically diverse assemblage of freshwater mussels in the Flint River Basin (FRB) has shown declines in abundance and distribution. The mid-reaches of the major tributaries of the Flint River contained one of the richest assemblages of mussels in the southeastern Coastal Plain. Declines in mussel assemblages were accelerated by the recent drought that occurred during 1999-2001. Following the drought, we surveyed mussel populations at selected sites in the major tributaries of the Flint River to determine if declines in abundance and distribution were continuing. Many populations of common, rare, and endangered species were stable in their distribution but exhibited declines in numbers. One survey site in particular, on Spring Creek, contains a rich assemblage of mussels unique to this basin, and surveys from this site also suggest population declines. Possible explanations for declines include poor water quality, loss or degradation of instream habitat, competition from the exotic Asiatic clam, and inadequate instream flows.
Comparison of bioassessment methods of ecological condition using aquatic macroinvertebrate assemblages in Southwest Georgia headwater streams

(Georgia Institute of Technology, 2005-04) Winn, Rebecca T. ; Crisman, Thomas L. ; Golladay, Stephen W.

Despite their importance, most biomonitoring programs ignore headwater streams, and focus their usually limited resources on larger streams. This study compared aquatic macroinvertebrate assemblages using Georgia Department of Natural Resources’ (DNR) Georgia Bioassessment Protocol (GBP) and Georgia Adopt-A-Stream’s (AAS) assessment protocol for four relatively undisturbed headwater streams. The rating of ecological condition/water quality of study streams by the GBP and AAS index differed slightly with a greater percentage of samples rated excellent or poor by the AAS index when compared to GBP results. The AAS index detected differences between sampling periods and streams that agreed with commonly used metrics such as Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa. Study results do not suggest that one assessment method is better at describing streams than the other, but they do suggest that the coarser taxonomic resolution employed by the AAS index is adequate to conduct assessments.
Wood debris recruitment from differing riparian landforms in a gulf coastal plain stream: the role of floods

(Georgia Institute of Technology, 2005-04) Golladay, Stephen W. ; Battle, Juliann

Wood recruitment dynamics in Coastal Plain streams are complex. Recruitment rates are dependent on stream valley morphology, forest composition, and flow diversity. Infrequent high flows are critical in the maintenance of the instream debris pool. Following extensive flooding in 1994, surveys of downed trees were made across replicated riparian landforms (floodplains, terraces, and sand ridges) in a Gulf Coastal Plain 5th order stream. Annually, the fate of these trees was determined and newly recruited trees were noted. Generally, tree recruitment was greatest in years with substantial floods (1994 and 1998). For each riparian landform type, tree mortality was correlated with the maximum daily flow during the period preceding annual debris surveys.