Authors: Brian A. Clayton, Stephen W. Golladay, David W. Hicks

Radium Springs is the only first magnitude (discharge of over 100 cfs or 64 million gallons per day) spring in Georgia. Increases in water use within the spring’s watershed from agriculture, industry, and municipal users can cause reductions in flow and during times of high water use the spring can cease flowing. The Skywater Project was initiated to restore perennial flows at Radium Springs by reducing water use through conservation measures and diversifying water sources within the springshed. In order to measure responses to hydrologic restoration efforts, a monitoring network was established. Two groundwater sites were instituted and one surface water site on Skywater Creek (the outflow of Radium Springs). Continuous water level recorders were installed at each site and periodic discharge measurement were taken on Skywater Creek. Groundwater wells are less than 2 miles from the Flint River and are highly correlated to stage in the river. Flow reversals in the spring can occur where flooding of the Flint River creates greater head pressure during times of reduced flow from Radium Springs. The groundwater flow system is complex and seasonally variable. Future work will expand the groundwater monitoring network within the springshed.

Human activities can have substantial impacts on watersheds, and a dominant, yet understudied, impact on urban watersheds is the inflow and infiltration (I&I) of water into sewage infrastructure. Information about I&I is especially deficient at the watershed scale. Therefore, this study uses a water-budget approach to quantify the magnitude of I&I for 90 watersheds in the Atlanta, Georgia USA metropolitan statistical area during 2013-2020. I&I for each watershed is calculated by subtracting outflows (i.e., stream discharge, water withdrawn by public water systems, and actual evapotranspiration (AET)) from inflows (i.e., precipitation, water-supply pipe leakage, and non-I&I effluent from wastewater treatment plants. Included in the AET estimates was irrigation water from public water systems and water withdrawals for agriculture. Results show that I&I is a major contributor to outflow in urbanized watersheds. The mean annual I&I total for the 15 most urbanized watersheds is 169 mm and that is 30% of stream discharge. The mean I&I total from the watersheds with the five highest totals is 258 mm, which is 49% of stream discharge. These annual I&I totals align well with totals calculated for urban catchments in Europe. Regression analyses show that the density of older housing, which is a proxy for deteriorating sewage infrastructure, is the most impactful predictor of I&I across the Atlanta region. The I&I findings are promising despite the uncertainties in estimating annual totals for all the components, especially AET, of the water budget. The findings can be applied to other urban watersheds in the southeastern United States, particularly those watersheds in the Piedmont physiographic province.

The Flint River Basin in southwestern Georgia has karst geology containing many geographically isolated wetlands (GIWs). The region also supports intensive irrigated agriculture. Although wetlands that are within or adjacent to crop fields can receive significant runoff of sediment and reactive nutrients (N, P, and organic C), their spatial and temporal storage is poorly understood. Here, we investigated the biogeochemical fate of agricultural runoff on GIWs by applying paleolimnological techniques to sediment surface samples and cores. Our objective was to determine nutrient deposition and storage in GIWs located in agriculturally dominated watersheds. 210Pb-dating, showed the study agriculture wetland received a magnitude higher mass sedimentation rate per year than reference wetlands. Despite high sediment loading, it appears the system is effectively storing and processing nutrients. Low N levels in the agricultural wetland (0.2±0.08%) suggest denitrification ridding the system of excess nutrients. The half-hectare study wetland receives high P loads (25,000 g yr-1) indicating wetlands’ critical role in storage of P in sediment. P loading peaked in 1969 (100,000 g yr-1) plausibly representative of a shift in agricultural practices. The technological advancements of groundwater pivot-irrigation agriculture likely led to a substantial influx of sediment transport resulting in elevated nutrient loads. In intensively farmed areas, remaining GIW’s retain elements of wetland function by processing and storing nutrients prior to groundwater recharge. This study is designed to provide recommendations on best practices for managing runoff and maintaining wetland function at a field and landscape scales to ensure integrity of water resources.

A pilot effort to outline a landscape design methodology specific to karst landscapes was developed using the Dougherty Plain in southwestern Georgia, USA as a study region. A combination of a literature review, regional transect, semi-structured interviews with regional specialists, and qualitative analysis contributed to the formation of four design typologies that are characteristic of the karstic and agricultural properties of the Dougherty Plain. Serving as a foundation for designers to conceptualize the complexity of karst landscapes, and the importance of karst as a harbor for biodiversity and groundwater reserves, this design-research project assembles an argument that karst-specific design methods are necessary for landscape architects if they are to contribute to the protection of natural resources and facilitate the implementation of groundwater protection initiatives on these unique landscapes. The typologies that resulted from these methods serve as a foundation for local stakeholders to consider regional connectivity across the Dougherty Plain by providing a framework for landowners to adopt management strategies at the site scale. As the selected typologies are frequent across the landscape, site-scale interventions that are adopted as part of a landscape-scale initiative would contribute to resource protection, species conservation, and regional groundwater resiliency.

Authors: *Sarah Gregory, Hayley Robinson, John P. Wares, Shayla Williams, Ben Scott, Gail Cowie, Peter D. Hazelton

Freshwater Mussels (Order Unionida) have a unique lifecycle in which the larvae (glochidia) require a fish host for metamorphosis into the juvenile stage. Host relationships may be species specific, and identification of hosts is important for conservation planning. Glochidia morphology can differ among mussel species, genera and tribes, and can be associated with host attraction strategies and targeted host fish. In this preliminary study, we compare glochidia and juvenile measurements (shell length, shell height and hinge length) across early-stage mussels collected from host fish in Flint River tributaries. Identification of a subset of these specimens have been verified by genetic barcoding ID. We will use shell measurements of specimens identified through genetic barcoding, and measurements for species reported in the literature to develop a test set of measurements. Mussel species identifications may be assigned to novel specimens collected but not yet identified using genetic methods.

Authors: *Clarence D. Brookins-Jackson, Zachary L. Boyd, Adam C. Freeland, Brittany L. Mann, M. Katherine Perry, *Amber R. Ignatius

To increase awareness about local water resources, our team developed geospatial educational materials for the 150 km² Lake Sidney Lanier reservoir located in North Georgia, USA. The reservoir is vital for hydroelectric power generation, recreation, tourism, and consumptive uses. Using geospatial analysis in Google Earth Engine, we analyzed precipitation trends in the watershed using Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) data. We also quantified expansion and contraction of reservoir surface area using Sentinel 2 Multispectral Instrument (MSI) imagery. As Lake Sidney Lanier is a managed reservoir, surface water extent fluctuations are related to climatic variables, consumptive use, and hydropower generation.

Water temperature varies based on seasonality, water depth, water clarity, and lake stratification. Changing temperature dynamics affect ecosystem health and determine other important water quality parameters such as dissolved oxygen concentrations. Landsat 8/9 Thermal Infrared Sensor (TIRS) data were used to examine temperature trends over multiple years and investigate the timing of lake stratification and mixing. Highly turbid waters are associated with pollutants and lower water quality and can affect ecosystem productivity by minimizing sunlight penetration into the water column. Sentinel 2 MSI data were processed using a turbidity algorithm to analyze temporal trends and spatial correlations with reservoir inflows. Finally, high concentrations of chlorophyll a were used as a proxy to identify harmful algal blooms. The spatial differences in headwaters and near-dam locations were examined and near real-time satellite data were explored for potential development of early-warning systems to protect ecosystem and human health.

Microplastic is an emerging contaminant of global environmental concern. Pervasive in terrestrial and aquatic ecosystems worldwide, the ubiquity of microplastic pollution has sparked concern about the potential effects on human health and ecosystem function. The myriad sources of plastic pollution present a challenge for quantifying the amount of microplastics entering freshwater environments, necessitating further research to develop a comprehensive understanding of microplastic fluxes into these systems. Although scientists have estimated the amount of microplastic entering marine waters through river transport, limited research has considered spatial and temporal variability in microplastic pollution along river networks, especially in agriculturally dominated areas. In this study, we measured the abundance and composition of microplastics in surface waters on the lower Flint River and its tributaries in southwestern Georgia. Our sampling sites generally corresponded with USGS Stream discharge stations and long-term water quality monitoring sites. Land use in the lower Flint is rural with approximately 35% row crop, 34% managed forest and less than 5% urban. Our study was among the first to document the presence of microplastic contamination in a rural watershed, i.e., the lower Flint River Georgia. Preliminary findings indicated that microplastic types and concentrations were variable throughout the watershed, suggesting heterogeneity of instream microplastics and potential correspondence with land use. The significance of microplastic contamination is unknown for the lower Flint but has been shown to affect aquatic food webs and human health in other marine and freshwater environments.

Watershed management being a vast task and infeasible through physical scouting, scientists must explore the advantages of Geospatial Engineering and Technology based remote application. Lake Lanier Watershed is used as the case-study watershed for developing a ‘Comprehensive Watershed Management Decision Support System (CWMDSS). The CWMDSS includes i) comprehensive landuse change analyses between 1974–2019; ii) SWAT hydrologic modeling from 1992–2020; iii) geospatial modeling to determine the stream segment health using several spatial environmental characteristics; iv) another geospatial model to determine spatially environmentally vulnerable locations in the watershed using 12 different environmental parameters; v) a Modified RUSLE model to determine pixel-based soil erosion amount from the watershed on temporal basis (1991-2019) explaining the land-use change impact on Lake siltation and reservoir volume decrease; and vi) non-point source pollution spatial determination modeling aided by Virginia Tech Bacteria Source Load Calculation (BSLC) to determine spatial sources of bacterial contamination to the waterbodies in the watershed. To add to these analyses, we used 2016 Lake Bathymetry data and 1951 Topographic raster to create DEMs and analyzed the silt deposition volume. We also completed Ponor Grabber aided lake-bottom soil-analysis to understand the erosion impact on lake-life reduction. All these model results were combined together to develop a spatial distribution map of the watershed that explains the environmental degradation on scale-basis. Subsequently, we developed comprehensive best management practices plan to improve the degraded HRUs for enhancing watershed health. These low-cost remote methods for developing CWMDSS can be replicated elsewhere, especially in cash-poor developing countries.

Authors: *Hayley Robinson, *Fareeha Mohammad, *Joseph Stoklosa, Roudnes Loissaint, Daisha Yancey, Matthew Rowe, Benjamin Scott, Shayla Williams, Gail Cowie, John P. Wares, Peter D. Hazelton

The Flint River (GA) harbors approximately 20% of Georgia’s freshwater mussel biodiversity (Order Unionida) with 28 species, several of which are state or federally listed. Leading causes of mussel decline in the watershed include hydrologic alterations, habitat loss through and sedimentation and pollution, and a decline in host fish abundance and diversity. Understanding the unique life-history of Unionids is critical to the development of conservation actions. Larval mussels (glochidia) are obligate parasites on fish and each mussel species can either specialize on certain fish taxa (specialists) or use a broad range of species (generalists). Identification of fish hosts are lacking for nearly 40% of freshwater mussel species in the Flint River basin. In this study we evaluate mussel-host relationships through genetic barcoding of juvenile and glochidia mussels collected from wild caught fish from tributary and mainstem sites in the Flint River. Larval and juvenile mussels were allowed to excise from host fish in the laboratory over a 3-week period post collection. We used PCR amplification of the COX1 mitochondrial loci for individual mussels (~ 250 μm length) and compared loci sequences to those of mussels in the NCBI (i.e., GenBank) database. Preliminary results from June 2021 trials have been sequenced with 70% (n= 89 total samples) containing positive mussel DNA. From this data, 10 mussel species were found to come from 8 different fish species from multiple families (Centrarchidae, Leuciscidae, Esocidae, Percidae). These interactions highlight novel relationships between host fish and mussels. Future research directions will include additional sites to evaluate host infection rates in relation to mussel abundance and comparison of mitochondrial loci performance in species identification.

Authors: *Chelsea R. Smith, Sally A. Entrekin, Stephen W. Golladay, Phillip M. Stepanian, Jennifer L. Tank, Dominic T. Chaloner

Insect emergence is an important transfer of energy from aquatic to terrestrial environments, yet few comparisons have been made at larger scales quantifying estimates of aquatic biomass to emergence biomass. Burrowing mayflies (Hexagenia limbata) are one of the most common North American aquatic insects with predictable mass emergence swarms that can result in pulsed export. Mayfly biomass and growth can be affected by differences in water temperature, food quality and hydrologic disturbance. Lake Seminole provides a unique location to compare aquatic insect biomass, production and emergence because the Chattahoochee River arm is dominated by industrial and urban land use and is heavily dammed resulting in more stable flows, while the Flint River arm is dominated by agriculture and is largely free flowing. These differences in environmental context could alter both temperature and nutrient availability for immature mayflies. We sampled benthic mayflies every 4-6 weeks from February 2021 to January 2022 at 16 sites on the Chattahoochee arm and 14 sites on the Flint arm of the lake to compare differences in cohort growth and the timing of emergence. We then used weather surveillance radar to document the timing and magnitude of adult mayfly emergence to compare with benthic biomass and production. For aquatic samples, we observed multiple cohorts across the lake including distinct differences in development between the two arms. Using radar data, we documented multiple emergence events which coincided with aquatic estimates. However, prevailing winds often clustered emergence biomass making it challenging to distinguish which population was emerging. Given analyses completed thus far, we can document links between measured aquatic growth and radar emergence, with potential to compare changes in past mayfly biomass using historic radar.

Urbanization and climate change are decreasing the overall water quality of streams, and urbanization is expected to increase with projected global population growth. Riparian vegetation can effectively mitigate negative effects of agriculture and forestry, but its effects on the impacts of urbanization are not as well-studied. In particular, little is known about the effects of spatial arrangements of vegetated riparian corridors in urban stream networks. Here we examine whether parklands with healthy riparian zones located at the bottom of urban watersheds can improve aspects of water quality coming from upstream urban. We analyzed summer stream temperatures and nitrogen concentrations in five urban Atlanta streams flowing through Kennesaw Mountain National Battlefield Park (KEMO) and Chattahoochee River National Recreation Area (CHAT). We found consistent negative longitudinal trends in both temperature and total nitrogen across our studied stream reaches, but no correlations with total watershed area, developed area, or canopy cover.

Authors: *Benjamin Webster, Matthew N. Waters, Stephen W. Golladay

Reservoirs are capable of drastically altering watersheds by regulating the flows of streams, depositing suspended sediments and nutrients within reservoirs and preventing downstream transport. Before the Clean Water Act (CWA) some of these nutrients, such as phosphorus, were excessively loaded into streams and rivers from phosphate detergents and minimal regulation on wastewater treatment facilities (WWTF). After the CWA, phosphate detergents were eliminated and phosphorus loading from WWTF was greatly reduced. This is the story of the Chattahoochee and Flint Rivers which experienced the 1960s exponential population rise in the upstream Metro Atlanta area. Here we show the primary findings of how phosphorus and nitrogen are sequestered along the reservoir sequence on the Chattahoochee and Flint Rivers using the natural experiment of the CWA. Phosphorus deposition most closely linked to geographic placement in relation to the primary nutrient source, with the caveat of reservoir retention time exceeding a minimum threshold. Meanwhile, nitrogen deposition was most strongly linked to reservoir retention time, allowing for a greater amount of algae and other organic materials to be deposited. Reservoir retention time can be interpreted as the flow rate through a reservoir, calculated using dam outflow and water storage. Despite how important reservoir retention time is, we normally only consider this as a singular static value instead of a dynamic value that can increase and decrease. Looking forward, we are investigating further into the potential variation and trends of reservoir retention time based on drought conditions and management choices.

Authors: *Benjamin Webster, Auburn University and *Gail Cowie, Georgia Water Planning and Policy Center at Albany State University