Organizational Unit:

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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Now showing 1 - 10 of 18

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.
Incorporating the cold-water pool in Lake Lanier conservation storage management

(Georgia Institute of Technology, 2009-04) Zeng, Wei ; Rasmussen, Todd C. ; Couch, Bill ; Zhang, Yi

Lake Lanier typically declines during the summer and fall to meet downstream flow requirements. While low lake levels during the summer and fall of 2007 caused concerns about depleting the conservation pool, another concern is the depletion of the cold-water (hypolimnetic) pool that lies below the surface warmwater (epilimnetic) pool. Typically, the lake is stratified during the summer. Discharges at Buford Dam are mainly from the deeper, cold-water pool, which is normally replenished during the winter and spring. The Buford Fish Hatchery - and the designated trout stream downstream of Buford Dam - depends on these cold-water releases. Increased lake discharges may exhaust this pool of cold water before winter inflows replenish it. This study uses historic data to predict the potential decline of the cold-water pool as a function of reservoir releases. The decline may be used to forecast downstream water quality impacts resulting from alternative Lake Lanier operations.
Internal Loading in Southeastern Piedmont Impoundments

(Georgia Institute of Technology, 2007-03) Ceballos, Elena L. ; Rasmussen, Todd C.

In Piedmont impoundments in Georgia, as well as lakes and impoundments throughout the world, accelerated eutrophication of lakes causes detrimental ecological effects such as algal blooms, lake anoxia and toxic metal release from sediments. It often renders water unsafe for agricultural use, recreation and drinking. To reduce the eutrophication of local Piedmont impoundments, recent regulatory controls for nutrients were established as part of the Clean Lakes program and courtordered total maximum daily loads. These regulatory efforts focus on the reduction and minimization of pointsource watershed nutrient inputs, primarily phosphorus, into lake systems, as phosphorus is the limiting nutrient in Piedmont impoundments. Reductions in phosphorus loading are expected to improve lake water quality. However, in the Piedmont, as well as worldwide, many lakes continue to experience algal blooms and lake anoxia after sources of external loading are discontinued. Internal loading has been identified to be a source of algal available phosphorus, as well as other nutrients. The conditions under which internal loading takes place are region-specific as they vary based on local physical, chemical and biological conditions. The purpose of our research is to quantify changes in algal biomass in response to internal loading from resuspended sediment in Lake Allatoona, Georgia. The results of a mesocosm experiment are used to evaluate potential appropriate remediation strategies to minimize detrimental algal blooms in Southeastern Piedmont impoundments.
Effects of Seasonal Variation on Runoff Curve Number for Selected Watersheds of Georgia - Preliminary Study

(Georgia Institute of Technology, 2007-03) Tedela, Negussie H. ; McCutcheon, Steven C. ; Rasmussen, Todd C.

This study examined seasonal effects on the runoff Curve Number for five forested watersheds in Georgia. The periods between April-October and November-March were defined as the growing and dormant seasons, respectively. Annual maximum peak runoff data were used to select one pair of rainfall and runoff volumes for each water year. The Curve Number method was used to determine Curve Numbers using these observed precipitation and runoff values. Based on the date that rainfall and runoff volume were observed, the Curve Number values were grouped to their respective seasons for statistical analysis. The results from all watersheds showed higher mean Curve Numbers for the dormant season compared to the growing season. However, statistically significant differences between mean Curve Number values for the growing and dormant season were detected for only two of the five watersheds. Depending on the availability of data, selecting two or three representative months for each season would likely result in a better prediction by avoiding transition periods between the two seasons.
Results from Six Years of Community-Based Volunteer Water Quality Monitoring By the Upper Oconee Watershed Network

(Georgia Institute of Technology, 2007-03) Little, Elizabeth ; Eggert, Sue ; Wenner, David B. ; Rasmussen, Todd C. ; Conners, Deanna E. ; Fisher, Dwight S.

The Upper Oconee Watershed Network (UOWN), an Athens, GA-based non-profit volunteer organization, was organized in 2000 with the mission to improve water quality in the Upper Oconee River basin through community-based advocacy, monitoring, and education. Quarterly monitoring of both reference and impaired stream segments form the basis for achieving all three of UOWN’s mission objectives. UOWN has developed a model for engaging the public in quarterly monitoring and in the larger annual River Rendezvous events. Quarterly monitoring not only tracks long-term trends in targeted stream segments, but also has resulted in the discovery and remediation of acute incidences of pollution. Six years of data collection revealed high levels of contamination in urban streams as evidenced by high conductivity and bacterial numbers, and potential limitations when using quarterly water quality monitoring to assess the health of Piedmont streams.
Identifying sewage leaks in urban environments: Examples from Athens, GA

(Georgia Institute of Technology, 2005-04) Carroll, G. Denise ; Rasmussen, Todd C.

Sewer line failures are a major cause of stream impairment in urban areas. While many sewer line failures can be readily identi ed and cor- rected, other failures may be more di cult to rem- edy. This paper examines the general problem of sewer line failures. Speci cally, we discuss 1) the observed causes of sewer line failures, 2) methods for determining which streams are being a ected by sewer line failures, and 3) strategies for pinpointing the exact location of these failures so that they can be repaired. Examples of sewer line failures within Athens, Georgia, are used to illustrate the problems with identifying these failures.
Use of green roofs for ultra-urban stream restoration in the Georgia Piedmont (USA)

(Georgia Institute of Technology, 2005-04) Carter, Timothy L. ; Rasmussen, Todd C.

Stormwater management has tra- ditionally focused on the use of conveyances to quickly move stormwater runo from urban cen- ters into nearby rivers, streams, and lakes. The increased ow caused by impervious surface cover (ISC) leads to runo rates that are ampli ed by kinematic processes as they travel through the mu- nicipality's stormwater system. Elevated runo vol- umes and rates lead to high pollutant transfer and al- tered hydrology that adversely a ects urban stream ecosystems, water quality, and human health. Vegetated roof cover provides a means for re- ducing stormwater runo , while providing additional aesthetic and environmental bene ts. We tested vegetated roof plots at the Boyd Graduate Studies Building on the campus of the University of Geor- gia from October 2003 to the present for their e ec- tiveness in reducing stormwater ows. Performance results were found for a large range of storm events. Spatial analysis was performed in an urban water- shed (Tanyard Branch watershed in Athens, GA) to evaluate widespread green roof implementation. Re- sulting management scenarios are discussed.
Essential decisions for an instream flow policy

(Georgia Institute of Technology, 2005-04) Keeler, Andrew G. ; Rasmussen, Todd C.

Georgia has the opportunity to de- velop a comprehensive water management policy that meets the current and future water needs of the state and its neighbors. Incumbent upon this process is the obligation to protect the environment while at the same time maximizing the productive worth of this nite natural resource. This paper presents a set of minimum requirements for developing an instream ow policy, which is a key component of environmen- tal protection. The policy is integrally tied to the safe yield and its inherent water allocation system. Key attributes of safe yield and water allocation re- lated to instream ow policies are addressed.
Establishing the Relationship between Turbidity and Total Suspended Sediment Concentration

(Georgia Institute of Technology, 2003-04) Holliday, C. P. ; Rasmussen, Todd C. ; Miller, William P.

This laboratory work examines the relationship between turbidity (NTU) and total suspended sediment concentration (TSS, mg/L) for a Cecil Ap soil, a common Southeastern Piedmont soil type. We show a 1:1 correlation between NTU and TSS for the silt and clay fractions, but a smaller ratio for clay and bulk-soil samples. These results suggest that NTU measurements can be used to estimate sediment concentrations for fine soil fractions, but underestimates the total sediment concentration when sand-size fractions are present.
Defining a stormwater management plan: setting the stage for watershed protection

(Georgia Institute of Technology, 2003-04) Rasmussen, Todd C. ; Holmbeck-Pelham, Skelly A.

We propose a new approach to stormwater control, which we call The 10-25 Plan. The 10-25 Plan is a stormwater management framework whose goal is to prevent and mitigate the adverse economic and environmental impacts of stormwater. The framework sets a 10% threshold for impervious surfaces, above which stormwater fees are levied, with a second tier of fees that are imposed when impervious surfaces exceed 25%. Exceeding the 10% trigger would require active stormwater controls, such as the use of stormwater fees at the local level for stormwater prevention and mitigation, as well as onsite stormwater control for new and existing developments. An important priority is the establishment of Watershed Protection Areas (WPAs) in critical watersupply areas. WPAs could be acquired using stormwater fees or by using Transferable Stormwater Rights (TSRs), which are commodities that can be bought, sold, and traded - providing flexibility in meeting stormwater management goals.