Georgia Water Resources Conference

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Georgia Water Resources Conference

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https://hdl.handle.net/1853/70886

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Georgia Water Resources Institute

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Now showing 1 - 10 of 32

Declaring Drought for Effective Water Management

(Georgia Institute of Technology, 2013-04) McKay, S. Kyle ; Rasmussen, Todd C.

Water managers are tasked with resolving conflicts between freshwater resource uses, which range from municipal water supply, to recreation, and to sustaining aquatic ecosystem integrity. Further complicating management, hydrologic processes experience numerous sources of periodic, quasi-periodic, and episodic variation. Water allocation tradeoffs are often most complex and contentious when availability is low. Drought is a “recurring extreme climatic event over land characterized by below-normal precipitation over a period of months to years” (Dai 2011). Water managers often apply indicators of climatologic and hydrologic conditions to identify when drought conditions are reached (e.g., Palmer Drought Severity Index, streamflow, respectively). These indicators inform drought declarations, with associated drought responses such as watering restrictions. Herein, we suggest techniques for predicting and declaring oncoming drought to improve the accuracy of drought declarations. We hypothesize that drought indicators in preceding months are predictive of future drought levels. Specifically, we develop predictive models using the Palmer Hydrologic Drought Index, a common drought indicator. We then demonstrate the utility of our model for drought declarations for the Middle Oconee River near Athens.
Coupling Tritium Release Data with Remotely Sensed Precipitation Data to Assess Model Uncertainties

(Georgia Institute of Technology, 2011-04) Avant, Brian K. ; Ignatius, Amber R. ; Rasmussen, Todd C. ; Grundstein, Andrew ; Mote, Thomas L. ; Shepherd, J. Marshall

An accidental tritium release (570 L, 210 TBq) from the K-Reactor at the Savannah River Site (South Carolina, USA) occurred between December 22- 25, 1991. Observed tritium concentrations in rivers and streams, as well as in the coastal estuary, are used to calibrate a hydrologic flow and transport model, BASINS 4.0 (Better Assessment Science Integrating Point and Non- Point Sources) environmental analysis system and the HSPF hydrologic model. The model is used to investigate complex hydrometeorological and source attribution problems. Both source and meteorologic input uncertainties are evaluated with respect to model predictions. Meteorological inputs include ground-based rain gauges supple-mented with and several NASA products including TRMM 3B42, TRMM 3B42RT, and MERRA (Modern Era Retrospective-Analysis for Research and Applications) reanalysis data. Model parameter uncertainties are evaluated using PEST (Model-Independent Parameter Estimation and Uncertainty Analysis) and coupled to meteorologic uncertainties to provide bounding estimates of model accuracy.
Beyond Correlation: the Search for Causal Relationships Between Flow Percentiles and Watershed Variables

(Georgia Institute of Technology, 2011-04) Ssegane, Herbert ; Tollner, E. W. ; Mohamoud, Yusuf ; Rasmussen, Todd C. ; Dowd, John F.

The study explored use of causal feature selection algorithms to select dominant watershed variables that drive high, medium, and low flows. A two step approach was implemented. The first step minimized variable redundancy by examining variable relevance, variable redundancy, and conditional relevance of variable pairs whose correlation was greater than 0.9. The second step used six algorithms that seek to reconstruct a Bayesian network structure around a target variable for each flow percentile. Nineteen (19) flow percentiles were used to characterize high, medium, and low flow conditions of 26 Piedmont watersheds in the Mid-Atlantic. The algorithms included: (1) Grow-Shrink (GS); (2) interleaved-Incremental Association Markov Boundary (interIAMB) (3) Incremental Association Markov Boundary with Peter-Clark (IAMBnPC); (4) Local Causal Discovery (LCD2); (5) HITON-PC; and (6) HITON-MB. A new method was developed to quantify the reliability of each algorithm and its performance was compared to existing reliability methods. The effect of the initial number of variables on the final variable set selected by each algorithm was tested. Fusion of the algorithms was used to determine the overall dominant features for each flow percentile.
Hydrologic Impacts of Energy Production

(Georgia Institute of Technology, 2011-04) Rasmussen, Todd C.

Global future energy requirements will likely require substantial investments in power production facilities. Both hydro- and thermo-electric power production require water as part of their operations, some of which is water consumptive (i.e., water is lost by evaporation as part of the cooling or storage process), while other water use is nonconsumptive (i.e., water is returned to the source). Both consumptive and non-consumptive water uses may affect water quantity and quality, such as increased thermal load, decreased hydrologic connectivity, and alteration of natural flow regimes. This presentation discusses the main features of the water-energy nexus with the goal of establishing a framework for evaluating the hydrologic impacts of energy production.
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.