Date of Award

12-2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Biological Sciences

Advisor

Schindler, James E

Committee Member

Colacino , James M

Committee Member

Eidson , Gene W

Committee Member

Hains , John J

Abstract

Lake James is the uppermost hydropower reservoir in the Catawba River drainage in North Carolina. The Lake James Assessment (LJA) was a descriptive study initiated between Clemson University and Duke Energy Corporation to explore the physical, chemical and biological dynamics of this oligotrophic reservoir from spring 1997 through fall 1999 (Schindler 1997). The goals of this study were to ascertain the primary drivers for the chemical dynamics of Lake James, to assess the quantities of constituents entering and leaving the reservoir, where these chemicals were incorporated within the reservoir basins, and to evaluate the efficacy of the LJA chemical budget model (LJA-CB) against traditional calculations for measures of reservoir loading and yield. I hypothesized that meteorology and lithology would be the dominant factors regulating the chemical dynamics of Lake James (Gibbs 1979, 1992). I also hypothesized that assimilation of chemical constituents within Lake James would adhere to the heuristic model of longitudinal segmentation of reservoirs of Thornton et al. (1981). I further hypothesized that the LJA-CB model based on average daily flows and monthly chemical concentrations would be more reflective of the variability in constituent loading and yield for Lake James than the traditional methods generated using average annual flows and average annual chemical concentrations (Olem and Flock 1990).
The LJA water balance (LJA-WB) and LJA-CB models were developed in the STELLA modeling environment to quantify the hydrological and chemical dynamics of Lake James. Results of the energy budget (LJA-EB) and LJA-WB generated during the period of study indicated significant water losses (approaching 20% of the total volume) from the reservoir each year with 7% attributed to evaporation and 13% to unmonitored losses. Post facto analysis of turbine losses conducted by Knight (2003) indicated losses of 1.56 m3/s (55 ft3/s) through the turbines in the Bridgewater Hydroelectric Facility (BHF), a value twice what was estimated at the time of our study (Knight 2003).
The LJA-CB was developed around the LJA-WB in STELLA as a Graphical User Interface (GUI) based modified Vollenweider (1969)/Chapra (1975 and 1979) style empirical mass balance model for an incompletely-mixed laterally-segmented reservoir with an embayment. Thornton et al. (1981) developed a heuristic model of longitudinal segmentation of reservoirs which stresses the importance of linear distance in the processing of watershed inputs into the reservoir (Thornton et al. 1981, Thornton 1990, Kennedy and Walker 1990). The LJA-CB allows for determination of lateral zones of constituent assimilation and assumes hydrology is the driving variable for the system. By summing the daily loading over a year, an annual loading estimate for each segment of the lake was calculated that was volume weighted and was used to make inferences about the spatial distribution of chemicals within the lake.
I ascertained that most of the constituent loading into the Lake James basin is derived from the Catawba River watershed (most notably the North Fork Catawba sub-watershed) and that most of the inflowing material is retained by the reservoir. I further discerned that relatively limited numbers of high flow events are responsible for providing the bulk of materials assimilated within the lake basins. I confirmed that the headwaters and upper transition zones of the Lake James reservoir have greater rates of sedimentation of most constituents relative to the lower transition and lacustrine zones and validates the model proposed by Thornton et al. (1981) and later work on spatial sedimentation of constituents and subsequent ecosystem production by Kennedy et al. (1982). However, the lacustrine station for the Linville basin is the receiving embayment for both basins and reflects the greater loading being brought in from the Catawba Basin.
I employed traditional loading calculations (Olem and Flock 1990) using monthly chemical concentrations and average daily discharge which were averaged for each year to provide a conservative estimate of loading and yield from the Lake James watershed. By comparing the LJA-CB with traditional loading and yield calculations I found that the traditional methods, in general, tended to be adequate for hydrologically driven constituents; however, biologically and redox regulated constituents do not appear to be sufficiently represented using traditional calculations of loading and yield.

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