Masters Theses

Date of Award

12-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

R. Bruce Robinson

Committee Members

James L. Smoot, Kevin Robinson

Abstract

Park-wide water quality monitoring has consisted of quarterly sampling of 90 stream sites within the Great Smoky Mountains National Park (GRSM) and analyzing for pH, acid neutralizing capacity (ANC), conductivity, major cations, and major anions. The sites are distributed throughout the GRSM to include the following watersheds: Abrams Creek, Bunches Creek, Cataloochee Creek, Cosby Creek, Hazel Creek, Indian Camp Creek, East Prong Little River, Middle Prong Little River, West Prong Little River, Middle Prong Little Pigeon River, West Prong Little Pigeon River, and Oconaluftee River. Sampling sites range in elevation from 335 to 1,679 meters above mean sea level and include drainage basins with areas which have been disturbed, primarily undisturbed, underlain by different geologic formations, and covered by different vegetation types. Park-wide data collected from October 1993 to October 1998 were analyzed to describe spatial variability, temporal trends (seasonal and long-term), and influences of basin characteristics on water quality. Multiple linear regression methods were used to explain median water quality constituent values using basin characteristics obtained from topographical maps and a GIS database. Much of the variability in water quality constituent values is explained by sample site elevation. Significant elevation trends exist (p<0.05) for pH, ANC, nitrate, sodium, and potassium. Values for pH, ANC, sodium, and potassium decrease with increases in elevation. Nitrate concentrations increase with increases in elevation. Sulfate concentrations increase with elevation but the trend is not as significant (p<0.10). Seasonal trends are statistically significant for pH, ANC, conductivity, nitrate, chloride, potassium, and sodium. Values for pH, ANC, chloride, sodium, and potassium are higher during the drier times of the year (autumn). Nitrate concentrations are the highest during the winter. Sulfate does not show seasonal differences. Time trend analysis by linear regression modeling reveals a statistically significant decreasing trend in normalized pH over time. The time required for the upper elevation streams to become more acidic and approach critical pH values appears less than that required for lower elevation streams. If conditions remain the same and past trends continue, the model suggests that sampling sites between 1,524 and 1,676 meters above mean sea level may have pH values less than or equal to 5.50 within only four years and less than or equal to 5.00 within only 11 years. At the lower elevations, between 305 and 457 meters, sampling sites may have pH values less than or equal to 5.50 within 46 years and less than or equal to 5.00 within 67 years. The models used to predict future values of pH in sampled surface water explain an average of 12% of the variability in the data. This means that an average of 88% of the variability is unaccounted for by the models. Unexpectedly, normalized ANC does not show the same decreasing trend over time as normalized pH. Results of time trend analysis for conductivity, nitrate, and sulfate are less conclusive. Basin characteristics explain much of the variability in water quality constituent values. The adjusted r-square values for the models range from 0.55 to 0.98. The results presented offer hope for using basin characteristics and stepwise multiple regression to predict water quality in unsampled and forested areas like the GRSM. Regression analysis demonstrates that two geologic formations. Limestone and Anakeesta, exert a significant influence on water chemistry in sampled basins. Also influential to water quality is the past disturbance history within the sampled basin, particularly the percentage of the basin which has not been disturbed by logging or settlement prior to establishment of the GRSM.

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