Publication Date

5-2014

Advisor(s) - Committee Chair

Chris Groves (Director), Jason Polk, Fred Siewers

Degree Program

Department of Geography and Geology

Degree Type

Master of Science

Abstract

Kentucky’s Upper Green River Basin has received significant attention due to the area’s high biodiversity and spectacular karst development. While carbonate bedrock is present throughout the watershed, it is more extensive and homogenous along the river between Greensburg and Munfordville than upstream from Greensburg where the geology is more heterogeneous. This research quantitatively evaluated how lithological differences between the two catchment areas impact hydrochemistry and inorganic carbon cycling. This first required correcting catchment boundaries on previous US Geological Survey Hydrologic Unit Maps to account for areas where the boundaries cross sinkhole plains. Basin boundaries using existing Kentucky Division of Water dye trace data differed from the earlier versions by as much as three kilometers. The river at the downstream site is more strongly influenced by carbonate mineral dissolution, reflected in higher specific conductance (SpC) and pH. The SpC at Munfordville ranges from 0.9 to 4.8 times that at Greensburg, averaging 2.0 times higher. Although rainfall is impacted by sulfuric acid from coal burning, river pH is buffered at both sites. The pH is higher at Munfordville 91% of the time, by an average of 0.28 units. Diurnal, photosynthetic pH variations are damped out downstream suggesting interactions between geologic and biological influences on river chemistry. River temperature differences between the two sites are at least 4oC higher at Greensburg under warm season conditions, but there is a clear trend of temperature differences diminishing as the river cools through the fall and winter. This results from a relatively stable temperature at Munfordville, impacted by large spring inputs of groundwater within the karst region downstream. Although weak statistical relationships between SpC and HCO3 - create uncertainties in high resolution carbon flux calculations, measurement of these fluxes is more highly impacted by discharge variations than concentration variations, which resulted in average daily atmospheric flux estimates within 34% between the two basins using weekly concentration data (3.3x108 vs. 2.2x108 gkm-2 d-1, where km2 is the outcrop area of carbonate rocks), and within only 12% using 15-minute concentration data from regressions (2.6x108 vs. 2.3x108 gkm-2 d-1) for Greensburg and Munfordville, respectively.

Disciplines

Geochemistry | Geography | Hydrology | Physical and Environmental Geography

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