Publication Date

8-1-2006

Degree Program

Department of Geography and Geology

Degree Type

Master of Geoscience

Abstract

This study uses high-resolution, long-term conductivity, temperature, discharge, pH, and laboratory data from 2001 through 2003 from an alpine karst spring located at 2,500 m amsl in Sequoia National Park, California to reveal detailed chemical parameters of this karst system. The data show a system with a pronounced spring run-off, extended periods of base flow quiescence, storm responses tied to precipitation as rain or as snowfall, and clear diurnal and seasonal patterns of discharge. pH and spC values show an inverse relationship to discharge and temperature, which are generally in phase. Total inorganic carbon (TIC) and the fraction of mineral-derived and biologically derived C were calculated using three methods. One provided values close to the theoretically likely ratio of 50:50 between the two C sources, while others showed ratios of greater biologically derived C, an unlikely possibility in groundwater chemistry. Saturation indices for the system vary seasonally, with base flow waters saturated at SI values between 0.2 and 0.5, and spring run-off (Q > 100 L/s) waters under saturated and chemically aggressive with SI values as low as -1.2. Late summer rain storm events can return the system to an under saturated state. The denudation rate for the marble bedrock, which makes up approximately 8% of the basin, was found to be high at 148.6 mm/1000 years. Ion and TIC flux are shown to be determined by discharge and not ion concentration.

Disciplines

Geology

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