6 Karst Geology and Hydrology

Thursday, 24 March 2011
8:00 AM - 12:00 PM
Room 107

A GEOCHEMICAL AND HYDROLOGICAL INVESTIGATION OF THE REDMOND CREEK KARST AQUIFER OF WAYNE COUNTY, SOUTHEAST KENTUCKY

Paper number: 6-11
Program: Theme Sessions
Time: 11:20 AM – 11:40 AM

Authors

Abstract

Geochemical and hydrological data from July 2010 through January 2010 reveal seasonal and spatial variations in the hydrology and geochemistry of the Redmond Creek karst aquifer in an undeveloped portion of southern Wayne County, Kentucky. Bi-monthly water samples and field measurements were taken from two sites: the outflow of Stream Cave in the upper reaches of the basin and just downstream of Sandy Springs, the spring hypothesized to be the primary site of aquifer discharge. Field measurements include water temperature (T), dissolved oxygen (DO), pH, specific conductance (SpC), total alkalinity (Alk), and a discharge rating curve (Q). Water samples were analyzed for the concentration of major ions (Ca, Fe, K, Mg, Na, Cl, Fl, SO4, PO4), nitrates (NO3), total organic carbon (TOC), d D and d18O, and d13C- in both dissolved organic and inorganic carbon.

Seasonal trends in the variability of water chemistry are present at both sites from late May 2010 through late November 2010. At Sandy Springs we see a drop in pH accompanied by an increase in both SpC and Alk. Over the same time period at Stream Cave pH increases, accompanied by decreasing SpC and increasing Alk. Seasonal trends are also seen in ion concentration. For example, Ca is becoming more dilute at both sites as seasonal precipitation increases.

Spatial variation is also present in the data, with water chemistry evolving from Stream Cave to Sandy Springs. Additionally, water chemistry at Stream Cave is more variable than at Sandy Springs. The pH at Sandy Springs, for example, averages 7.75 with a range of 7.1 to 7.91, compared to an average of 7.3 at Stream Cave with a range of 6.4 to 8.03. At Sandy Springs we see much higher Alk (mean = 95.36mg/L; range = 75.5 to 130.5mg/L) compared to Stream Cave (mean = 15.82 mg/L; range = 10.5 to 23.5 mg/L). SpC is also much higher at Sandy Springs (mean = 238 µS/cm; range = 197 to 296 µS/cm) compared to Stream Cave (mean = 44.69µS/cm; range = 31 to 65 µS/cm).