Using Multivariate Analysis of Geochemical Data to Better Define Hydrologic Interfaces in Surface Water - Groundwater Systems
Date of Award
Master of Science
Chris Cox, John Schwartz
Groundwater-surface water interactions have been shown to be important to flow generation and stream chemistry in upland catchment environments. These areas, however, are often difficult to access making the implementation of standard hydrological surface and subsurface monitoring equipment and characterization procedures impractical, arduous and in many cases impossible due to the nature of the terrain and also regulatory guidelines for protected areas. By collecting surface water samples at distinct water contribution sites to a headwater stream, areas of groundwater influence were inferred and a hydrochemical conceptual model of a small basin was created.
The objectives of this research were to 1) understand the groundwater chemistry influences to an upland stream in the Great Smoky Mountains National Park (GSMNP) using limited surface water data 2) determine if the use of multivariate statistics could help delineate water interaction “types” within the study basin, 3) create a conceptual model to define the chemical interactions in the stream using a comparison of data. The objectives were met by the analyses of field data collected within Ramsey Prong, a remote forested, high elevation stream in the Middle Prong Little Pigeon River Watershed chosen for the study site. Eight sampling sites were selected at hydrologic and hydrochemically significant points in the basin. Three data collection trips were performed in April, July, and August of 2007. Water sampled for analysis of cations, anions, and trace metals was collected and flow measurements were recorded on each trip at each site.
Multivariate analyses were conducted on the collected data to detect correlations between parameters that might indicate similar chemistries or water interaction “types” where high correlations were displayed. Three water types: 1) surface water; 2) spring water; and 3) a top of catchment mixture of spring and highly acidic deposition and drainage water were delineated. Spring 1, located at the bottom of the study area, was designated as the first water type and displayed high concentrations of Si, Na, ANC, and pH. The source of this water was affirmed by groundw32ater characteristics caused by the sandstone subsurface environment. The second water type, consisting of the two highest elevation sample sites, displayed characteristics of acid deposition and acid-rock or acid induced leaching including, low pH and ANC and high levels of SO4, Mn, Fe, and Al ions. Increased levels of Si and Na also suggested groundwater interaction further up the sampled tributary. Water designated as the third water type consisted of the remaining in-stream samples which demonstrated a trend of general dilution in most atmospherically input ions and a concentrating of geochemical parameters. Large areas of focused recharge signatures were not detected in the study area leading to the assumption of primarily diffuse recharge throughout the stream. Two tributaries sampled on the August collection date displayed groundwater chemistries with a different signature than that of the stream and showed indications of water quality buffering. The analysis demonstrated the possibility for influential stream buffering in the GSMNP by groundwater and groundwater sourced inputs and also the importance of groundwater in this system.
Owen, Candice Ann, "Using Multivariate Analysis of Geochemical Data to Better Define Hydrologic Interfaces in Surface Water - Groundwater Systems. " Master's Thesis, University of Tennessee, 2007.