Andrew J Peters

Classification of Thermal Patterns at Karst Springs and Cave Streams

Thermal patterns of karst springs and cave streams provide potentially useful information concerning aquifer geometry and recharge. Temperature monitoring at 25 springs and cave streams in southeastern Minnesota has shown four distinct thermal patterns. These patterns can be divided into two types: those produced by flow paths with ineffective heat exchange, such as conduits, and those produced by flow paths with effective heat exchange, such as small fractures and pore space. Thermally ineffective patterns result when water flows through the aquifer before it can equilibrate to the rock temperature. Thermally ineffective patterns can be either event-scale, as produced by rainfall or snowmelt events, or seasonal scale, as produced by input from a perennial surface stream. Thermally effective patterns result when water equilibrates to rock temperature, and the patterns displayed depend on whether the aquifer temperature is changing over time. Shallow aquifers with seasonally varying temperatures display a phase-shifted seasonal signal, whereas deeper aquifers with constant temperatures display a stable temperature pattern. An individual aquifer may display more than one of these patterns. Since karst aquifers typically contain both thermally effective and ineffective routes, we argue that the thermal response is strongly influenced by recharge mode.

Spring Characterization Methods & Springshed Mapping

A summary of springshed delineation techniques using the integration of historic dye tracing information, borehole geophysics and chemistry measurements. Fountain, Mahoney, Waterhole, Wykoff, Starless River and Cold Spring springshed delineations included. Interpretations are subject to change as new traces and information becomes available. A collaborative effort between the University of Minnesota and the Department of Natural Resources.

Dye tracing within the St. Lawrence confining unit in Southeastern Minnesota

A single trace near the Fillmore-Winona County Border near the City of Rushford, Fillmore County, Minnesota. The trace began in Winona County and did not cross the county boundary. Primary goal of the study was to delineate the springshed feeding a cluster of trout streams. A collaborative effort between the Minnesota Department of Natural Resources and the University of Minnesota.