STREAM TRACING IN THE BOGARDUS SPRING SYSTEM, SCHOHARIE COUNTY, NEW YORK

The Bogardus Spring system in northeastern Schoharie County, NY has three point inputs from sinking streams at Turbine Cave, Loden’s Sink and Schanz Sink. Quantitative dye tracing experiments using Uranine and Rhodamine dyes prove all three connections between insurgences and the spring. Tracing tests were carried out using automated water samplers working at intervals of fifteen minutes for periods up to about eight days. Monitoring of weirs installed at the insurgences and the spring provides data on surface input and spring flow. Tracing experiments were carried out at spring flows ranging from about 70 l/sec to about 800 l/sec. Nearly complete “elution” curves were obtained for the tests. Dye was also injected into a surface stream into which Bogardus Spring discharges.

Dye transit times decrease with increased spring flow, approximately linearly on a log-log plot. At a given flow, the average flow velocity appears to increase slightly with distance between insurgence and spring. The flow path from Loden’s Sink, which is intermediate in distance from the spring compared to the other two insurgences, appears to be less efficient than the others, as evidenced by delays in dye arrivals, especially as measured at peak dye concentrations. At very low flows the dye arrival from Loden’s Sink shows a series of peaks rather than a smooth curve. At most flows the Loden’s sink curves are broader than for traces from the other locations.

Loden’s Sink is at the bottom of a large (ca. 10⁶ liter) sinkhole that fills completely at the highest flow for which we have data. Under the conditions of our tests this led to a double peak from Loden’s, probably due to draining of the dyed water stored in the sinkhole pond after flow contributions at the spring from the other insurgences had dropped.

Dye travel time is expected to decrease at higher spring flows for simple channel flow, as is observed. The tracing results from Loden’s Sink may be explainable in terms of differences in the details of the flow path between Loden’s and Bogardus Spring as compared to the other two insurgences, including the obvious sinkhole pond that forms at high flows. Some of these details (or complexities) may often be hidden in karst drainages and contribute to complex behavior of these flow systems.