ASSESSMENT OF CONTAMINATION POTENTIAL OF A HIGH-YIELDING SPRING FROM FOCUSED RECHARGE OF STREAM-FLOW THROUGH SINKHOLES IN THE FLINT HILLS OF KANSAS

The goal of the Kansas Source Water Assessment Program is to identify the water sources used by public utilities that supply drinking water and to protect them from potential contamination. Crystal spring discharges at rates ranging from 28.3 to >340 L/s and is the sole source of water for a rural community in the Flint Hills region in the eastern part of the state. Very little is known about the hydrogeology of this region and in particular, the flow systems that supply ground water to the region’s many high-yielding springs. The spring is located in tall-grass prairie and the dominant land use is cattle ranching.

Crystal spring is fed by ground-water discharge from three sources moving through Permian Barneston Fm. limestones: 1) confined regional flow, 2) diffuse recharge from the Barneston outcrop, and 3) focused recharge through stream-bottom sinkholes in Martin Creek within the outcrop. Higher Cl, SO4, and SO4/Cl ratios and low dissolved organic carbon (DOC) distinguish regional flow. Recharge from diffuse and focused sources has lower Cl, SO4, and SO4/Cl ratios, but focused recharge contains much higher DOC than diffuse recharge. Nitrate in spring discharge ranges from 2 to 5 mg/L.

High-amplitude fluctuations in spring discharge are directly tied to precipitation events in the up-gradient Martin Creek drainage basin. Wetter periods and high rainfall-producing storms at other times rapidly escalate spring discharge to rates >142 L/s. Dye trace studies of the sinkholes in Martin Creek yield travel times of <43 hrs to Crystal spring 4.8 km away and suggest a well-developed conduit system in the limestone aquifer. Water-level data from monitoring wells near the sinkholes shows rapid development of a recharge mound in the adjacent aquifer during wet periods and the gradual loss of water in storage from the conduit system beneath the stream to the spring in the ensuing dry periods. Differences in the fracture/solution channel conduit system between the upper and lower Barneston may explain the apparent water-level behavior.

The primary potential source of contamination in the recharge area of Crystal spring is the pasturing of cattle. These findings do not support the need for additional measures to protect water quality at current levels of cattle grazing within the drainage basin above the spring.