CRYSTAL SPRING: A WINDOW INTO THE HYDROGEOLOGY OF THE FLINT HILLS REGION OF KANSAS

Crystal spring is a high discharge spring located in the central part of the Flint Hills region of Kansas and during a two-year field study, measured discharge ranged from <28.3 L/s to >510 L/s. The near-surface geologic units consists of alternating Permian Chase Group limestones and shales and the primary aquifer zones are in the 24.4 m thick Barneston Limestone. Ground water moves in a southerly direction from the upland area toward Crystal spring and the Cottonwood River. Water levels in a monitoring well installed in the Barneston Limestone aquifer 213 m away from Martin Creek fluctuated over a 10 m interval and were low during extended dry periods, and high during wet periods.

Within its catchment ground water moves through an integrated network of fractures (aperture widths up to several millimeters) and conduits (up to a meter or more in diameter) in the Barneston Limestone to Crystal spring. Rapid entry and movement of ground water toward the spring is facilitated by sinkhole-like openings in the streambed of Martin Creek, approximately 4-4.8 km north of the spring. Dye-trace experiments conducted during a relatively dry period indicated travel times through the ground water system of approximately 60 hrs from the sinkholes to the spring, a travel velocity of approximately 1.5 km/day.

Spring discharge water quality reflects geochemical interactions between the ground water and limestone aquifer mixing with recharge from precipitation events as shown by geochemical mixing curves. Calcium and bicarbonate dominate the dissolved ionic constituents. Dissolved solids ranged from 311-410 mg/L in samples of Crystal spring collected during 2002 water-sampling events. Suilfate, chloride, and nitrate ranged from 12 - 42.4 mg/L, 4.5 - 8.5 mg/L, and 2 - 9 mg/L, respectively in 15 monthly samples collected from the spring.

The relationships between precipitation events and spring discharge, turbidity, and chemistry, precipitation and water levels in the aquifer near Martin Creek, and the short travel time between the sinkholes and the spring indicate that the creek is a major contributor of water to Crystal spring during wet periods. The other major contributor is the drainage from the part of the aquifer where the solution openings are small scale and less well connected. This source sustains spring discharge during drier periods.