AN ASSESSMENT OF THE APPLICABILITY OF THE HEAT PULSE METHOD TOWARD THE DETERMINATION OF INFILTRATION RATES IN KARST LOSING-STREAM REACHES

Quantifying the rate at which water infiltrates through sediment-choked losing stream reaches into underlying karstic systems is problematic, yet critically important. Using the one-dimensional heat pulse method, we determined the rate at which water infiltrated vertically downward through an estimated 600 in by 2 in sediment-choked losing-stream reach in the Devil's Icebox Karst System of Central Missouri. The infiltration rate ranged from 4.9 x 10(-5) to 1.9 X 10(-6) M s(-1), and the calculated discharge through the reach ranged from 5.8 x 10(-2) to 2.3 x 10(-3) m(3) s(-1). The heat pulse-derived discharges for the losing reach bracketed the median discharge measured at the outlet to the karst system. Our accuracy was in part affected by significant precipitation in the karst basin during the study period that contributed flow to the outlet from recharge areas other than the investigated losing reach. Additionally, the results could be improved by future studies that deal with identifying areas of infiltration in losing reaches and how that area varies in relation to changing flow conditions. However, the heat pulse method appears useful in providing reasonable estimates of the rate of infiltration and discharge of water through sediment-choked losing reaches.