Groundwater ages and altitudes of recharge areas in the Polish Tatra Mts. as determined from 3 H, d18 O and d2 H data

Abstract

Large and medium karstic springs in the Polish Tatra Mts. occasionally sampled during low flows exhibited little scatter of stable isotope composition and distinct differences between particular sampling sites. For extreme stable isotope values of four springs, the recharge altitudes were estimated by making use of topographic and geological maps. The altitude effect found in that way served for determining the recharge altitudes of other sampled sites. The altitude-effect gradients found in that way are -0.21/100 m and -1.45/100 m for d18 O and d2 H, respectively. In general, large karstic springs (exsurgents) have the highest recharge altitudes whereas medium spring and deep wells are characterized by much lower altitudes. Tritium data interpreted with the aid of lumped parameter models yielded mean ages of ca. 3 years for low flows in large karstic springs, ca. 10 years for medium springs, and 50 to 100 years for deep wells, all with very wide age distributions. For four deep wells, the regional hydraulic conductivity estimated from tritium ages (0.8 ´ 10-6 m/s) is about 20 times lower than the geometric mean found from pumping tests (17 ´ 10-6 m/s) suggesting the existence of obstacles to regional flow.