Geothermal‐Water Characteristics in the Surdulica Aquifer

Abstract

The Surdulica‐Bujanovac geothermal region of southeastern Serbia, with granodiorite (Surdulica) and granite (Bujanovac) aquifers (water temperatures of 125°C and 46°C, respectively) was hydrogeologically and geochemically studied using environmental isotopes from 1986 to 1990. In the Surdulica system, water, rock, and vegetation samples from 35 locations (springs, rivers, and boreholes) representing all parts of the hydrogeological system (recharge area, transition zone, and terminus with hot deep‐circulated waters) were collected for geochemical and isotope analyses (D, 18O,3H, 13C, 14C). From the recharge area to the terminus of the system, ground‐water temperatures and ionic concentrations increase two to three orders of magnitude: temperature from 3–126°C, Na+ 2.3–1127 mg/1; HCO3− 30.5–2989 mg/1; SO42− 4.8–480 mg/1; SiO2 3–90 mg/1. The hot waters, appearing at the terminus of the system (Vranjska and Bujanovac Spas locations) are the oldest, based on 14C and 3H. The δ13C attains the low negative value of −0.4‰ for hot waters, approaching those in the aquifer matrix, which are in the range between −8.4 and + 2 ‰. The δ18O and δD values in precipitation and ground water indicate that recharge takes place predominantly at the higher elevations (more than 500 m asl) and in the cold seasons. A dual‐porosity system comprised of fissures and intergranular storage controls fluid transport. The deepest flows are hydraulically isolated from fresh waters. Low 14C contents (1–6 pMC) and the absence of3 H suggest the mean residence times for the older water up to 20,000 years. A 18O shift and chemical geothermometers suggest that their base temperatures of more than 200°C are not likely.

Surveying Ground Water Level Using Remote Sensing: An Example over the Seco and Hondo Creek Watershed in Texas

“…In general, it takes a long time, several weeks to years, for surface water to permeate through soil layers and rock formations and to replenish the aquifer. Studies related to ground water recharge normally used monthly to annual precipitation data (e.g., Hadzisehović et al 1995;Ginting et al 2000). The results of this study indicate that local precipitation did not notably affect ground water levels within 10 d in the study area.…”

“…Studies related to ground water recharge normally used monthly to annual precipitation data (e.g., Hadzisehović et al 1995;Ginting et al 2000). Studies related to ground water recharge normally used monthly to annual precipitation data (e.g., Hadzisehović et al 1995;Ginting et al 2000).…”

Hydrogeothermal characteristics of groundwater from Ribarska Banja spa, central Serbia

“…Jastrebac within K-Pg contact metamorphic rocks. This is also confirmed by the low concentrations of 18 O and 2 H because low isotope concentrations are related to waters recharging in the winter months at high attitudes (HADŽIŠEHOVIĆ et al 1995;KEBEDE et al 2005).…”