Abstract
Two tracer tests were carried out in the Huber sink in the village of Krystofovo Udolf near the city of Liberec, northern part of the Czech Republic. The aim of tracer testswasto verify the flow direction and to characterize the flow and karst conduits.
Small lenses of crystalline carbonates are enclosed in quartzite and phyllite in the area of Krystofovo Udolf. Local karst springs were turned in a water supply network for the Liberec city in 1920, and the Huber sink was sealed to avoid contamination. n 1970s, the existing water supply system was abandoned, and in 1990s the seal of the sink was removed and the stream was reactivated.
Two water works were constructed downstream, and further in the text are called the upper (HV) and the lower (DV), see Fig. 1. The water from HV flowsthrough pipesto DV.
Besidesthe water worksthere isan abandoned mine with a small outflow of mine water (OD) in the area. Two tracer tests were performed in the Huber sink, using kitchen salt asa tracer.
Tracer concentration wasmonitored using electric conductivity metersequipped with data loggers(WTW and Solinst deviceswith conductivity valuescompensated to con- stant temperature). Discharges of the sink and springs were mea- (03-13 Hrádek nad Nisou) sured by filling the vessel, and by dilution method.
A Qtracer2 program (Field 2002) was used for analysis of tracer- break- through curve. Quantitative tracer tests showed that water from sink flows into HV (Figs2-5).
The first arrival time wasabout 5 hours. Maxi- mum velocity was 3 cm/s, mean flow velocity 0.7-1 cm/s.
The vol- ume of karst conduits was found to correspond to 34-430 m3, the mean flow area wasbetween 0.07-0.8 m2. Dispersivity was found to be surprisingly high (50-170 m), which indicates that karst conduits are probably filled with detritus, or due to large changes in flow cross-sectional area.