ABSTRACT
Investigations and analysis of seepage from reservoirs and by-pass around dam sites are crucial matters in dam design. The commonly applied, standard hydrogeological models for seepage analysis and computation of possible leakage from reservoirs are of no use at many dam sites in karst. Hydrogeological singularities, in the form of karst conduits of large aperture, are the main potential leakage pathways. These features are rarely predictable from surface investigations.
The regional hydrogeological map of reservoir area should contain the following basic information: hydrogeological properties of each lithostratigraphic unit; tectonic (structural) features; estimated position of the groundwater divide with adjacent catchment areas; borehole locations; hydrological monitoring stations; listing of all of the hydrogeological features (springs, estavelles, ponors, collapses, caves, shafts, dry valleys); and results of tracer tests. Absence of large karst features at the surface (caves, shafts, sinkholes) does not mean that deep and large karstic features are not developed underground.
To evaluate the permeability of the rock mass at dam sites and reservoir banks, the Lugeon test and groundwater regime analysis are most widely applied. The Lugeon test in karstified rock is not the perfect method but it still remains the main engineering tool in dam hydrogeology.
