Vízügyi Közlemények, 1969 (51. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(105)into five typical groups, namely tectonic faultlines and the crushed zones accompanying them, fissures without displacement, passages along bedding planes, narrow passages by karstic dissolution, networks of cavities and caverns. The second section is devoted to pressure conditions within the karstic water mass and in this connection free-surface karstic waters and such under pressure are considered separately. At the present (beginning of 1969) data of round 300 observation wells on karstic water arc filed at the Research Institute for Water Resources Development, Budapest. The factors controlling the dynamics of free-surface karstic water are as follows: infiltration and natural drainage, surface topography, geological structure, long-term meteorological periods and tidal phenomena in the earth crust. Pressure conditions in karstic waters under pressure are influenced by changes in hydrostatic pressure, the temperature and chemical composition of water. However, the predominant factor affecting changes in both water surface and pressure is human influence, i.e. the withdrawal of water for human usage. The karstic water hydrograph for natural conditions and for an area with artificial withdrawal is shown in curves "a" and "b" of Fig. 5, respectively. The hydrograph of the karst water table in a region of the Transdanubian Central Range is shown in Fig. 6 before (1959) and three years after the commencement of mine drainage. The results of investigations into the recharge conditions of karstic water are described in section 3. A method is presented for determining the water volume recharged from precipitation. The determination is aided by the graph illustrated in Fig. 8. The determination of the "infiltration index" for different rocks is described with reference to Fig. 9. The method introduced for filing water withdrawal is described in the fourth section, pointing out that 15-year long records are available for more than 1000 springs, whereas records extending to more than 8 years have been kept at 200 locations on water production by mines and water works. Studies and experiments concerned with the flow of karstic water are described in the fifth section. Pressure and flow conditions resulting from withdrawal from a karstic water body are exemplified in Fig. 10 whence it is to be seen that by pumping at several points from the same network of fissures different influence regions are developed within the same depression space. Subsequently the experiments are described which have been performed to study flow conditions in a karstic network of fissures using different models, together with the laboratory studies performed at the Research Institute of Water Resources Development on an imaginary fissured rock model to study the influence of forces affecting flow at different fissure widths. REINFORCEMENT OF FLOOD LEVEES AT LOWEST COST By Dr. Bogárdi, I. Civ. Eng. For the Hungarian text see pp. 499) Together with Z. Máthé as co-author a paper has been published by the author in No. 4, 1968, of "Hydraulic Engineering" under the title: "An investigation into the degree of protection offered by flood levees and the economical improvement thereof using stochastic methods". The present short paper is based on the principle of the degree of protection and its distribution function introduced earlier 1

1] describing a procedure with the help of which any particular initial degree of protection can be improved to a specified value at lowest cost, i.e. at the optimum cost-benefit ratio. Flood control development on national level must be implemented by the optimum use of available funds. Development cannot be optimum unless the individual sub-policies are also devised for highest economic efficiency. Subpolicies of this type are arrived at by the procedure suggested. In earlier practice flood levees have frequently been reinforced to a uniform typical cross section, and no allowance has been made for the hydrological, hydraulic,