Hidrológiai Közlöny 1962 (42. évfolyam)

2. szám - Ubell Károly: A felszín alatti vízkészlet

104 Hidrológiai Közlöny 1962. 2. sz. Ubell K.: A ielszin alatti vízkészlet B BeHrpiiH HerjiyöOKHe rpyHTOBbie boau nonojiHHIOTCH nepHOfliiMecKii B RO/;y H3 ocaAKOB B OÖTEME npHÖJi. 70,230 MUAAIIOHOE M

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3/BOÖ, T. e. 40 M

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3/cei<. y apTe3iiaHCKiix cjioeB HaM eme Hen3BecTHbi xapaKTep n Mepa npiiTOKa. HacToamee B0A0n0jib30BaHiie coCTaBJlHCT 7—8 M

s/cei<. y 3THX CJ10CB nOJIHOCTblO MOHCHO ÖblJIO 6bl HCn0Jlb30BaTb, T. e. npOH3BOAHTb npHTOKH H 3T0 npcACTaBJiíiJio űbi coöofi BepxHiiií npeAeji, HO B03HiiKaeT H Bonpoc, MTO BO MHOTHX CJiyMaflX IipilTOKa 11 HCT, Mbl noTpeőjiHeM HaKOiuieHHbift 3a HecKOJibKO TbiCHMHJieTiiíí 3anac BOÁM. Ground Water Resources By Dr. K. übell Candidate of Technical Sciences A few years ago the problem was rather to locate water, than to determine the available quantity thereof. The solution of the former is made possible by the knowledge of the position in space and of the physical properties of the aquifers, i. e. by an exploration of the possible methods of obtaining water. The problem to be faced today is mostly the determination of the water quantity that can be withdrawn and the period for which a certain amount can be withdrawn without exhausting the supply. For this purpose information on the variations of groundwater, i. e., on the waterhousehold thereof must be made available. As far as water resources are concerned distinction can be made between a so called static supply, to be understood regardless of movements, the amount of water defined by the volume of water filling the voids in the soil, and the moving or dynamic supply. Founding on the svstem developed in the Soviet Union for classifying water resources (9, 10), the author wishes to complete the above grouping by the following. significant portion (about 80 to 90 per cent) of the static supply does not participate in the natural hydrological cycle. This portion forms the passive resources, which receive no recharge. This assumption appears to be justified to the author on the basis of experiments carried out recently by using triaxial pressure cells. It is concluded therefrom, that below a certain depth in loose sedimentáry rocks, the stress due to the weight of the overlying layers is carried simultaneously by water and the solid particles, and water does not move in the voids until this state of stress is disturbed by boring (16). As a consequence of this approach the separation of the passive supply from that participating in the hydrologic cycle would appear as the most important problem. As far as methods are concerned, a complex waterhousehold investigation including the results of geological, geomorpliological, soil mechanical, hydrological and hydraulic studies, is felt to be suitable. According to present knowledge the groundwater resources of Hungary are charactcrized by the following features : The totál volume of water filling the voids of fissured and loose sedimentáry rocks, the static supply may be estimated at about 5000 x 10

9 cu. TO. Data on water excliange at the surface are compiled in Table 1. An equiíibrum is revealed thereby without including the changes in groundwater resources. The recharge of karstic waters is an exception to this, which returns to the surface through karstic springs and represents a discharge of 10 cu-m/sec on the average. Data on present water consumption can be found in Table 2. Present withdrawal from groundwater resources is still too small to permit any far reaching conclusions to be drawn from a comparison of quantities. About 350 millión cu. m are consumed annually from groundwater resources. This is only one-tenthousandth part of the static supply and 0,6 per cent of the annual precipitation volume. For assessing the water quantity that can be withdrawn, the process of replenishment must be explored. The main source of water to recharge groundwater is precipitation. Recharge from precipitation may be due to local precipitation, or to such falling on an outer area, on the principal recharge area of the aquifer. For assessing infiltration and, corrolary to this recharge, observation of fissured, fragmented rocks communicating with the surface, and of shallow groundwater is of paramount importance, since replenishment of the entire resources is possible over these only. The difference between recharge from precipitation through fissured rocks and the phenomenon taking place in loose sedimentáry rocks is essential (Fig. 1.). The former results always in an extended increase of storage, provided precipitation is in excess of momentary evaporation. The average value of utilizable recharge can be determined from the accumulation thereof, and this is represented for the karstic regions in Hungary by the value of 10 cu. m/sec. With loose sedimentáry soils, if totál precipitation does not exceed the value F

0 obtained by Penman's formula, i. e. 80 per cent of potential evaporation, only periodical recharge (Fig. 1.) occurs in the season, where the cumulative totál of precipitation is in excess of evaporation but this water evaporates again in summer, when evaporation is stronger (Table 3.). The characteristic features of the annual exchange in shallow groundwater, which depend on the depth of the groundwater table, are illustrated in Fig. 3. An extended increase in resources does not occur unless the annual precipitation volume exceeds 80 per cent of Penman's E

0 value. (Fig. 2.) The periodic annual recharge to shallow groundwater from precipitation is about 10 230 millión cu. TO in Hungary. This volume, however, is exhausted even without withdrawal by natural consumptive í'actors, primarily evaporation. At present only the part participating in lateral flow is regarded as utilizable from this quantity. Relying on observation data the volume thereof is estimated at 1261 millión cu. m/annum, i. e., at 40 cu. m/sec. Compared with this the rate of utilization is at present from 4 to 5 cu. m/sec. The nature and extent of recharge to artesian aquifers are unknown as yet. Utilization at present is at the rate of 7 to 8 cu. m/sec. The recharge to these layers could be utilized fully and this would present the upper limit value, but the thought may occur, that in many instances tliere is no recharge at all, and the water resources accumulated during thousands of years are depleted.