Vízügyi Közlemények, 1963 (45. évfolyam)

4. füzet - VIII. Könyvismertetés

"(33) UNDERGROUND STORAGE AND ITS APPLICATION IN SUPPLYING WATER TO BALATONALMÁDI By S. Léczfalvij, С. E. (Fort the Hungarian text see pp. 176) The waterworks for a summer resort at Lake Balaton are described. In securing the necessary water quantity extensive use has been made of underground storage. Water for the resort has been secured from a spring emerging at a distance of about 2.5 km to the NW. (Fig. 1, 2). The total annual yield of the spring is equal to the total annual demand, yet during the three summer months consumption is well in excess of the available discharge (Fig. 3). An equalizing reservoir having a capacity of 40.000 cu.m. would have been necessary, but reinforced concrete tanks of conventional design would have involved excessive costs. For this reason the water was stored underground, in the permeable, waterbearing rock of the spring itself. \ \ The method of underground storage adopted here was that referred to as sill lowering, the essential features of which are as follows: The basic aim, as with all types of storage, was to adjust the spring discharge to the fluctuating demand. Where the spring discharge is equal to the demand, the necessity of interference does not arise. At times when the spring discharge is insufficient for meeting the demand, the waterlevel of the spring is drawn down, and the water shortage is covered from the water-tilled rock interstices situated under the dynamic watersurface of the spring. A certain storage volume is thereby liberated within the rock (the magnitude of which is equal to the volume of water withdrawn). At times of spring discharges in excess of consumption, the surplus water is used to refill the storage space. Whether or not this method of storage can be realized at any particular spring depends on the prevailing geological conditions. A permeable rock layer of adequate depth below the spring sill is a prerequisite. Springs of the overflowing type belong e.g., to this category, and the one encountered here was one of them. After a brief review of theoretical problems relating to underground storage, the explorations, construction work and operating experience gained during two years are described. Explorations showed the spring to be of the overflowing karstic type, the majority of the catchment area consisting of dolomite and limestone. The spring emerges from a gravel-filled tectonic ditch collecting and draining the water of the karst in a drainlike fashion (Figs. 2, 9, 10, 11 J.The extent of depression required for securing a storage volume of 40.000 cu.m, as well as the other characteristics of the appurtenant structures have been determined by pumping tests (Fig. 12) and theoretical calculations. The structures built for the development of the spring are shown in Figs. 14 to 18. As revealed by operating tests and control measurements the development of the spring has been successful (Figs. 19 to 22). Both daily, weekly and seasonal storage could be realized. Operation during the summer season 1962 is shown in the last figure. The original natural discharge of the spring in June, 1962 was 505 cu.m/ day only, whereas daily average consumption soared to 650 cu.m. in the same month. Consequently the watersurface of the spring started to drop gradually. In August (which was the driest month during the last 120 years) consumption jumped rapidly and the average daily production from the spring attained 1050 cu.m, but peak productions of 1800 cu.m/day were also recorded. The waterlevel in the spring continued naturally to drop at an increased rate, since the natural spring discharge was no more than about 500 cu.m/day. The deepest drawdown, with a value of 4.20 m was attained on the 8th September. (The maximum possible drawdown is 4.80 m). Daily water consumption decreased to the natural spring discharge (500 cu.m/day) and even below this value, so that the spring started to recover. Storage was fully replenished by the 22nd September although the demand of the resort was fully met meanwhile. Total withdrawal from the spring during the summer period investigated attained round 58.000 cu.m, of which 38.000 cu.m was natural spring yield and 20.000 cu.m were produced from underground storage. The spring yield was thus augmented during this period by 55 per cent.