Vízügyi Közlemények, 1973 (55. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(40) tant for the thorough assessment of the efficiency of treatment and the effectiveness of assimilation alike. f) Adopting as the basis of considerations the wastewater discharged at Budapest actually (Table IV) and as estimated for 1986 (Table VII), further using the available data on changes in BOD

5, the necessary removal efficiency has been estimated in terms of BOD

5. The statistical evaluation has shown this value to be 85%, in order to attain the limit concentration of 5 mg/lit with a probability of 95% at the southern border of the country ( Fig. 9). g) Accepting as a guideline the 85% removal efficiency desired for BOD

5, the corresponding values have been checked for the other components of water quality (Fig. 10, Tables VI, VII and VIII

). In view of the present data on assimilation the results were found acceptable, but after 1980, when the construction of the barrage at Adonv will become justified, higher efficiencies will probably become desirable. The financial consequances of all these measures have also been examined with the result ( Figs. 11 and 12) that if three treatment plants are constructed, each of round one-third million cu. m/day capacity, the investment costs will amount to 2.7 thousand million Forints, while two plants, one of 0.5 million and one of 1 million cu. m/day capacity, would call for 2.55 thousand million Forints of investment. IBRIGATION IN BULGABIA By Gábri, Mihály, Civ. Engr. (For the Hungarian text see pp. 192) On the occasion of the congress of the International Commission on Irrigation and Drainage (ICID), in May, 1972 in Varna (Bulgaria), the author was given opportunity to study the present situation of irrigation farming in Bulgaria. In Chapter 1 a brief review is presented on the natural conditions in Bulgaria. In the distant future irrigation will prove economically feasible over about 75% of the total arable area in the country ( Fig. 1 ). In Chapter 2 data are given concerning water resources and water uses. In 1967, 2.8 million cu.m water was used from surface supplies, 488 million cu.m from the Danube and 824 million cu.m from subsurface supplies. Of the total consumption 64% were used for irrigation. The river discharge is 19,400 million cu.m/year. 82% of the water is available at great distances from the arable lands. The subsurface freshwater supplies available are 3,000 million cu.m per year. At present irrigation-drainage facilities have been installed over 22% of the cultivated area. Information on the sources of irrigation water is given in Fig. 2. Altogether 4,860 million cu.m of water are stored behind 638 medium and large, further 1,377 small dams. Of this volume 3,000 million cu.m serve the purposes of irrigation. The largest dam is the Taonevo dam ( Fig. 3). Of the existing 2,400 irrigation pumping stations the "Lyulyaka" plant is the largest / Fig. 4). The methods of irrigation are reviewed in Table I. As will be perceived from the data in Fig. 5 and Table II, 75% of all irrigations will be by the sprinkler method in 1975. In Chapter 3 the role of the Danube is considered. The average rate of flow is 6,330 cu.m/sec, corresponding to a runoff volume of 184,000 million cu.m/year. In the distant future 843,000 hectares will be irrigated from the Danube. In Chapter 4 the design details of automatic irrigation processes are described, as used in the irrigation plots with fully buried distribution networks. This systems is used in vineyards, orchards and hop-fields. At the Institute for Hydrotechnics and Melioration in Sofia two types of automatic, telescopically rising sprinkler hydrants have been developed. These are illustrated in Figs. 6a and b. One method of irrigation from permanently installed networks has been evolved by I. Varlev, using portable rigid, or flexible pipes (Fig. 7). Surface irrigation by automatically moving hydrants is illustrated in Fig. 8. In Chapter 5 the major irrigation projects are described. The number of these projects is 85 and their area increases by 40 000 hectares annually. Of the total area equipped for irrigation 64% pertain to large state-owned farms. The location of the