Vízügyi Közlemények, 1969 (51. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

(101) THE IMPACT OF URBANIZATION ON WATER RESOURCES MANAGEMENT By Dr. Lászlóffij, W. (For the Hungarian text see pp. 435) The problem mentioned in the title is analysed in ten chapters according to the following subdivision: 1. The process of urbanization. The trend towards the accumulation of people in towns of growing size is a phenomenon accompanying technical development. Whereas the number of towns with population figures exceeding the 1 million limit was no more than 11 at the beginning of the century, this number increased by now to 127 and vast centers called "megalopolis" are in the course of development. The ratio of population living in towns is expected to increase from the present 20% to 50% by 2000. This trend can be observed in Hungary as well. Budapest with almost 2 million inhabitants accomodates 19.4% of the country's population, whereas 25.2% live in the five towns with more than 100,000 inhabitants (Table I.) The population in towns of an industrial character grows at a rate far in excess of the national average (Fig. 1). 2. Changes in the urban water demand. The first and often limiting feature of urban development is the high water demand which occurs furthermore in a concentrated form. Besides the number also the demands of the population tend to increase. The per capita consumption in luxury apartments attains as much as 300 litre per day. As to be seen from Table II in the smaller towns of Hungary 18 to 38% of the apartments built between 1938 and 1940 include a bathroom, whereas between 1960 and 1963 this ratio increased to 81 — 96%. With proceeding urbanization both industrial and municipal consumption as well as water losses increase proportionately and these can be expressed as percentage of the total consumption ( Table III

). In the final count the production of water works is seen to increase from year to year and this trend can be characterized by an exponentially increasing curve (Fig. 2.). 3'. Sources of water supply. Owing to the steadily increasing demand large cities are compelled to rely on increasingly distant sources of supply. (A few extreme values are quoted in the Hungarian text.) Even in Hungary some towns are supplied from sources lying at a distance of 40 km. The difficulties in supply may give rise to serious conflicts between interested towns. Surface supplies must be relied upon, which frequently entail quality problems. In some instances bottled mineral waters are preferred in spite of their higher price. The increasing withdrawal of subsurface supplies is accompanied by the considerably sinking of the water table (Table IV.). For example in Debrecen the depression attained 20 to 25 m. As an unwanted corrolary phenomenon settlement of the terrain may be observed. This occurred to a slight extent in Hungary where a settlement of 53 mm was observed in the course of 40 years in the vicinity of the Debrecen waterworks. Production is not always capable of keeping pace With increasing demands, as a result of which w'ater shortage is a common phenomenon in large towns which may become even more severe where the storage capacity is low. Potential supplies for large towns must be studied intensively with due allowance to every possible set of conditions for adjustment to changing circumstances. 4. Wastes disposal. Most of the water consumed appears in the form of wastes the continuous disposal of which must be solved. Wastes are produced in Budapest in dry weather at the rate of 10 cu.m per sec. 1:500 dilution considered allowable in earlier textbooks is no more statisfied at low discharges of the recipient. In the case of biologically treated wastes the required minimum rate of dilution is 1:8. This requirement appears to be satisfactory, but it should be remembered that the efficiency of even the most perfect treatment technology is no more than 90%.