Vízügyi Közlemények, 2003 (85. évfolyam)
3. füzet - Orlóci I.-Szesztay K.: A vízvagyon állapotának változása a XX. században
412 Orlóci I.-Szcsztay К. Hoekslra, A. Y: Virtual water trade between nations. Global Change Newsletter, No. 54, Stockholm, 2003. Mc Neill, J. R.: An environmental history of the twentieth-century world. Norton and Сотр., London, 2000. OMFR: A Duna távlati komplex hasznosítása. Országos Műszaki Fejlesztési Bizottság, Budapest, 19K4. Orlóci l.-Szesztay K.-Várkonyi L.: National infrastructures in the field of water resources. Contribution to the International Hydrological Programme, Budapest-Paris, 1985. Orlóci L-Szesztay K.: A vízgazdálkodás anatómiájának vázlata. Vízügyi Közlemények, LXXXV. évfolyam, 1. füzet, 2003. Szesztay K.: Éghajlatváltozás és a hazai öntözési vízigények. OTKA - 716. sz. megbízásra készült szakvélemény. Kézirat, VITUKI. 1992. Szlávik L.: Az árvízvédelmi biztonság elemzése, VITUKI Közlemények 76, Budapest, 2003. * ф Ф Changes of the state of water resources in the 20 , h Century by Dr. István ORLÓCI and Dr. Károly SZESZTA Y DSc.. Civil engineers "Flic 20th Century was a period of growth far surpassing all former limit forecasts and growth-rate expectations in the fields of population, economy and technology ( Table I). The objective of this study was to show with some data and examples the traces, which was left by this stormy century on the fresh water resources of the globe. Next, the state, size and structure of the water resources of Hungary are discussed, within this global image. Finally the crucial points of integrated water resources management, needed for meeting the expectations of sustainable development, are discussed, along with the central tasks of water management policies, giving the frame for the former. The natural factors of water resources are found in the frames of the water budgets of con tinents, in which the rapid cycles of surface-processes are coupled in a fortunate way, from the point of view of water management, with the slow cycles of the subsurface processes (Figure I.). A special feature of the social impact of the changes that have occurred is that the externalities and internal water-management relationships of economic activities, which were masked in earlier periods, became value and interest forming factors in an ever widening cycle and this latter makes the establishment of the information-technical and institutional bases of integrated water resources management a central task of the governments (Figure 2.). On the price of historical experiences with catastrophic epidemics sufficient knowledge and technologies were accumulated by the second half of the 20 t h Century in the developed industrial countries for the safe solution of the water supply and sewerage of the settlements. The global solution of this task, however, is still lacking (Table II.). The rapidly growing water demands of the 20 t h century, of homes, agriculture and industry, necessitated the control of surface runoff, in an ever growing way, in the form of constructing valley dams and river barrages. This enabled the doubling of the irrigated area by the second half of the century ( Table III.). The hydrological and technical bases of river management date back to the riverine civilisations of ancient times. In this field the 20 th Century provided significant step-forward mainly in the construction materials, structural dimensions and international co-operation (Tables IV and I 7). The rapid growth of plant nutrient loads of rivers resulted in the eutrophication of lakes and closed internal seas, making this one of the heaviest problems of the century. This is shown in the example of the Mediterranean Sea, discussing historical changes and institutional development matters (Table VI). The excessive exploitation of subsurface water resources by highly developed well-drilling and pumping technologies and at water intake rates that exceeded natural recharge rates by orders of magnitude resulted in the depletion of these resources. This is discussed in the example of the Ogalla
