ABSTRACT
About 97% of earth’s water is salt water in oceans and seas. Nearly 70% of the world’s fresh water is frozen in the Antarctic and Greenland ice sheets, glaciers, and permanent snow cover and ice. About 30% of all fresh water is groundwater. Lakes and rivers contain only about 0.25% of all fresh water. All over the globe, water is being diverted for industrial, agricultural, and household uses, and many lakes are suffering from the resulting lack of inflow. In 2002, the United Nations Environment Program (UNEP) announced that about three billion people would face severe water shortages by 2025, if the present consumption rates persist. Shallowing, desiccation, and degradation of certain freshwater and salt lakes and inland seas are among the major environmental problems at the beginning of the 21st century. There are clear indications that the growth of human population and the increasing use of natural resources, especially water, combined with climate changes, exert a considerable stress on closed or semienclosed seas and lakes. In many regions of the world, marine and lacustrine hydrosystems are or have been the objects of severe or fatal alterations ranging from changes in regional hydrological regimes and/or modifications of the quantity or quality of water resources, deterioration of geochemical balances (increased salinity, oxygen depletion, etc.), mutations of ecosystems (eutrophication, decrease in biological diversity, etc.) to the socioeconomic perturbations, which have been the consequences or may soon be in the near future.
