Water balance and exploitation of the hydropower potential of water courses; 1 : 1 000 000

The water-economic balance compares the discharge characteristics of water streams with the existing need of discharge (99 % of need is satisfied). The needed discharges are represented by the use of water in the economic sector and by what is called the minimum balance discharge, which must remain in the stream because of ecological reasons. The streams were classified into three categories: (1) Active streams - discharges larger than 110 % of the needed discharges. Increased use of water is possible. (2) Tense streams - the discharges are at the level of 90 -100 % of the required discharges. Regulative measures of water consumption are needed occasionally. (3) Passive streams - the discharges cover less than 90 % of the requirements on the discharges needed. Apart from the regulative measures in water supply, economising of water should be the issue of permanent concern in all consumer groups and the measures oriented to increased potential of water resources in dry spells should be implemented. Exploitation of water streams for production of energy is represented by the hydroelectric power stations of Slovakia. Three kinds of hydroelectric power stations are distinguished: hydroelectric power station, re-pumping hydroelectric power stations, and small hydroelectric power stations performing more than 0.5 MW. Hydroelectric power stations produce in average around 4,600 GWh of electric power, which is 20 % of the total electric power produced. (authors)