This chapter investigates the reservoir water in protected areas. These areas were selected so that the impact of human activity on water quality in the drought period 1982-1994 could be minimized. The effects of drought on surface water quality depend very much on local environmental conditions as well as on legislative and economic pressures, such as water quality targets for individual rivers and the price of licenses for effluent discharges. The drop in industrial and agricultural production in 1982-1994 on the whole produced some improvement in the quality of surface and ground water during the periods of drought. The deterioration of drinking water quality from surface waters during periods of drought may be avoided by using a variety of strategies. The historical use of mechanical and biological methods of waste water treatment has not sufficiently reduced problems of heavy metals, nitrogen, and phosphorus in Bulgaria.