A reservoir evaporation system for evaporating fluid from an open reservoir of effluent containing a contaminant includes a fluid evaporator, an air pump, and an air supply conduit functionally connecting the fluid evaporator with the air pump. The fluid evaporator includes a vessel adapted to be positioned in an operative position partially submerged on the top surface of the effluent in the reservoir with a lower chamber submerged in the effluent and an upper chamber extending above the top surface of the effluent. In operation, air from the air pump mixes with the effluent inside the fluid evaporator and subsequently is discharged through exhaust openings. A fluid discharge pipe can also simultaneously discharge aerated effluent back down into the reservoir. Fluid is thereby separated from the effluent in the lower chamber by evaporation in a controlled manner that minimizes spread of contaminants to surrounding environments by wind.