This report was prepared in support of the Ohio River Basin Energy Study (ORBES), a multidisciplinary policy research program supported by the Environmental Protection Agency. Water consumption levels associated with power plant cooling were estimated for different energy development scenarios for the Ohio River Basin; potential impacts of power plant consumption and pollutant emissions on ambient water quality were also estimated. Cumulative water consumption was compared to the 7-day 10-year low flow values for various locations along the tributaries and main stem of the Ohio River. The total potential consumption associated with projected municipal and non-power industrial use was also evaluated. Potential water quality impacts were estimated by assuming that constituents were conservative and were concentrated as a result of consumptive losses; this simplified approach led to useful insights. The projected cumulative effects of power plant cooling generally appear minor (e.g., less than 10% of low flows), although in some cases the effects would be much greater. For example, Scenario 1 specifies dispersed plant locations to ameliorate air pollution impacts, but more plants are located on the smaller tributaries and the potential water quality impacts would be greater than under other scenarios. In general, potential impacts on water quality would result mainly from plant consumption; thus, such impacts would generally be small in comparison to background levels although exceptions are noted.