reservoir(An artificial or natural storage place for water, such as a lake or pond, from which the water may be withdrawn as for irrigation, municipal water supply, or flood control)
residential area with traffic calmings(Residential zones where raised areas are built across roads so that vehicles are forced to move more slowly along it)
residual amount of water(Amount of water left in a water course after it has fed a hydropower plant in order to maintain a satisfactory dry-weather-flow for allowing the survival of biotic communities)