Recovering oil from a subterranean formation is disclosed, comprising processing a source water to produce a processed water stream and a reject water stream; injecting a first fluid into an injection well toward a first downhole exhaust, wherein the first fluid comprises the processed water stream; and injecting a second fluid into the injection well toward a second downhole exhaust, wherein the second fluid comprises the reject water stream or a produced water stream, wherein the first fluid is separated from the second fluid within the injection well; and producing oil via a production well.