Gaining Stream (effluent stream) - Stream or portion of a stream where flow increases because of drainage from groundwater.
A stream in which groundwater discharges contribute significantly to the streamflow volume. The same stream could be both a gaining stream and a losing stream, depending on the conditions.
Stream reach in which the water table adjacent to the stream is higher than the water surface in the stream, causing ground water to seep into the stream, increasing its flow. Also known as effluent stream.