Abstract: A shrouded turbine for enhancing the levels of dissolved gas such as oxygen in water flowing therethrough. The turbine comprises a rotatably mounted runner within a stationary casing. The casing includes a head cover, a discharge ring and a draft tube which together define a water passage extending from an upstream inlet port to a downstream outlet port. A gas chamber substantially surrounds a peripheral portion of the draft tube, and a gas discharge slot connects the gas chamber to the water passage. The slot is substantially continuous and extends substantially about an entire circumference of the water passage. An oxygen containing gas source is connected to the gas chamber, and the gas pressure in the gas chamber is greater than a water pressure in the water passage adjacent the slot. Gas is discharged from the slot into the water passage so that the level of dissolved oxygen in the water discharged from the downstream port is increased.