Rt map units are tidally influenced streams and rivers.  On shorter run streams this distance is not map-able at a scale of 1:25,000, although it certainly exists.  The two large glacier-fed rivers, the Kenai and the Kasilof, have extensive zones influenced by salt water.  The tidal influence extends 12 miles up the Kenai River and about 6 miles up the Kasilof.  On the larger clearwater streams and rivers, such as Deep Creek and the Anchor River, the highest spring tides move about a mile, or a little less, upriver.  Tidal (estuarine) influence is defined as water with salinity greater than about 0.5 parts per thousand.  These salinity measurements have not been formally made or published for western Kenai estuaries; the mapping reflects local knowledge especially that of Robert Begich for southern peninsula streams, and Larry Marsh for northern streams, both biologists with the Alaska Department of Fish and Game.