The Henderson Inlet watershed lies in the northeast section of WRIA 13 and has a total drainage area of about 29,275 acres (Thurston County 1989). The topography of the watershed is divided into three parts: the Dickerson Point peninsula, the Johnson Point peninsula, and the Woodland Creek Basin. The three areas drain surface water into Henderson Inlet. Most of the basin lies at an elevation of less than 200 feet above sea level. The inlet is about five miles long from Dickerson Point to the mouth of Woodland Creek, ranging from .25 to .75 miles wide, and covering 2.5 square miles in area. It has an average depth of 25 feet, and reaches its maximum depth of 60 feet near the mouth (Thurston County et al. 1995). The southern head of the inlet forms an estuary at the mouth of Woodland Creek and reveals large mudflats at low tide.

The Henderson Inlet watershed includes rural, unincorporated areas as well as the heart of the city of Lacey and portions of the city of Olympia. As of 1988, the population and dwelling units within the watershed numbered 38,066 and 15,015 respectively. Between 1979 and 1989, over 41% of the new housing in Thurston County was built in the Henderson Inlet watershed. Growth by the year 2010 is projected to total 61,018 people and 24,847 dwelling units (Thurston County 1989).

Description from the Salmon Habitat Limiting Factors Final Report Water Resource Inventory Area 13. For more information including salmonid stock status see the previously stated document or the Salmon Habitat Protection and Restoration Plan for Water Resource Inventory Area 13, Deschutes.