Watershed Management Plan - Mason County

Sub-basin Summaries
Appendix
A
Appendix A.
Sub-basin Summaries
This appendix presents the “state of the sub-basin” – a summary of the
existing science – for each of WRIA 16’s six sub-basins. Information in
this appendix helped inform the “State of the Watershed” chapter (Chapter
2) as well as the key issues to be addressed for water quantity, water quality,
and habitat.
The sub-basins addressed in this chapter include:
• Dosewallips
• Duckabush
• Hamma Hamma
• Finch/Lilliwaup
• Skokomish (including the North Fork, South Fork, and mainstem);
and
• South Shore.
Dosewallips Sub-basin
The Dosewallips sub-basin is the northernmost sub-basin in WRIA 16 and
is the largest watershed entering the northern portion of Hood Canal. The
sub-basin drains an area of 130 square miles (83,825 acres), including nearly
132 miles of streams and tributaries. The Dosewallips River is one of the
largest rivers in eastern Jefferson County. The river flows east from the
snowfields of the Olympic Mountains into the Hood Canal near the town
of Brinnon. Additional creeks and tributaries in the sub-basin include
Rocky Brook Creek, Walker Creek, and Turner Creek (Golder Associates,
2003).
The vast majority (93%) of the watershed is contained within the Olympic
National Park and Olympic National Forest. The remaining land in the
watershed is rural residential, commercial, and private forest land. Brinnon,
the largest town in the sub-basin, is located at the mouth of the Dosewallips
River (Golder Associates, 2003).
WATER QUANTITY
The Dosewallips is the second largest river in WRIA 16 after the
Skokomish River. Total discharge of water from the sub-basin, including
both surface water (streamflow) and groundwater seepage to Hood Canal,
is an estimated 454,612 acre-feet per year (AF/yr) (Golder Associates,
Final Plan for County Adoption – May 11, 2006 page 65