Watershed Management Plan - Mason County

Sub-basin Summaries
Appendix
A
Duckabush Sub-basin
The Duckabush sub-basin, located in southeastern Jefferson County, covers
an area of 81.6 square miles (52,256 acres). The vast majority (89%) of the
sub-basin is situated in the Olympic National Park and the Olympic
National Forest. The remaining 11% of the sub-basin consists of privately
owned forests, rural residential property, and parks. Land-use along the
eastern portion of the sub-basin (along the lower 1.5 miles of the
Duckabush River) is managed for timber harvest and rural residential and
commercial development (Golder Associates, 2003).
The Duckabush River, originating near Mt. Duckabush, is the largest stream
draining the sub-basin. The Duckabush River drains into a broad estuary at
Hood Canal, four miles south of Brinnon (Golder Associates, 2003)..
WATER QUANTITY
Total discharge of water from the Duckabush River sub-basin, including
both surface water (streamflow) and groundwater seepage to Hood Canal,
is an estimated 333,642 acre-feet per year (AF/yr) (Golder Associates,
2003). Of this total, an estimated 254 AF/yr are allocated as surface water
and groundwater, and 40 AF/yr are consumed via permit-exempt wells.
Table 5, below, summarizes the known information on water quantity in
the Duckabush sub-basin.
Table 5. Summary of Water Quantity in the Duckabush Sub-basin
Annual volume
(Acre-feet per year)
Estimated surface water discharge 330,891
Estimated groundwater seepage 2,751
Total estimated discharge 333,642
Surface water allocation 68
Groundwater allocation 186
Total allocation 254
Estimated permit-exempt well use 40
Of the 254 AF/yr of allocated water, approximately 67% is allocated for
domestic and municipal uses, with 32% allocated for irrigation. Less than
400 people live in the sub-basin (Census 2000), the majority of whom
(estimated at 306) draw their water from permit-exempt wells; total
estimated residential demand is 48 AF/yr. In 2010, an estimated 56 more
people will live in the sub-basin, increasing projected residential demand to
56 AF/yr (Golder Associates, 2003).
Final Plan for County Adoption – May 11, 2006 page 69