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Client:
Clallam County |
Background
Prompted by Washington’s HB 2514 Watershed Planning Act,
regulators are considering ASR as a statewide approach for storing water
for peak summer supplies and instream flow enhancement. We evaluated the
usefulness of ASR in the western portion of Water Resource Inventory Area
(WRIA) 18, which includes Morse Creek and the Elwha River.
Challenges
Prior to our work, no detailed hydrogeologic evaluations had been conducted
in the study area. In addition, stakeholders expressed divergent needs
for ASR and additional water. For example, the City of Port Angeles enjoys
abundant inchoate water rights; however, using these rights would affect
instream flows in the Elwha River. The Lower Elwha Klallam Tribe is lobbying
for additional water to bring back the anadromous Elwha River salmon run.
Complicating matters is the imminent removal of the Elwha River dams.
Approach
We developed a conceptual hydrogeologic model using basic tools. Several
hydrostratigraphic cross-sections were drawn to understand the extent
of various aquifers and the degree of confining pressures they impose
on the groundwater system. We mapped regional flow directions to evaluate
the potential for groundwater to leak from the cross channels that incise
deeply into the glacial soils. Using Geographic Information Systems (GIS)
techniques, we mapped aquifer transmissivity based on information in our
database of over 500 well logs.
Outcome
Our analysis found some potential for storing and recovering small quantities
of drinking water—about 1 MGD. However, these quantities are unlikely
to be useful for augmenting instream flows in the Elwha River, which needs
at least 5 to 10 MGD to derive benefits. ASR may be effective for enhancing
flows in Morse Creek, the smaller of the two streams.