The river systems on the coast do not suffer urban, industrial, or agricultural runoff issues for the most part, except in parts of the Chehalis basin, which in its enormous extent is a microcosm of all western Washington watersheds rolled into one. Water quality trends have remained steady but below optimal primarily due to high summer temperatures and high sediment levels from erosion and increasing glacial disintegration in the Olympic Mountain watersheds.
Stream flows on the coast are characterized by extremes with peak flows during the winter caused by heavy rain and issues with aquafer and snowpack storage needed to offset low flows in the summer.
WATER QUALITY INDEX – CLICK >> TO OPEN LEGEND
WATER QUANTITY – CLICK >> TO OPEN LEGEND