Water Quality in Puget Sound The Marine Water Condition Index (MWCI) displays changes in the water quality of Puget Sound. Numbers greater than zero show water quality that has improved over the baseline, and numbers smaller than zero indicate decreased water quality. Two areas in or near Thurston County are tracked as part of the MWCI: South Sound, a combination of the Nisqually Reach and Dana Passage measuring stations; and Budd Inlet. These stations have exhibited wide changes from year to year, but the overall trend is worsening marine water quality.
Water Quality in Freshwater Bodies Thurston County monitors water quality in specific bodies of water including water temperature, dissolved oxygen, pH, and fecal coliform bacteria. Thurston County began using a Water Quality Index (WQI) for the 2016-2017 water year. The WQI is designed to rate general water quality relative to expected water quality and uses a scale from 0 to 100. The higher the number, the better the water quality. Scores less than 40 suggest that water quality did not meet expectations and indicate such sites are of the highest concern for impairment.
Of the nine watersheds Thurston County tracks, the Totten Inlet watershed was of the least concern with a score of 85. Budd Inlet watershed had the lowest score (51).