Preliminary water-quality characterization of lakes in Washington

This report describes a method for comparing and characterizing lakes in Washington on the basis of water quality. The method can aid in selecting lakes for lake-restoration efforts. To simplify comparisons, a characteristic value (CV) was developed for each of 617 lakes in Washington using principal-component analysis. Three of 14 water-quality properties measured were used in this analysis because the principal component of the three properties accounted for 63 percent of the variance in the correlation matrix. The three properties were Secchi-disc visibility and concentrations of phosphorus and organic nitrogen. The significance of the derived CV's was evaluated by regression of chlorophyll a concentration against CV. The resulting standard error of estimate of +1.8 micrograms per liter of chlorophyll a indicated that the CV can be a useful index in assessing relative water-quality and trophic conditions among lakes.