The primary goal of the Green Duwamish Water Quality Assessment (GDWQA) was to provide analytical tools to evaluate water quality issues in the Green-Duwamish River watershed from 2002 to 2003. Commercial/Industrial land use exhibited significant positive correlations with ammonia nitrogen, total zinc, and dissolved iron. High-density residential land use exhibited significant positive correlations with fecal coliform bacteria and dissolved zinc. Agriculture was most strongly correlated with orthophosphate, total phosphorus, and dissolved copper. Finally, effective impervious area showed significant positive correlations with E. Coli, ammonia nitrogen, total copper, total mercury, and total and dissolved zinc. Additional analyses included principal component analysis, correlations between water quality and hydrologic parameters, hysteresis analysis, storm versus baseflow loading comparison, and a comparison among the various sampling strategies employed.