A framework is presented for compiling available data for assessing statistical relationships between water quality and several factors of climate, physiography and land use. Seventeen water-quality characteristics studied represent annual mean concentrations or calculated annual yields of suspended sediment, dissolved solids and various chemical species of nitrogen and phosphorus. Usable multiple-linear regressions were developed relating water-quality characteristics to basin characteristics for 14 of the 17 water-quality characteristics with standard errors of estimate ranging from 17 to 75 percent. These models can be used to estimate water quality at specific stream sites or to simulate the generalized effect of land-use characteristics on water quality. For example, observed nitrate yields were up to 20 times greater than the simulated background yields. This increase is indicated to be the result of chemical fertilizers, animal wastes, and urbanization. It was concluded that this was a viable method of assessing the relationships between water quality and basin characteristics on a regional basis.