This research combines mass transport theory with stochastic methods to derive a stochastic, variable flow, surface water quality model for water quality policy analysis. Steady-state flow assumptions and a series of differential equations reduce the information and number of equations required to completely specify the model. The newly developed hydrology model is applied to river salinity in the Colorado Basin to evaluate the effectiveness of alternative salt load reduction strategies in water quality management. Model results are used to illustrate the influence of salt load reduction, stochastic river flows, and water conservation on river water quality. ¿ American Geophysical Union 1993