A model of an irrigated, saline stream-aquifer system is constructed to simulate economic, agronomic, and hydrologic processes. The model is applied to a section of the Arkansas Valley in southeastern Colorado and is used to examine the effect of crop-mixing strategies on long-term profits. Mixing in excess of crop rotation requirements provides an index of farmers' willingness to exchange some profit for a reduction in the risk of short-term loss. The model contains three components. The economic component simulates water use decisions that maximize annual profit for each farm. The hydrologic component simulates salt transport by employing regression equations that predict changes in groundwater salinity as a function of hydrologic conditions and water use decisions. The agronomic component approximates changes in corn and alfalfa production in response to the depth and salinity of irrigation applications. Results from the entire economic-hydrologic-agronomic model are consistent with the few historical observations available for the site.