Climate change may affect stream solute concentrations by three mechanisms: dilution associated with increased precipitation, evaporative concentration associated with increased temperature, and changes in solute inputs associated with changes in climate-driven weathering. We developed empirical models predicting base-flow water chemistry from watershed geology, soils, and climate for 1976 individual stream sites across the conterminous USA. We then predicted solute concentrations for 2065 and 2099 by applying down-scaled global climate model predictions to these models. The electrical conductivity model (EC measures total dissolved solids) predicted mean increases in EC of 21 µS/cm (32%) by 2065 and 42 µS/cm (57%) by 2099. However individual stream responses ranged from 50% decreases to 4x increases. The greatest decreases occurred in southern Rocky Mountain and Mid-West streams, whereas southern California and Sierra Nevada streams showed the greatest increases. Generally, streams in dry areas underlain by non-calcareous rocks were predicted to have the greatest increases in EC with climate change. Predicted changes in other solutes (e.g., SO 4 and Ca) were similar to EC, although the magnitude of SO4 change was greater.
Available at: http://works.bepress.com/charles_hawkins/37/