EXTRAPOLATION OF WATER-YIELD IMPROVEMENT STUDIES ON UPLAND WATERSHEDS TO LARGER RIVER BASINS

Extrapolation of the results from water-yield improvement studies to increase streamflow from on upland watersheds to larger river basins and then to downstream points of water use involves a series of sequential steps. Conditions on the upland watersheds from which results of the studies are extrapolated must be characterized in terms of the climatic, physiographic, vegetative, institutional, social, and economic conditions on the watersheds. Areas within the larger river basins that are not constrained by these conditions are then delineated relative to the possibility of implementing the results of the water-yield improvement studies. Increases in streamflow estimated from these treatable areas in the larger river basins are routed to downstream points of use in the temporal context of delivering the estimated increases in water supply to these points in the final step of the extrapolation process. While this extrapolation process has been followed in earlier analyses (Thorud 1974, Ffolliott and Thorud 1975), knowledge of the potentials for water-yield improvement is more comprehensive at this time (Baker 1999, Baker and Ffolliott 2000), and methodologies to implement the extrapolation process are more sophisticated. CONDITIONS ON WATERSHEDS Conditions of the upland watersheds studied must be summarized in terms of the climatic, physiographic, vegetative, and other relevant biophysical features and institutional and socioeconomic conditions to provide a basis for extrapolation of the results from these watersheds to the larger river basins. The watersheds are characterized by: Ownership status- responsible administrating agency on public lands