Estimating Additional Water Yield from Changes in Management

Home Browse Search

i ? Zfl 15 c U ?..i a? 10 >- .? a? a4 ? U 0 • • • • ? . • •? • • • • • ' ?? •• • • • • • . • • 0 10 20 30 40 Years Since Treatment Figure 3. Increase in flow from Fool Creek plotted over years after Harvest. Timber harvest on Fool Creek did not result in a significant increase in summer storm peaks, attesting to the assumption that in water limiting systems the late summer precipitation is used on-site with or without over story vegetation (Troendle 1987). Observations made on Fool Creek, as well as other plot studies, at the Fraser Experimental Forest led to the development of a series of sub alpine water balance models that began in the 1970's. The first of these models, MELTMOD, simulated accumulation and melt of snow. This was followed by the WATBAL model, which incorporated MELTMOD, but in addition simulated a water balance for forest vegetation (Leaf and Brink 1973). The next generation model was LUMOD (Leaf and Alexander 1975), a land use simulator that incorporated output from an even-aged growth and yield model (RMYLD) (Edminster 1978) in the WATBAL model to simulate water yield responses to clear cutting. These early models assumed that clear cutting had the greatest impact upon snow pack accumulation, because at the time it was believed that the measured increase.. of snow, present in openings following timber harvest, was the result of increased deposition during the snow fall event and redistribution of snow intercepted in the surrounding canopy, between events. This relationship was incorporated in the models as a"Rho" distribution function (see Troendle and Leaf 1980) in which snow retention in the opening (or accumulation) was a factor of opening size. Thus, the 6