You are here:
Catchment hydrological responses to forest harvest amount and spatial pattern
Citation:
Abdelnour, A., M. Stieglitz, F. Pan, AND R. B. MCKANE. Catchment hydrological responses to forest harvest amount and spatial pattern. WATER RESOURCES RESEARCH. American Geophysical Union, Washington, DC, 47:21 pages, (2011).
Impact/Purpose:
Forest harvest effects on streamflow dynamics have been well described experimentally, but a clear understanding of process-level hydrological controls can be difficult to ascertain from data alone.
Description:
Forest harvest effects on streamflow dynamics have been well described experimentally, but a clear understanding of process-level hydrological controls can be difficult to ascertain from data alone. We apply a new model, Visualizing Ecosystems for Land Management Assessments (VELMA), to elucidate how hillslope and catchment-scale processes control stream discharge in a small Pacific Northwest catchment in response to actual and simulated harvest intensities and spatial patterns. VELMA is a spatially distributed eco-hydrology model that links hydrological and biogeochemical processes within watersheds. The model simulates daily to century-scale changes in soil water infiltration and redistribution, evapo-transpiration, surface and subsurface runoff, carbon (C) and nitrogen (N) cycling in plants and soils, and the transport of dissolved forms of carbon and nitrogen from the terrestrial landscape to streams. The study site is watershed 10 of the H.J Andrews Experimental Forest. WS10 is a 10-hectare forested catchment in which the former 450 year-old stand of Douglas–fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) was clearcut in 1975. We used observed data for this Long Term Ecological Research site in combination with published chronosequence data from other Pacific Northwest forest ecosystems to calibrate VELMA for simulating pre- and post-harvest hydrological responses of WS10. Simulated and observed daily streamflow are in good agreement for both the pre-harvest (1969–1974) and post-harvest (1975-2008) periods (Nash-Sutcliffe Efficiency = 0.807 and 0.819, respectively). To more closely examine hydrological responses to harvest intensity and spatial pattern, we conducted a series of virtual clearcut scenarios in which harvest area and location were varied independently. Simulated results show an essentially linear increase in stream discharge with increasing harvest area. For all harvest scenarios, stream discharge increased initially after disturbance and returned to pre-clearcut levels within 10 to 50 years. Fall increases in streamflow were large in absolute terms, whereas summer increases were large in relative terms. Moreover, simulation results showed that changes in streamflow were strongly sensitive to harvest location relative to the stream channel.