By Sarah Boon, Rita Winkler, John Pomeroy, and Dave Spittlehouse
Abstract: One of the most important ecosystem services from forested regions is the provision of a sustainable water supply. In the United States, for example, streamflow from forest land provides almost 2/3 of the total freshwater supply (Jones et al. 2009). On a global scale, forested headwaters that are snowmelt-dominated produce 60% of total runoff (Chang 2003). Given that forest ecosystems are significantly affected by climate change and associated forest disturbance such as wildfire, insect infestation, and disease (Westerling et al. 2006; Littell et al. 2009), there is a critical need to quantify the subsequent effect of these changes on water supply.
In British Columbia, the Forest and Range Practices Act (FRPA) requires the forest industry to incorporate non-timber values such as water into their forest management plans using best available knowledge. The response of snow processes to clearcut harvesting is well understood, and has been used as a forest management strategy to increase water yield from headwater basins (Hibbert 1967; Bethlalmy 1974; Ziemer et al. 1991; Wigmosta and Burges 2001). However, we know little about the effects of natural disturbance, such as mountain pine beetle (Dendroctonus ponderosae; MPB) and wildfire, and much of this more recent knowledge is at the stand rather than watershed scale (Winkler and Boon 2009; Bewley et al. 2010; Pugh and Small 2011; Schnorbus 2011). Our research expands previous stand-scale hydrologic process research to the source area watershed scale. The results provide forest and water resource professionals with key information required to assess the hydrologic consequences of forest response to climate change, and to make scientifically defensible water and timber management decisions.