Forest Investment Account (FIA) - Forest Science Program
FIA Project M085276

    Peak flow and water yield responses to mountain pine beetle infested and salvage logged watersheds in the Kootenays
Project lead: Alila, Younes (University of British Columbia)
Contributing Authors: Bewley, D.M.; Alila, Younes; Teti, Patrick; Leech, Susan; Hafer, Mark
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Concerns for water quantity, water quality and fisheries resources have raised questions about the impact of MPB on annual water yield and peak flows. Answers to these questions are urgently needed as BC moves towards a large scale timber harvest salvaging strategy that is supposed to minimize economic losses while reducing environmental impacts (Snetsinger 2005). There exists a great deal of literature about the effects of healthy forest and conventional timber harvesting on streamflows from process stand level (e.g. Troendle and Reuss 1997, Winkler et al. 2005), empirical paired watershed (e.g. Stednick 1996, Troendle et al. 2001) and watershed scale modelling (e.g. Schnorbus and Alila 2004, Whitaker et al. 2002, Bowling et al. 2000, Waichler et al. 2005) studies. In the pine forest of BC, the winter snow accumulation and spring melt drive the hydrologic regime, which in turn is controlled by processes such as canopy interception, evaporation, tree transpiration, melt and groundwater storage. The effects of beetle-kill on these processes, with or without salvage harvesting, is largely unknown and may or may not mimic that of conventional timber harvesting (Uunilla et al. 2006). Since dead trees do not transpire, the effects of beetle-killed and newly harvested stands on transpiration processes may be the same; however the effects of beetle-kill on interception and melt processes may be different. After beetle attack, trees retain their needles for 2-4 yrs and retain branches and stay standing for many more years. Beetle-killed stands may retain live understorey vegetation and are not necessarily impacted by road developments, unlike conventional harvested stands. Only few paired watershed studies on the effect of insect infestation (Mitchell and Love 1973, Bethlahmy 1975, Potts 1984) and two others on the effect of salvage harvesting (Cheng 1989 and Moore and Scott 2005) on streamflow characteristics have been reported in the literature. However, the level of disturbance reported in these studies does not exceed 35% of the whole watershed and therefore are not large enough to be of relevance to the larger scale disturbance questions raised in this study. Only one infested forest stand level investigation had been reported in the literature from the Rocky Mountain of Colorado by Schmid et al. (1991). Their findings indicated that net precipitation under recently infested stands (few years after infestation before trees loosing their needles, so called brown attack) is not significantly different from its respective controls. The authors explained the possible reasons for these findings by the needle retentions of beetle-killed trees and the presence of a young and live understorey that has the potential for mitigating the effects of the beetle-kill. They also suggested that analogues between conventional partial cuts of healthy and beetle-killed forests may be valid, but only in even-aged stands (i.e. without significant understorey) and only after beetle-killed trees have begun to lose their needles. It is tempting to draw analogues, albeit in an opportunistic ways, between infested (defoliated) conifer stands and healthy (leafless) deciduous stands to take advantage of the wealth of knowledge in the literature on stand level processes in deciduous forest (e.g. Hardy et al. 1998). However, while the forest canopy architecture (tree elements and gaps) of the two forest stands may lead to similar interception and melt processes they would certainly be different in transpiration and its subsequent effects on soil moisture. Over the last two years, several projects have been initiated to quantify the differences in processes between a clearcut and infested brown and grey (i.e. after the infested stands lose their needles) forest stands (e.g. MPBI 8.26 on soil moisture & MPBI 8.39 on snow processes). The challenging question related to these types of studies is how this stand level knowledge translates to an operationally useful watershed scale functions such as streamflow? The effects of forest management on watershed scale functions had traditionally been investigated using paired watersheds. In recent years, however, the use of models to quantify the effects of forest management on hydrology has intensified, particularly at heavily instrumented watersheds (Whitaker et al. 2002, Whitaker et al. 2003, Beckers and Alila 2004, Thyer et al. 2004, Schnorbus and Alila 2004a, Bowling et al. 2000, Leung and Wigmosta 1999, Waichler et al. 2005). A numerical modeling approach doesn’t require the expensive long-term data collection exercise of a paired watershed study. It uses a shorter period of extensively monitored hydro-climate data to develop and calibrate watershed model applications and uses them in long-term simulations to quantify the effects of alternative forest disturbance scenarios (Ziemer et al. 1991, Schnorbus and Alila 2004b). We propose to combine watershed scale modeling at the heavily instrumented Cotton Creek watershed of the Kootenays with results from recent stand level studies of infested forests (e.g. MPBI 8.39 on snow processes) to address four research questions: 1. What would be the effects of leaving the trees to die on the water yield and peak flow regimes (watershed scale hydrologic function)? 2. What would be the effects of total clearcut salvage logging with no retention on the water yield and peak flow regime? 3. What would be the effects of salvage logging with retention in the case of an even-aged and a multi-storied uneven-aged infested forest? 4. How is the magnitude of the impact of MPB infestation and treatment strategies on water yield and peak flow, from questions 1 to 3, affected by physiographic characteristics of the watershed? Our research methods in this project build, and draw heavily, on the experience we have gained over the last decade in experimenting with and applying the distributed physically based hydrologic model called DHSVM of Wigmosta et al. (1994) in scenario analyses at the already well established and long standing experimental watersheds in the interior of BC (namely the Upper Penticton Watershed Experiment in the Okanagan (Thyer et al. 2004), Redfish and Cotton Creek Experimental Watersheds in the Kootenays (Whitaker et al. 2003 and 2002, Schnorbus and Alila 2004a and 2004b), and Carnation Creek Watershed (Beckers and Alila 2004).


Final Annual Report (2.3Mb)
Protecting Our Water (Innovation Magazine Article, Jan/Feb 2008) (0.1Mb)
Extension Note (0.1Mb)
Mountain Pine Beetle and Topographic Influences... (Abstract) (74Kb)

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Updated August 16, 2010 

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