Research Feature
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Careful application of “Best Management Practices” in forest management can prevent impacts from harvesting on water quality
Key messages
Water Treatment Costs Reduced by
per cent
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Summary
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The broad objectives of this research were to evaluate the comparative impact of three alternative forest harvesting strategies on hydrology, water quality (including drinking water treatability), and aquatic ecology in Rocky Mountain headwaters of the Montane Cordillera and downstream into increasingly larger receiving rivers. Three sub-catchments of Star Creek in south-west Alberta were harvested using three harvesting
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strategies (clear-cutting with retention, strip-shelterwood, and partial cut harvesting) and watershed impacts were evaluated using a powerful, before-after: control-impact (BACI) study design using long-term coupled climatic, hydrologic, water quality, and aquatic health data from pre- (2004-2014) and post-disturbance (2016-2023) periods.
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The key findings were:
In this regard, our study design enabled the most powerful ability to detect such impacts, but these impacts were not evident across a broad range of downstream spatial scales. Indeed, while we expected watershed impacts would be associated with either differences in harvest intensity or road density among the three harvest strategies, watershed protection BMPs employed during harvesting effectively excluded evaluation of comparative impacts from the three harvesting strategies because water quality was either largely unaffected or actually improved after harvesting.
Practically, this research strongly supports the notion that careful application of BMPs to reduce erosion can not only limit adverse impacts from forest management activities, but actually prevent them from occurring. This outcome is critically important as it provides clear, scientific evidence showing there can be broader strategic alignment between provincial forest management and water management objectives than often perceived by forest and water management professionals and policy-makers highlighting the critical importance of careful application of BMPs for watershed protection.
- Forest harvesting increased snowpack water equivalent and resulted in earlier snowmelt in harvested areas which generally advanced the timing of streamflow and increased total annual water yield. However, these hydrologic effects in harvested headwaters sub-catchments did not produce detectable changes in hydrology downstream in larger receiving rivers.
- No impacts from harvesting on stream nutrients (phosphorus, nitrogen, dissolved organic carbon) or drinking water treatability parameters (UV254 or SUVA) were detected in headwaters catchments or further downstream in larger receiving rivers.
- The most notable water quality findings were that harvesting (including application of best management practices (BMPs) to limit erosion during harvest along with post-harvest reclamation) not only prevented impacts to stream sediment regimes, but actually improved sediment water quality (TSS and turbidity) after harvesting compared to stream sediment regimes over a 5-11-year period prior to harvesting.
- This is in stark contrast to very large and lasting impacts of wildfire disturbances on water quality we observed in two regional wildfires.
- Despite post-harvest improvement of sediment and nutrient water quality observed in headwaters catchments, none of these effects were detected in larger downstream receiving creeks/rivers.
- No harvesting effects on aquatic ecosystem health/productivity were detectable in either headwater’s streams, or further downstream.
In this regard, our study design enabled the most powerful ability to detect such impacts, but these impacts were not evident across a broad range of downstream spatial scales. Indeed, while we expected watershed impacts would be associated with either differences in harvest intensity or road density among the three harvest strategies, watershed protection BMPs employed during harvesting effectively excluded evaluation of comparative impacts from the three harvesting strategies because water quality was either largely unaffected or actually improved after harvesting.
Practically, this research strongly supports the notion that careful application of BMPs to reduce erosion can not only limit adverse impacts from forest management activities, but actually prevent them from occurring. This outcome is critically important as it provides clear, scientific evidence showing there can be broader strategic alignment between provincial forest management and water management objectives than often perceived by forest and water management professionals and policy-makers highlighting the critical importance of careful application of BMPs for watershed protection.
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Photo: Working onsite with partner X.
Contributors
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Partners:
Alberta Forestry and Parks Alberta Innovates Canfor Parks Canada Researchers: Uldis Silins, Miles Dyck, Sylvie Quideau (UofA), Mike Stone, Monica Emelko (UWaterloo), Adrian Collins (Rothamsted Research, UK), Bommanna Krishnappan (National Water Research Institute - emeritus) |
Graduate Students:
Dan Greenacre (MSc), Samantha Karpyshin (MSc), Melissa Howard (MSc), Michael Stewart (MASc), Amanda Martens (MSc), Derek Mueller (MSc), Sheena Spencer (PhD), Chris Williams (PhD), Nathan Storey (MSc), Rebecca Baldock (MSc) Staff: Chris Williams, Erin Cherlet, Kalli Herlein, Michael Pekrul, Anna Larney, Kathryn Purdon, Daniel White, Emma Hawksworth, Sydney Enns, Brook Hehr, Eamon Turner, Kaegan Finn, Ferf Brownoff, Lewis Rodgers, Tye Stoesz, Madelyn Lux, Steven Thompson |
