An Evaluation of Mitigation Measures to Reduce Impacts of Peat Harvesting on the Aquatic Habitat of the East Branch Portage River, New Brunswick, Canada

Abstract

Abstract:The evaluation of impacts of peat harvesting on riverine ecosystems is essential to the implementation of adequate mitigation measures. The objective of the present study was to determine the potential impacts of peat harvesting on the physical (e.g., flow, suspended sediment concentration (SSC), water temperature) and biological (fish abundance) parameters of the East Branch Portage River, New Brunswick. This study was initiated in 2005 and a before and after study design was used to assess impacts. When the operational activities were initiated (spring 2007), 19 ha of peatland (15% of the total area scheduled for harvesting) was drained. The exploited area was drained through a network of ditches which emptied into a sedimentation pond. Drained water subsequently flowed into a 250 m vegetated buffer zone and discharged into the East Branch Portage River. Drained water did not diffuse throughout the buffer zone as expected. Rather, water tended to concentrate in a natural depression (channel) in the buffer zone, thus connecting the outflow of the sedimentation pond directly to the river. Two main results deserve attention. First, elevated SSC events were recorded in the East Branch Portage River downstream of the confluence of the channel formed in the buffer zone and the river. Periods of elevated SSC could be attributed to poor maintenance of the sedimentation pond. However, elevated SSC events were also recorded after pond maintenance and were concurrent with the timing of ditching activities within the peatland. Secondly, fish abundance was lower in 2007 compared to 2006 (predevelopment period). However, potential impacts of peatland development on fish abundance should be interpreted with caution at this stage of the study.

Impacts and prognosis of natural resource development on aquatic biodiversity in Canada’s boreal zone

“…Wetlands in general can be prolific sources of aquatic biodiversity among all the biotic groups we use as bioindicators, but the literature on the impacts of boreal peat mining on aquatic biodiversity is limited and is mostly focused on semiaquatic or bog plants (Table 6). Only one study was found that assessed the effects of peat drainage on fish and it was inconclusive, although there was some indication of reduced abundance (Clement et al 2009). We found five studies that assessed the effects on amphibians and aquatic invertebrates, and all reported adverse effects to varying degrees (Table 6).…”

Impacts and prognosis of natural resource development on water and wetlands in Canada’s boreal zone

“…Peatland drainage ditches in New Brunswick (just outside the boreal zone in the hemiboreal subzone (sensu Brandt 2009)) delivered elevated concentrations of suspended sediments to downstream receiving waters, despite the use of sediment settling ponds in the peat mining area (Clément et al 2009). In a separate study, St-Hilaire et al (2006) also recorded elevated suspended sediment concentrations in downstream areas below sediment settling ponds of peat mining areas.…”

Comparison of modelling approaches to estimate trapping efficiency of sedimentation basins on peatlands used for peat extraction

“…Most producers harvest peat using industrial vacuums, which requires that the living vegetation be removed from peatland and that the site be drained to improve drying and allow harvest of the superficial peat layer. The drainage waters are known to carry suspended sediments, both mineral (mostly clays) and organic (peat fiber), coming from surface and ditch erosion (Kløve, 1998;St-Hilaire et al, 2006, Clément et al, 2009Marttila and Klǿve, 2010). In Canada, best management practices require the installation of sedimentation basins to reduce the impact of suspended sediments on the receiving waters.…”

“…Two strategies are usually deployed to monitor SSC: intensive grab sampling, often with the help of auto-sampler (Marttila and Klǿve, 2008) or deployment of turbidity sensor capable of high frequency monitoring (Samson-Dô and St-Hilaire, 2018;Clément et al, 2009;Es-Salhi et al, 2013;Haahti et al, 2016;Pavey et al, 2007;St-Hilaire et al, 2006).…”