Preserving, augmenting, and creating cold‐water thermal refugia in rivers: concepts derived from research on the Miramichi River, New Brunswick (Canada)

Abstract

Summer water temperatures are rising in many river systems in North America, and this warming trend is projected to intensify in the coming decades. Cold-water fish may alleviate thermal stress in summer by aggregating in discrete cold-water plumes that provide thermal refuge from high ambient river temperatures. Reliance on cold-water thermal refugia is expected to increase in a warming climate, and many river reaches already lack suitable thermal refugia as a result of an absence of thermal diversity. A comprehensive fish management strategy could proactively address this imminent threat to cold-water fish populations across North America by preserving existing thermal refugia, augmenting thermal anomalies to improve performance as refugia, and creating new thermal refugia in uniformly warm river reaches. We provide practical recommendations on how these measures can be accomplished based on insight derived from recent research focused on the Miramichi River, New Brunswick. Opportunities include limiting land use change, construction aggregate extraction (e.g. sand and gravel pits), and groundwater pumping/consumption. Existing thermal anomalies can be enhanced by controlling advective thermal mixing between cold-water tributaries and the river mainstem flow, installing riparian shading, and adding temporary structures for protection from avian predators. New refugia can be created by temporarily pumping groundwater to discrete points within the river during periods of thermal stress. These concepts are discussed in the context of a comprehensive thermal refugia management strategy. Copyright

Influence of landscape and hydrological factors on stream–air temperature relationships at regional scale

“…The study of streams TS makes it possible to identify the most sensi- (Wawrzyniak, Piégay, & Poirel, 2012) and be preserved by limiting advective thermal mixing (Kurylyk et al, 2015) or activated by geomorphological restoration of streams (Eschbach et al, 2017;Loheide & Gorelick, 2006). On small and medium streams, it is necessary to preserve and/or favour the presence of riparian vegetation to moderate TS (Fabris, Malcolm, Buddendorf, & Soulsby, 2018).…”

“…Limiting water abstraction during lowflow periods may avoid a disconnection of groundwater/surface water exchanges and ensure environmental flows during the summer (Elmore, Null, & Mouzon, 2016). Some cooling strategies proposed to reconnect streams to floodplains and to facilitate greater lateral and hyporheic flow exchanges (Beechie et al, 2012;Daniel Caissie & Luce, 2017;Kurylyk et al, 2015) but need to be tested at a regional scale.…”

“…There is therefore a growing interest in understanding the spatio-temporal variability of river thermal regime given the likely effects of climate change (increase of both the Ta and the evapotranspiration, shift in river flow regimes and of groundwater inflows, etc. The goal is to develop opportunities for mitigation and adaptive management of river systems (Boisneau, Moatar, Bodin, & Boisneau, 2008;Hrachowitz, Soulsby, Imholt, Malcolm, & Tetzlaff, 2010;Jackson, Malcolm, & Hannah, 2015;Kurylyk, MacQuarrie, Linnansaari, Cunjak, & Curry, 2015). The goal is to develop opportunities for mitigation and adaptive management of river systems (Boisneau, Moatar, Bodin, & Boisneau, 2008;Hrachowitz, Soulsby, Imholt, Malcolm, & Tetzlaff, 2010;Jackson, Malcolm, & Hannah, 2015;Kurylyk, MacQuarrie, Linnansaari, Cunjak, & Curry, 2015).…”

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

“…Local, shallow flow paths can be more sensitive to climatic and seasonal changes in evaporation and precipitation (Fraser et al, 2001;Kurylyk et al, 2014b;Menberg et al, 2014;Reeve et al, 2006) and may not contribute to the thermal stability of aquatic systems to the same extent as deep (> 10 m) regional aquifers. This noted, during the thermal study periods, groundwater temperatures range from 10-11 • C in on-site wells below the peat.…”

Groundwater–surface water interactions in Canada

“…This groundwater influx provides thermal refugia and supplies nutrients for a variety of plant and animal species (e.g. Kurylyk et al 2015). Groundwater-wetland and groundwater-lake connections are expressions of similar processes where an aquifer provides water to a shallow surface-water reservoir, or vice versa (e.g.…”