March was National Engineering Month, which recognizes the field of engineering, including its many sub disciplines. The Canadian Rivers Institute (CRI) profiles one of the many examples of research within the institute that fuses the knowledge and expertise of ecological conditions and hydrologic processes in its mandate to develop the aquatic science needed to understand, protect, and sustain water resources.
Dr. Kerry MacQuarrie, a CRI Science Director based in the Department of Civil Engineering at the University of New Brunswick is one of the researchers that bring a hydrologic engineering perspective to the CRI network.
“An engineering approach helps to bring aspects of physical hydrology – the ‘bedrock’ so to speak – of our river systems to research on river conditions and processes”, says Dr. Kerry MacQuarrie. MacQuarrie feels that his involvement in river science is necessary and valued: “my colleagues are very appreciative of the engineering perspectives I contribute as most have a multi-disciplinary understanding of river dynamics”.
One of MacQuarrie’s areas of research focus has been to use water temperature profiling and modeling to understand groundwater and surface water interactions, including how groundwater temperature may be influenced by climate change. “Because groundwater temperature is often more constant and cooler [than surface water], we can look for the cooler areas within a river, stream, or estuary as an indicator of groundwater inflow”, explains MacQuarrie.
MacQuarrie has been a key member of a multi-disciplinary team working to identify and characterize the existence and temperature of thermal refugia in the Little Southwest Miramichi, a prominent salmon-producing tributary of the Miramichi River in New Brunswick. Thermal refugia are described as cold water plumes, often sourced by groundwater inputs into a river that become areas of refuge for fish when river temperatures rise and exceed critical species-specific temperature thresholds.
The Miramichi River watershed has seen increasingly stressful water temperature conditions for salmonids in summer months, mainly due to regional climate change. In previous fishing seasons, the federal Department of Fisheries and Oceans has closed pools to angling over concerns of stressed fish.
Led by three CRI Science Directors and three Associates, research on thermal refugia in the Miramichi is considered by MacQuarrie as “one of the best examples of CRI multidisciplinary research collaboration”. MacQuarrie continues, “I probably wouldn’t have had the opportunity to contribute to the research if not for the drive of my CRI colleagues and their passion for Atlantic salmon. I am an avid salmon angler, so that also helps me work with the fisheries biologists on the CRI team”.
The years of research culminated in a set of recommendations for managing thermal refugia that include: identifying the existing refugia, limiting watershed activities that may induce their warming, restoration of inadequate, expansion of existing and creation of new thermal refugia. While these recommendations are proposed for the management of the Miramichi River, they are also relevant to many other unregulated, alluvial channel rivers that are currently experiencing summer water temperature maxima that approach or exceed critical temperature thresholds for cold water fish.
“It has been ‘cool’ research”, MacQuarrie laughs “and I know that it would not have happened without the collaborative effort across our engineering and biological disciplines among the CRI network”.
More on the research
The work to develop recommendations for preserving, augmenting and creating cold water thermal refugia in rivers was derived from over ten years of research on the Miramichi river by a number of University of New Brunswick researchers within the CRI network.
Dr. Allen Curry (a CRI Science Director), Dr. Wendy Monk (CRI Associate) and Dr. MacQuarrie had previously mapped river temperature anomalies using aerial infrared technologies. Dr. Rick Cunjak (a CRI Science Director) and Dr. Tommi Linnansaari (CRI Associate) worked to determine if salmon were actually using these cooler areas for refuge during elevated river temperatures. Dr. MacQuarrie and former PhD candidate, Barret Kurylyk, brought in the engineering. They simulated temperature changes using field parameters to build a model of the groundwater influence, capturing details of thermal refugia. MacQuarrie and Kurylyk also ran New Brunswick climate change projections through the model to show how groundwater discharge rates and temperatures were changing under different climate scenarios.
MacQuarrie and Kurylyk found that a number of variables determined the temperature of the discharging groundwater, including depth to groundwater source, the groundwater recharge rate, and the thickness of the groundwater aquifer. Through changing the climate parameters of the model, they also found that groundwater may warm up more than most researchers had assumed.
The research shows that if the thermal refugia are fed from shallow aquifers, which have warming influence from the aboveground conditions, they may warm up within 5 to 10 years. Combined with more rapidly warming river waters, these refugia may also become less suitable for fish habitat during stressful thermal conditions. Therefore, thermal refugia preservation, augmentation and creation become increasingly important for the survival of Atlantic salmon populations.
This research has recently been published: Kurylyk, B.L., K.T.B. MacQuarrie, T. Linnansaari, R.A. Cunjak, and R.A. Curry, 2015, Preserving, augmenting, and creating cold-water thermal refugia in rivers: Concepts derived from research on the Miramichi River, New Brunswick (Canada), Ecohydrology, 8, 1095-1108, doi: 10.1002/eco.1566.