Project Themes and Components

Whole River Ecosystem Studies is currently the largest MAES theme consisting of 19 separate projects. The individual studies focus on the physical and biological structure and function of the river (11 projects) and the reservoir environments (six projects). The theme goal is to establish the physical and biological baselines for the study area, and develop a range of new metrics suitable for studying and monitoring large, multi-use rivers. 

Fish Passage is a theme initially focused on the diadromous species of concern/at risk at Mactaquac Dam and key issues already identified.  The goal is to inform the decision regarding the dam’s replacement or removal, e.g., the economic-ecological trade-offs (six projects ).

Environmental Flows is a theme designed to provide the preliminary information required to link flow directly to ecological structure and function in the Saint John River and including the associated floodplain connectivity.  The goal is to model and predict future flows and management regimes for securing the river ecosystem’s goods and services (four projects).

Project Theme


Project Name


1. Saint John River Ecosystem

1A.1 Defining the river environment



A topobathymetric (merged rendering of land elevation and water depth) LiDAR (LIght Detection And Ranging) survey will be conducted to provide the foundation for the project's bio-physical assessments and physical models.



Analysis of resolution, accuracy and information content of airborne laser ultra-shallow water surveys

This project will assess the accuracy, and minimum and maximum depth limits in the application of LiDAR as an effective tool in river management.



Spatio-temporal flow, temperature, and water quality baselines

An understanding of the spatial and temporal variations in river flow (from stage and velocities), temperature, and chemistry will underlay many of the project's models.

1A.2 River biomonitoring: baselines and metric development


Benthic macroinvertebrates

Baseline benthic macroinvertebrate community data will be collected to develop and apply appropriate metrics for the Saint John River.




Baseline fish community data will be collected to develop appropriate metrics for the Saint John River, e.g., diversity, abundance, and body condition.




Macrophytes (aquatic plants that grows in or near water and is either emergent, submergent, or floating) are important primary producers in rivers, providing habitat for benthic macroinvertebrates, and an important food source for waterfowl. This project will explore and document the macrophytes of the Saint John River.




Plankton communities downstream of dams are often dominated by reservoir species and these plankton can influence downstream food webs.



Trophic structure

The trophic structure (how organisms utilise food resources and therefore where energy transfer occurs within an ecosystem) of large rivers is highly complex yet essential to understand for effective decisions regarding multi-use rivers. Data collected from other biotic components of the project will be used to construct food webs within the comprehensive study reach.




The metabolism of the planktonic and benthic communities will be estimated using the light/dark bottle incubation and benthic chamber techniques which are less affected by varied water flow.



Decomposition and hypomycete characteristics

Metrics of decomposition rate will be calculated to understand the Saint John River. The structure and function of the hypomycete (fungi) community will be quantified to allow for an assessment of the fungal abundance, diversity, and biomass.



Modelling existing and future fish habitats - A quantitative approach

A mesohabitat approach will be applied to assess the spatio-temporal changes in habitat conditions downstream of the Mactaquac dam. This understanding will link directly to the modelling of the future river habitats using existing hydrodynamic modelling approaches.

1B.1 Reservoir environment


Water volume and sediment distribution - Reservoir bathymetric and sediment mapping

Bathymetry and sediment distributions are critical foundational data supporting the studies of possible dam removal. Bathymetry informs the estimated water volumes released and bank stabilities (erosion); sediments surveys are key to the transport and deposition modelling.



Accurate definition of sediment layering of the reservoir

One of the primary concerns with dam remediation is estimating the volume of sediment accreted since dam emplacement (45 years in the case of the Mactaquac dam).



Reservoir sediment composition, chemistry, and potential for downstream displacement

Baseline data on sediment composition and contaminants are needed in the models of downstream effects for a dam removal. Once sites of sediment deposition are identified, shallow sediment layers will be sample to examine the spatial variability and the magnitude of contaminant and nutrient concentrations.



Sediment re-suspension, movement, and fate post-dam removal

If the dam is removed, then sediment will be mobilized and transported downstream changing both the upstream and downstream fluvial geomorphology. A hydrodynamic model will be developed that includes the entire study area of the reservoir and river reach. Long- and short-term morphological changes and sediment distributions will be predicted to best understand how disturbed materials will move in the water column and their ultimate fate.



Final river setting following dam removal

A “new” river will form where the reservoir once existed in the dam removal scenario. This change to riverine habitats is not a simple return to the pre-dam river system because of the added sediments in and adjacent to the river channel, new erosion and aggradation sites, new debris dams, etc. Once channel placement and forms are predicted, we will use knowledge from the whole ecosystem study to predict (map) habitats and barriers for fishes in a new river.



Chemical and biotic source materials from the reservoir drawdown

In a dam removal scenario, ~350km3 of water must be displaced downstream. We will conduct a complete spatio-temporal analysis of the Mactaquac dam reservoir’s limnological conditions to understand the characteristics of water released in a dam removal scenario.

1B.2 Downstream water release


Flow and sediment transport modelling

To further inform the numerical modelling of a reservoir drawdown, a physical scale model of the Mactaquac dam and its turbines in a 2m x 10m flume will be designed, built, and tested. The model will accommodate flow through specific turbines as required, and tracers will be used to visualize the flow under various conditions.



Modelling predicted thermal regimes downstream during reservoir drawdown

The massive volumes of water to be released as the Mactaquac dam is removed have the potential to alter temperature regimes downstream; consequently, we need to predict temperatures under various release scenarios to minimize the temperature impacts. The model is based on physiography (topography and land use - hydrologic elementary representative areas) and a non-linear approach to vertical routing of water.

2. Fish passage



Fish passage for multiple species at large dams: A Workshop

We will begin our studies with a comprehensive literature review and synthesis of the current state of understanding of fish passage for multiple species and large dams. We will host an expert workshop to discuss global views on fish passage for multiple species. The outputs from the workshop and visits will be used to conceptualize engineering design options for fish passage at a future Mactaquac dam.



Reservoir transit and downstream approaches to a large dam by Atlantic salmon

Downstream movements of Atlantic salmon present challenges at two spatial scales. The capability of smolts (downstream) and adults (upstream and downstream) to negotiate the ~100km long reservoir is not understood. Pathways will be mapped and synthesized with the limnological data to best understand reservoir bottlenecks, dam approach and departure routes.



Restoration potential for reproduction by striped bass

As striped bass still migrate and are distributed during its spawning period throughout the Saint John River downstream of the Mactaquac dam, it is a candidate for population recovery using engineered reproductive habitats downstream of the Mactaquac dam.



Sturgeons and their habitats

Acoustic telemetry will be used to track Shortnose and Atlantic sturgeon to determine the location of spawning grounds of both species and to extend the understanding of seasonal habitats of adults in the Saint John River. Future spawning sites for flow regimes predicted for either the dam renewal or removal scenarios will be identified.



Near dam, spatio-temporal distribution of migrating American eel elvers

Since 1980 when the last two turbine units came online at the Mactaquac dam, eel elvers are no longer reported arriving at the Mactaquac dam fish trap, which suggests a velocity barrier for their migration. The distributions of elvers on their final approach to the Mactaquac dam will be explored to ascertain the success of passage upstream to this presumed barrier.



The ecology of muskellunge, an introduced predator, in the vicinity of a large dam

Muskellunge were introduced upstream of the Mactaquac dam and now occur up- and downstream of the dam, but spawning sites remain unknown. Their impact on the Saint John River ecosystem is similarly unknown. Habitat and spawning habitats will be located while quality of nursery habitat will be assessed by monitoring growth rate and abundance.

3. Environmental flows



Environmental Flows: A Workshop

A comprehensive literature review of the current state of understanding for large river and dam management will provide the foundation for an expert workshop to discuss global views on environmental flows and large dams, e.g., hydrological models, future climate change, and technological advances in turbine engineering and optimization. The outputs will inform the environmental flow modelling and advice to NB Power regarding effective environmental flow management into the future.



Climate and future hydrological regimes

Climate is changing and therefore future river discharge regimes are changing which presents serious economic and engineering challenges for both existing and future hydroelectric generation. Drawing on the outputs from using our multiple river models paired with downscaled climate information, the trends for the hydrological and thermal regimes will be predicted for the Saint John River for different climate scenarios.



Environmental and future flows with habitat implications for riparian insect species

The Saint John River watershed provides the critical habitat (sensu COSEWIC) necessary for the conservation of three insect species at risk within NB two dragonflies, Gomphus ventricosus (Skillet Clubtail) and Ophiogomphus howei (Pygmy Snaketail), and a riparian habitat specialist, Cicindela marginipennis (Cobblestone Tiger Beetle). The spatial distributions will be evaluated against the detailed riparian maps and the future flow scenarios to assess the potential loss of emergence habitats for these species.



Historical, current and future lateral connectivity within the floodplain

The Saint John River ecosystem boasts substantial wetland habitats sustained by the lateral connectivity with its largely intact floodplain. The historical, current, and future connectivity across the main channels and the wetland complex will be assessed  to quantify the change in connectivity among wetland habitats and the main channel. These results will help structure sampling of the current wetland biodiversity measured through DNA-based biodiversity analysis.