Mactaquac Generating Station, a 672 MW run-of-the-river hydroelectric facility, was constructed in 1968 on the main stem of the Saint John River (SJR), New Brunswick, Canada and is owned and operated by NB Power. The facility is expected to reach the end of its service life by 2030, when the powerhouse and spillway will no longer be viable because of an alkali-aggregate reaction with the concrete. NB Power needs decide on a preferred option for the future of Mactaquac Generating Station by 2016. Options identified for the future include repowering the station with a new powerhouse and spillway, rebuilding the spillway only, or removing all parts of the station. The decision will be based on a combination of economic, environmental, and social consequences ( 

To make an informed, science-based decision for a preferred option, NB Power has engaged the Canadian Rivers Institute to design a large multidisciplinary aquatic ecosystem study to support their decision making process and subsequent regulatory requirements.


The Mactaquac Aquatic Ecosystem Study (MAES) is a planned, whole-river ecosystem study and manipulation. It begins with a multi-year assessment of the structure and function of a large river ecosystem, followed by a manipulation of flow, sediment load, and thermal regime with consequential effects on the ecosystem, and then a multi-year period to monitor the recovery to a new river state.

The manipulation will induce either an acute, major perturbation with long-term effects, i.e., removing the station and restoring the river to a free-flowing form, or a minor, lesser stress event created by the multi-year, re-construction of the station, but chronic in that the generating station and hydroelectric-related issues persist. A comprehensive study and planned manipulation of an ecosystem of this scale is one of the largest freshwater experiments attempted worldwide.

MAES takes a phased approach to address the scientific challenges for the future of the Mactaquac station. Phase I (2014 - 18) is the assessment of the key baseline environmental conditions and description of the environmental challenges and opportunities for either replacing or removing the station. Currently, 29 separate project components are planned, which are collectively described within three separate study themes.


View MAES reports here
August 29, 2016: 
MAES interactive Story Map is released 
May 9, 2016:  Canadian Rivers Institute student researchers hit the water to answer questions about river health 
May 5, 2016:  The Canadian Rivers Institute and NB Power’s Mactaquac Project
May 1, 2016: Check out CRI's online data and GIS depository live at
December 19, 2015:  Check out the MAES Summer 2015 team in action!
November 4, 2015:  The MAES Sediment Team and their beloved cores from the Mactaquac Headpond

This project could not take place without the valued financial contribution from the following organizations:

MAES funding partners

Important partners on this project include:

Notice to boaters of research activities on the headpond

The general public will  notice several buoys deployed across the headpond in the summer of 2016. These are a part of the MAES project and will help us learn more about the movements of fish community of the Saint John River. Below is a map of approximate locations. The buoys are safe to approach; a near-vertical rope connects a bottom anchor to a surface buoy. The public is advised to not use the buoys for mooring, and to not remove or attempt to move them as it is instrumental to the current studies to have the acoustic receivers (attached to the buoy set-up) in these locations. Explore the interactive map.



Photo credit: Énergie NB Power

At the funding announcement in October 2013.  Left to right: Craig Leonard (NB Minister Energy and Mines), Gaëtan Thomas (President and CEO Énergie NB Power), Dr. Allen Curry (Principal Investigator MAES, UNB and CRI), and Dr. Eddy Campbell (President UNB).