Resilience of Lake Hydrodynamics and Wetland Biodiversity

There is a growing interest for fishing and game activities among the Canadian population and recreational tourism has increased significantly in the past decades.

Land conservation practices that make it possible for these activities to take place and ensure the presence of pristine locations for future generations is also on the rise. However, despite some studies on the subject, there is still only a limited understanding of integrated lake and ecosystem dynamics and how it can be impacted by human activities and climate change. Among the different components of a lake, groundwater inflow and outflow are probably the least well understood.

The goal of this project is to understand the resilience of lake/wetlands hydrodynamics with a specific focus on Lake Papineau in the Outaouais region. This lake is unique since it has been kept relatively pristine over the years as it was the core of a privately owned fish and game nature reserve. Recently, Kenauk Nature and Nature Conservancy of Canada have started a partnership to expand the area under conservation, to ensure its accessibilty to the public and to manage sustainable activities within the reserve.

This particular situation makes Lake Papineau a good reference point for comparative studies and for monitoring cumulative impacts, including ones associated with climate change. In order to properly manage the site, clear benchmarks will be identified based on state-of-the-art scientific knowledge concerning the lake dynamics and associated wetlands.

Photo credit: Gino Doucette.

• Quantifying lake hydrodynamics and estimating the long-term effects of land use and climate changes;

• Assessing the drivers and stressors controlling the richness and composition of plant and animal communities in wetlands;

• Formulating recommendations to land managers in order to prevent negative impacts of these stressors to and ensure long-term conservation of the Lake Papineau ecosystem.

• Establishing the lake water budget and its long-term hydrological resilience for current and past hydrological conditions;

• Characterizing wetlands and how they are affected by hydrological, climatic and land use stressors such as dams, recreational boating and shoreline deforestation;

• Define how land use change, climate change and human-induced pressures can impact the lake hydrology and the wetlands located on its shores and identify sites that should be part of a conservation network aimed at preserving biodiversity and ecological services.

The lake’s water balance for the period between October 2016 and September 2021 shows that the lake receives an average of 6% of its water supply from the aquifer, 18% from direct precipitation, and 76% from surface or hypodermic runoff. Outflows from the lake take place through the aquifer (2%), by evapotranspiration (10%), and by the lake outlet (86%). Lake levels can vary by up to 1 m during a hydrological year. The recharge and groundwater flow models used with 12 climate scenarios provided by Ouranos show a significant increase in precipitation, runoff and evapotranspiration (Fig. 1). Annual recharge does not vary significantly for future time horizons, but it could increase in winter (milder temperatures) and decrease in summer (increased evapotranspiration). High levels in the spring and extreme low levels may be more common in the future. However, this increase in inter- and intra-annual variability could have an impact on the lake’s water balance, on the flooding of the shores after snow melt, and on the drying of certain normally submerged areas in the dry season.

Figure 1. Changes in precipitation, runoff, evapotranspiration (EAT), and annual aquifer recharge based on the use of 12 climate scenarios.

Four types of wetlands were identified around Lake Papineau: ombrotrophic peat bogs (12), ash marshes (18), alder marshes (8), and emergent marshes (2). Wetlands of interest for conservation in the area were identified using an index of ecological uniqueness and biodiversity, highlighting a necessary compromise at the time of conservation. The main variables explaining the flora of the wetlands are the slope of the bank and the elevation of the site compared to the level of the lake. A limited decrease in lake levels could lead to the transformation of an alder marsh into an ash marsh and a loss of 0.6% of the wetland area. A significant rise in the level could lead to a gain in wetlands, while a significant decrease could cause the disappearance of 20% of the wetlands. It was also shown (Fig. 2) that peat bogs have ecosystem functions and services (EFS) for controlling bank erosion, regulating water levels, storing carbon and improving the aesthetic quality of the area. Ash marshes also have EFS for carbon storage and shoreline erosion, while alder marshes have EFS for fishing and aesthetics. Peat bogs contribute to the diversity of singing birds and insects, ash marshes contribute to the diversity of plants, and alder marshes contribute to the diversity of fish. The greater inter- and intra-annual variability in lake levels expected in the coming decades could have impacts on wetland ecosystem functions and services. 

Figure 2. Map of the intensity of the contribution in ecological functions and services of riparian wetlands to Lake Papineau.

• Institut de recherche en biologie végétale

• Kenauk Nature

• Nature Conservancy of Canada (NCC)

• Université de Montréal

• Université du Québec à Trois-Rivières