Section 2.5
Regional Patterns in the Water Balance of Alberta's Wetlands
Isotope analysis was used to study the flow of water through open water wetlands across Alberta


- Regional patterns of water flow through wetlands were investigated across Alberta.
- Concentrations of naturally occurring isotopes of oxygen and hydrogen were measured in open water wetlands. These data, combined with information on climate and watershed area, were modelled to quantify and map water balance indicators, including precipitation, surface flow into and out of wetlands, groundwater inflow and outflow, and evaporation.
- Patterns of water flow into and out of wetlands were revealed across the natural regions of Alberta. Highlights show that 47% of wetlands likely have groundwater inflow, and that 2% of wetlands (located mainly in the mountains) appear to receive surface flow from snow and glacial melt outside the delineated watershed areas. In terms of outflow, 13% of wetlands (located mainly in the prairies) lose water mainly through evaporation, and 87% have surface and/or groundwater outflow.
- The results of this study provide baseline information about the basic hydrology of wetlands in Alberta, which can be compared with future measurements.
- Full study results are available in Gibson et al. 2022[1].
Background
Wetland hydrology is the study of the distribution and movement of water through wetland ecosystems.
- Wetland water balance is used to quantify the sources of water entering and leaving wetlands through measurements of the main components of the water cycle, including direct precipitation, surface flow into and out of the wetland, groundwater inflow and outflow, and evaporation.
- The flow of water through wetlands is affected by natural factors such as climate, underlying geology, landscape position, vegetation, as well as by human disturbances within and around the wetland.
- Understanding a wetland’s water balance is important to ensure an adequate and persistent supply of water, and to minimize the effects of development activities on a wetland’s natural functions, including flood mitigation and water storage, maintenance of water quality, and habitat supply for wildlife and plants.
- The purpose of this study was to examine regional patterns in the water balance of open water wetlands across Alberta using isotopes. Concentrations of naturally occurring isotopes of oxygen and hydrogen molecules were used to trace the movement of water in wetlands.
Components of the water cycle that are measured to quantify the water balance of open water wetland ecosystems (modified from Gibson et al. 2022).
More about isotopes


Water samples are collected from open water wetlands...

...and transported to the lab...

...where isotope concentrations are measured.
- Isotopes are varieties of a specific atom, such as hydrogen or oxygen, that have the same number of electrons and protons but a different number of neutrons. Isotopes therefore have different atomic masses, which can be used to trace water origin, movement, and residence time.
- Water molecules (H2O) are composed of two hydrogen atoms and one oxygen atom. A widely used technique for quantifying the hydrology of wetlands involves measuring the concentrations of naturally occurring isotopes of oxygen and hydrogen contained within water molecules.
- The isotopes examined in this study were oxygen-18 (18O), which has two more neutrons than “normal” oxygen, and deuterium (2H), which has one more neutron than “normal” hydrogen.
- Concentrations of these isotopes vary in response to natural processes. For example, when water evaporates from a wetland, more of the heavier isotopes (oxygen-18 and deuterium) are left behind, increasing their relative concentrations in the wetland and providing information about whether the outflow is dominated by evaporation compared to water outflow (surface and/or groundwater).
- In wetlands, heavy isotope signatures in surface water as well as isotope mass balance models can be used to determine the main source of water, either surface water or groundwater, for open water wetlands.
- For 87% of open water wetlands in Alberta, water loss is due to a combination of evaporation and surface and/or groundwater outflow.
- Evaporation is the main mechanism of water loss for 13% of assessed wetlands; these wetlands are scattered across the province, occurring as individual sites or as local clusters.
- Evaporative wetlands appear to be more common in the western part of the Grassland Natural Region and in the transition area between the Parkland and Boreal Forest natural regions.
- Some remote or difficult-to-access areas of the province have yet to be characterized and sampled.

Evaporation is the main mechanism of water loss in many prairie wetlands.