Wetland surface and groundwater interactions monitoring program
Authors: Strakowski J , Renic T , Clark J 
Published: March 2017

Wetlands are important elements of the natural environment. More than 63 km2 of the Conservation Halton watershed is covered with wetlands, 94% of which lie above the Niagara Escarpment, an area which is headwaters to major Conservation Halton creeks.
Wetlands have various functions and properties and their understanding draws on multiple disciplines from terrestrial and aquatic ecology, chemistry, hydrology to engineering. From a hydrological point of view, wetlands can store water, lose water through evapotranspiration, recharge underlying
aquifers, or collect groundwater discharge and convey it to local streams and rivers. Based on local topographical settings, geology, groundwater levels, climatic conditions the wetland hydrological conditions may differ. To understand the wetland hydrological functions, its hydroperiod and vertical
hydraulic gradient need to be understood.
In the fall of 2012 Conservation Halton, in collaboration with the Regional Municipality of Halton, initiated a wetland monitoring project to address a lack of data identified during the development and calibration of an integrated surface and groundwater GSFLOW numerical model for drinking water
source protection water budget studies in the Halton-Hamilton Source Protection Region. Specifically, the wetland monitoring program was designed to enhance the understanding of surface and groundwater interactions, their timing and fluxes. Five wetlands within Conservation Halton watershed were
selected and instrumented. Wetlands 1 through 4 are located above the Niagara Escarpment and Wetland 5 is located below it. Wetland 1 is located in the Mountsberg Conservation Area, Wetland 2 just north of 5th Concession Road and west of Highway 6 in Hamilton, Wetland 3 in Crawford Lake Conservation
Area, Wetland 4 in Hilton Falls Conservation Area, and Wetland 5 on private lands in North Oakville west of Sixth Line. Wetland 1 is classified as a swamp, Wetlands 2 and 5 are marshes, and Wetlands 3 and 4 are vernal pools.
Each wetland was instrumented with two drive point piezometers completed at different depths in close proximity. The shallow piezometers are completed at a maximum depth of 0.1 metres and effectively measure the wetlands' hydroperiod. The deep drive point piezometers were completed at depths between
0.4 and 1.5 meters to monitor shallow groundwater levels underneath wetlands. Each drivepoint piezometer was instrumented with an electronic datalogger measuring absolute pressure and temperature and collecting data at 10 minute or 1 hour intervals. To obtain accurate water height above sensor, the
absolute pressure data were then corrected for barometric pressure changes using atmospheric pressure data.
The results show that the wetlands above the Niagara Escarpment are very dynamic and depending on the wetland type and local conditions, they behave differently during precipitation events. The instrumented wetland below the Escarpment is not as dynamic and mostly depends on surface water. In 2015
and 2016 three additional wetlands were added to the network in collaboration with Conservation Halton staff. Together with our neighboring conservation authorities, who have similar monitoring programs, having more instrumented wetlands will allow to develop relationships between wetland type,
hydrology and occupying species. Collected data are an invaluable dataset to replicate natural processes in numerical modeling and a critical tool in local decision making, wetland management and watershed planning.