Wetlands & Agricultural Water Management in Saskatchewan

What is a wetland?
A wetland is an area where water sits long enough to change the soil and plants. This is the standard definition of wetlands that has been established by the Canadian Wetland Classification System. This includes areas where water may only occur for a short portion of the year, e.g., a few days after the spring snowmelt. 

In Saskatchewan’s agricultural area, wetlands include lakes, creeks, rivers, and pothole wetlands. All of these types of wetlands are important for managing water in agricultural Saskatchewan. Pothole wetlands are the dominant wetland feature in Saskatchewan’s agricultural landscape. Water Security Agency uses a common classification system of potholes wetlands called the Stewart and Kantrud system to further describe these wetlands.

How many wetlands are there in agricultural Saskatchewan?
Over the last few years, Saskatchewan has made substantial progress mapping wetlands. We now have an inventory that covers 47 million acres of Saskatchewan’s agricultural lands. Access to this new data source provides an opportunity to generate more accurate estimates of wetland loss than have been previously available.

Within the inventory area, 4.7 million wetlands have been mapped representing 4.6 million wetland acres. This includes both drained and undrained wetlands.

Wetlands mapped include the full range of system types included in the Canadian Wetland Classification System (National Wetlands Working Group, 1997) including lacustrine (lake types), riverine (flowing water type) and palustrine (marsh, pothole type) wetlands.

How are wetlands mapped?
Wetlands are mapped using digital pairs of images that allow the wetlands to be seen in 3D. Differences in the colour and texture of the image can be used to see where soils and vegetation change from wetland to upland. To ensure accuracy of the mapping, WSA hires a consultant – separate from the original consultant who did the mapping- to go over the mapping and catch errors. Wetlands are captured regardless of the permanency of the water.

The wetland inventory maps drainage works, as well as intact and impacted wetlands. This includes every wetland feature that is 200 m2 and larger. During the mapping process, the area of each wetland, and its status (intact, partially drained, completely drained, partly filled, constructed, and farmed but not drained) are recorded.
Wetlands that have been drained are also mapped. This type of wetland can usually be detected by the changes in the colour of the image. To ensure that the status of the wetland is as current as possible, recent photos (e.g. 2007-2015) were typically used for the mapping.

Because drained wetlands can be mapped, the information can be used to represent all the wetlands that would have occurred historically before European settlement. If the wetland mapping is used this way, it’s important to understand how many drained wetlands were missed in the mapping process.

One way to do this is to compare the mapping to historic air photos before most wetlands were drained. WSA did this in one large area of the Quill Lakes watershed. On an area of one million acres in size, wetlands were mapped from 1960s air photos and compared to mapping that was done from 2017 imagery. The 2017 mapping did a better job of capturing wetlands than the 1960s photos. More work needs to be done to improve and validate wetland mapping but the evidence to date suggests that the wetland inventory could be used to represent the number of historic wetlands that have been drained.

How many wetlands have been drained in Saskatchewan?
The new larger data sets (i.e., WSA’s wetland inventory) indicate that only 14 per cent of pothole wetland area has been drained. This means that approximately 86 per cent of the pothole wetland area is retained – this excludes portions of partially drained and partially filled wetlands.

Previous estimates of wetland loss in Saskatchewan ranged from 40-70 per cent. These estimates were made using the best available data at the time but did not have access to the large data sets which are now available.

Many wetlands are cropped annually but are not drained.  These wetlands provide much of the flooding and water quality protection of intact wetlands but do not provide quality habitat.  Together, farmed and drained wetlands are about 28 per cent of the pothole wetland area. This means that if you remove farmed wetlands there is approximately 72 per cent pothole wetlands by area on the landscape.

These numbers are representative of the pothole wetlands which are the dominant feature on the landscape, meaning that if lake and river type wetlands were included the percentages remain nearly the same.

The value of 14 per cent above represents the cumulative pothole wetland loss in the entire wetland inventory area. It is noted that there are localized regions which have experienced higher levels of loss. Understanding localized levels of loss is important to understand localized impacts (e.g., flooding of roads). WSA examines wetland retention at a local scale when reviewing drainage works to address any localized impacts.

How do drainage and wetlands go together?
On the Saskatchewan landscape, landowners drain the wetlands they need to bring productive land into production but retain wetlands where it makes sense. Wetlands typically co-exist along with drainage. For example, in the Qu’Appelle Watershed, sections with drainage currently retain 78% of the wetlands. Farmers can manage the land to achieve the productivity and efficiency of modern farming while still practicing environmental stewardship. 

How much wetland area is made up by the different wetland permanence classes?
Pothole wetlands in Saskatchewan are often described by their permanence class:

Class V – Permanent wetland that almost never goes dry.
Class IV — Semi-Permanent wetlands that usually have water into the fall.
Class III — Seasonal wetlands that usually have water into the late spring or early summer.
Class II – Temporary wetlands that usually have water for a few weeks.
Class I – Ephemeral wetlands that that only have water for a few days in the spring.

To better understand how much of each wetland permanence class occurs in the landscape, WSA had classified over 6,000 wetlands in five sites distributed in contrasting landscapes across Saskatchewan’s pothole region. A subset of 1,787 wetlands were analyzed in 3D using LiDAR to determine volume of wetland storage.

In a typical pothole landscape, Class I/II/III wetlands is around 50 per cent of the wetland area and 35-40% of the water storage. At one site near the edge of the northern forest, Class IV and V wetlands comprised 76 per cent percent of the wetland area and 91 per cent of the wetland storage.

Continuing research
New techniques for wetland mapping are in development and WSA continues to invest in research to better understand wetland and drainage management. As better information becomes available, WSA will continue to use new information to improve water management.