Profile of the SEAWA Watershed

*Alphanumeric codes correspond to Water Survey of Canada identifiers

The SEAWA watershed includes the South Saskatchewan River Sub-Basin within Alberta, and the closed-drainage system Pakowki Lake watershed (Seawa Watershed Map). Their areas are 14,765 and 5,164 km2, respectively, with a total area of 19,929 km2.  The South Saskatchewan River within Alberta begins at the confluence of the Bow and the Oldman Rivers and continues to the border with the province of Saskatchewan. The total population of the SEAWA watershed is around 70,000 people mostly concentrated in the urban centres of the City of Medicine Hat and the Town of Redcliff. Land use is predominantly agriculture. The SEAWA watershed belongs to the semi-arid grassland natural region of Alberta, and the South Saskatchewan Region under the Land Use Framework.

Large drainage basins are typically divided into smaller units, either “sub-basins” or “sub-watersheds,” to make them easier to manage.

The Government of Alberta defines the larger basin formed by the Bow, Oldman, Red Deer and the Alberta portion of the South Saskatchewan Rivers as the South Saskatchewan River Basin (SSRB). As part of the SSRB, the Alberta portion of the South Saskatchewan River is considered a sub-basin: a smaller, regional drainage area that contributes to the broader basin.

Located in the steppe region known as Palliser’s Triangle, it has a semi-arid, continental climate (Köppen climate classification BSk), with cold, dry winters and warm to hot summers. However, the winter cold is occasionally ameliorated by mild and dry chinook winds blowing from the west, and hot summer daytime temperatures are made more tolerable by low humidity and rapid cooling in the evening hours. The region receives less precipitation annually than many other locations on the Canadian Prairies and plentiful sunshine (Medicine Hat is widely known as “The sunniest city in Canada”). Maximum precipitation typically occurs in the late spring and early summer.

Also present in the region are the Cypress Hills, Canada’s first interprovincial park, and the highest point in Canada between the Rocky Mountains and Labrador (maximum elevation – 1,466 metres above sea level). The Cypress Hills are unique in that they were not glaciated during the last ice age; the park’s montane environment is an oasis of mixed lodgepole pine forests in the midst of the Canadian prairies.

Those who live in the SEAWA watershed typically consider their corner of south-east Alberta (the area that drains towards the South Saskatchewan River) as the South Saskatchewan River Basin. The SEAWA watershed Basin has been further divided into six sub-watersheds based on the unique drainage patterns and characteristics of the regional landscape.    

*Alphanumeric codes correspond to Water Survey of Canada identifiers

Description and Topography – South Saskatchewan River Sub-basin (SSRSB)

The SEAWA watershed, also known as the South Saskatchewan River Sub-basin (SSRSB), is located in the south east region of Alberta, roughly centered around Medicine Hat area.

Agricultural land use accounts for 80% of the SSRSB’s total land. About 25% of agricultural land is used for crops, while the majority, 63%, is used for pasture. Thousands of oil and gas wells are operated within the region, with the majority of gas processing plants located near Empress.

CFB Suffield, covering some 2,700 square kilometers offers one of the largest live-fire training areas in North America for military use. The Base has set aside 458 square kilometers for a National Wildlife Area, meant to preserve the local wildlife and fragile ecosystem.

The Cypress Hills rise 600 meters above the surrounding land and cover about 2,600 square kilometers, stretching across the Alberta-Saskatchewan border. Their highest point, Head of the Mountain, is 1,466 meters above sea level. It is the highest point of land between the Rocky Mountains and Labrador. The western part of the Cypress Hills lies within the SSRSB.

The southern boundary of the SSRSB lies on the boundary of two major river basins. The basin to the south is the Milk River Basin, which is part of the Mississippi-Missouri River system.

Read more about the geography of the South Saskatchewan River Basin (SSRB) (817.55 KB)


The population of the SSRSB is estimated at approximately 86,700 people (2016) residing in an area of 14,000 square kilometres, which translates into 6.2 people per square kilometre.

There are five Districts included in the SEAWA Basin (either entirely or partially), Cardston CountyCounty of WarnerCounty of Forty MileCounty of LethbridgeMunicipal District of TaberCypress CountyCounty of NewellSpecial Area No. 2, Special Area No. 3, and the Municipal District of Acadia. Major population centers include the City of Medicine Hat, the towns of Redcliff and Bow Island, the Village of Foremost, and CFB Suffield.

The population is predominantly urban, and the urban population is growing at a faster rate than the rural population. The largest urban center is Medicine Hat, which had a population of 63,260 in 2016.

Read more about the demographics and profiles of rural communities in western Canada. (2.05 MB)

Indigenous History

The SEAWA watershed primarily covers Treaty 7 and Treaty 4 lands within Alberta. Historically, these lands have been used by a variety of First Nations groups, notably: Siksika, Kainai, Piikani, Stoney-Nakoda, and Tsuut'ina as well as the Cree, Sioux, and Saulteaux First Nations. Additionally, the SEAWA watershed falls within the homelands of the Metis Nation in Region 3. This diverse indigenous history can be seen in place names, monuments, archaeological sites, and even the land itself. Traditional knowledge and practices contribute greatly to our understandings of the watershed.

Rivers and Reservoirs

South Saskatchewan River

Some of the major bodies of water in the SSRSB include Pakowki Lake, Milk River Ridge Reservoir and Many Islands Lake. Pakowki Lake is located about 100 km south of Medicine Hat and 30 km north of the U.S. border. It is an intermittent lake, and it has undergone cycles in water level which have lasted several years. In a 1996 study, its area was about 109 km2. Its only inflow stream is Etzikom Coulee, a long glacial spillway channel. Marsh habitat and sand dunes are located near the lake.
Several other notable bodies of water are in the vicinity of the SSRSB. Chappice Lake is a small saline lake located about 20 km northeast of Medicine Hat. It is less than one meter in depth. The lake used to be fed by a stream from the northeast, but in 1978 a weir was constructed in this location, preventing surface water from flowing in.

Elkwater Lake is located in Cypress Hills Interprovincial Park. Its outlet has been artificially deepened to increase water flow to the nearby reservoir.

Travers Reservoir is a man-made reservoir built on the Little Bow River, about 35 kilometers southeast of the town of Vulcan, with an area of 22.5 square kilometers. It was constructed in 1954 to store water from the Bow River. White Horse Lake, Dishpan Lake and Easy Lake are located in Canadian Forces Base Suffield, in the Middle Sand Hills area.

The St. Mary River Irrigation District is a large system of canals and pipelines covering over 150,000 hectares. A large part of this is in the SEAWA management area. The entire irrigation area is south of the Oldman and South Saskatchewan rivers, extending from Medicine Hat in the east to Lethbridge in the west.

Here is a list of lakes and reservoirs in the South Saskatchewan River Basin (SSRB).

Riparian, Wetland, and Protected Areas

The prairies of Alberta contain numerous wetland areas. Wetlands are places where the land has been saturated with water long enough to have poorly drained soils. Unlike lakes, some wetlands do not have well-defined boundaries, and some are not permanent. Most wetlands in southern Alberta are temporary, with water accumulating in the spring. Over 60% of the wetlands in southern Alberta have been drained.

The main types of wetlands located in central and southern Alberta are marshes and ponds. These types of wetlands differ by their structure and the wildlife which live there. Marshes (sloughs) form as water drains into depressions to create pools of still water which contain high levels of nutrients. Ponds are still-water basins which are wide and generally shallow. Water in ponds is accumulated from precipitation or groundwater sources. Ponds can undergo dry periods in the late summer.

Prairie marshes, also known as prairie potholes or sloughs, are depressions of about 30 to 80 meters in diameter which formed during recent ice ages. These potholes were later partially filled with sediments.

The SSRSB is part of the Prairie Pothole Region, a large area that covers much of southern and eastern Alberta, southern Saskatchewan, North Dakota and South Dakota. Many of these depressions resulted from melting glaciers. Prairie wetlands often act as groundwater recharge or discharge sites. Because the prairies experience wet and dry periods, some of the wetlands can dry up for several years. When this happens, different types of plants may begin to grow. Most depressional wetlands do not have inflows or outflows on the surface. Depressional wetlands that provide groundwater recharge tend to have lower salt content, and those that receive groundwater discharge tend to have higher salt content.

Read more about protected areas and regions in the South Saskatchewan River Sub-basin (SSRSB).

Master Agreement on Apportionment

The Master Agreement on Apportionment states that all eastward flowing streams are subject to apportionment. The Prairie Provinces Water Board (PPWB) administers the Master Agreement on Apportionment, signed on October 30, 1969 by Canada and the provinces of Alberta, Saskatchewan, and Manitoba.

The Agreement provides for an equitable sharing of available waters for all eastward flowing streams that cross interprovincial boundaries, including interprovincial lakes. It also serves to protect interprovincial aquifers and surface water quality. Schedules to the Agreement describe the role of the Board, stipulate how the water shall be apportioned, and set water quality objectives for the water passing from Alberta to Saskatchewan and from Saskatchewan to Manitoba.

Read more about Master Agreement on Apportionment.


Ecozone. Ecosystem. Ecosphere. Ecoregion. What’s the difference between all these “ecowords”? It’s all relative, starting with an ecosystem, which is a natural community that can exist anywhere on earth. Combining the word 'eco', which means habitat, and 'system', which refers to the interdependent way natural elements fit together, an ecosystem can be as big as the planet or as small as the palm of your hand. An ecozone is a relatively large ecosystem. And the ecosphere is the largest of them all.

An Ecoregion is an area of similar climate, physiography, vegetation, soil, water, fauna and land use characteristics. Climate strongly influences many of the other characteristics in an ecoregion, such as soils, vegetation, water, fauna and land use. In Alberta, ecoregions are called Natural Regions and each region is subdivided into Natural Sub-regions. The SEAWA watershed belongs to the Grassland Natural Region.

Learn more about Alberta's natural regions below:

Natural Regions and Subregions of Alberta - Alberta Parks

Map of Alberta's natural regions and sub regions.

Eco Regions and Zones (Click to enlarge)