|Tthe basin of the Bow River, a remarkable tract of land that extends from the Rocky Mountains, across foothills and the rapidly growing City of Calgary, to the broad prairie. This land has been home to First Nations for thousands of years. Within this basin, all waters flow into the Bow River. We share this water with plants and animals. Without this water, nothing could live. With this water, a great diversity of life, including humans, can thrive. As residents of the Bow River basin, they must protect the land that produces the life-giving waters. They face many challenges. Their rapidly growing population demands much of the land and water. Our climate is changing and the future of our water supplies is uncertain. To act wisely, we need first to understand our basin. The purpose of this poster is to introduce us to the local water cycle, to how humans use the basin waters, and to how we can live well on the land.|
Where does the Bow River Go?
|The Bow River joins the Oldman River near Medicine Hat to form the South Saskatchewan River. Bow River waters flow all the way to Hudson Bay. Downstream communities that use these waters, such as Medicine Hat and Saskatoon, depend on us to care for the quality of the water as it passes through the Bow River basin.|
Bow River Basin
|A river basin or watershed is high at its edge and low in the center where the river flows. The Bow River basin or watershed includes all the land that feeds water to the Bow River and its tributaries.|
Mountains, foothills and prairies
|Most Bow River waters come from the Rocky Mountains, an area largely protected within parks. East of the mountains, the Bow River flows through foothills and then through rolling prairie. The Bow River also flows through the City of Calgary, home to most of the basin’s human residents.|
|The Bow River basin is the most densely populated river basin in Alberta. Less water is available per person there than in any other river basin in the province. And yet, in the last ten years, the population of the basin has grown by over a quarter of a million people.
The lands of the Bow River basin have been home to First Nations people for thousands of years. Today, the Stoney Nakoda Nation has reserve lands throughout the foothills of the Bow River basin. Tsuu T’ina Nation reserve lands extend west from Calgary to Bragg Creek, and Siksika Nation reserve lands straddle the Bow River valley near Bassano.
So effective are the Rocky Mountains at stripping moisture from eastward-moving air masses that little is left for the prairie areas, creating a ‘rain shadow’. This is why irrigation is vital to agriculture. The Bow River is the only dependable source of water.
Sources of Bow River water
|Water flows the entire length of the Bow River in less than two weeks. Why then doesn’t the Bow River dry up between rainstorms? Because nature stores and slowly releases water throughout the basin. Water is stored in snow packs, glaciers, wetlands, and aquifers.
Almost all the water in the Bow River comes from the Rocky Mountains. This mountain chain forces air to rise and cool, causing moisture to condense and fall as rain or snow. This precipitation, together with the melt waters from glaciers that release ancient snowfalls, feed the Bow River through its many mountain tributaries. Even groundwater that feeds the Bow River begins its life as rain or snow.
|Many people wonder what will happen to the river if the glaciers melt away. In fact, glacier melt waters contribute less than 1% of the total annual flow to the Bow River so their overall contribution is small. However, the portion of Bow River water derived from glaciers rises during the summer as snowmelt wanes. During a drought year with reduced snowfall and rain, the relative contribution of glacier melt water to the Bow River is higher. Without glaciers in the Bow River basin, water supply during drought years would be much more challenging. However, as long as it snows and rains every year, we can expect the river to keep moving.|
Ground Water ~ the Hidden Reservoir
|Rain and snowmelt infiltrate the ground. Soil and rock act as giant sponges full of tiny pores and cracks that are usually less than millimetres in size. Below the water table, these holes are full of water. This is groundwater. Groundwater slowly travels through connected pores and cracks, just centimetres to hundreds of metres per year. Any rock or sediment that yields useful amounts of water is an aquifer. The volume of groundwater below them dwarfs the volume of water stored in glaciers, lakes, wetlands, and rivers.
Groundwater and surface water are one connected water system. Water wells intercept groundwater that may be on its way to springs that feed streams and rivers.
In southern Alberta, oil and gas drilling has shown that groundwater is found to depths of four kilometres or more. However, most of this groundwater is very salty. Only shallow groundwater is potable or fit to drink.
The Bow River and Climate Change
Sharing Bow River Water
|Some water use occurs in the river, such as by wildlife and for fisheries and recreation. Some water is withdrawn from the river, used, and returned (non-consumptive use). Municipalities return over 90% of the water they use as treated sewage. Some water is withdrawn from the river and not returned (consumptive use). In dry years, irrigation returns about 20% of what it withdraws. Most of the rest is used by plants, whereas some evaporates and a small amount sinks into the ground. Withdrawal of water from the river reduces river flow and can have an impact on wildlife habitat in and along the river.|
Down the Drain
|There is a widespread myth that water that goes down storm drains flows to water treatment plants. This is not true. Storm drains are only meant for rainwater and snowmelt. Many street drains flow through pipes straight to the river.|