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.

The sources of Bow River water ~20% rain + groundwater + glacier melt ~80% snowmelt larger image [JPEG, 274.6 kb, 1075 X 810, notice]

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 snowpacks, 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 meltwaters 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.

Late spring snowpack at Bow Lake, Icefields Parkway, Banff National Park. Mountain snowmelt feeds water to the Bow River during spring and summer. (R.J.W. Turner, GSC 2005-197)

Many people wonder what will happen to the river if the glaciers melt away. In fact, glacier meltwaters 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 meltwater 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.

Meltwater from the Bow Glacier feeds the headwaters of the Bow River. (Courtesy of Parks Canada)