Influence of glaciers on streamflow

The map shows the location of glaciers and ice caps and also indicates the rivers and the lakes, which are fed by a glacier (or an ice cap) meltwater. The purpose of this plate is to identify those streams which are fed by glacier meltwaters. Because of the scale of the map, many minor glaciers have not been shown and, hence, streams fed by such glaciers are not depicted as being glacier fed. The proportion of glacier-derived to non-glacier-derived water decreases as one goes downstream from the glaciers. The map shows many short streams in the Arctic islands and in the mountains of western Canada which are affected by glacier melt. However, the lower reaches of long glacier-fed streams, such as the Mackenzie and Columbia Rivers, are affected very little by the presence of glaciers within their catchments.The 20th century has witnessed the shrinking of many glaciers. The release of this water from storage has produced higher discharges from many glacier-fed streams than would be expected from precipitation alone. In catchments that are about 50 per cent ice covered, loss in ice volume from one year to the next can contribute as much as 20 per cent to the annual stream discharge. Even on a large river such as the Columbia at the Canada-United States border or the North Saskatchewan River near Edmonton, mean annual flow may have been increased by 2 to 4 per cent by reduction of ice volume within the catchments.