Environmental Trends 2002

Climate Change

What is the Relationship Between Climate and River Flow?

Timing of 1/3 of Fraser River Annual Flow (1913-1998)

SOURCE: Data from the Canadian Historical Homogenized Temperature Datasets. Analysis by Canadian Institute for Climate Studies, 2001, for Ministry of Water, Land and Air Protection. NOTES: All values are statistically significant at the 95 percent level. All trends are positive and indicate warming.

What is the relationship between climate and river flow?

• A larger part of the total annual flow of the Fraser River is occurring earlier in the year than it did 90 years ago. The date by which one-third of the cumulative flow now passes the town of Hope has advanced at a rate equivalent to 11 days per century. The date by which one-half of the annual cumulative flow occurs has advanced by 9 days per century.

• Most of the streams and rivers that contribute to the Fraser River system are dominated by snowmelt. Warmer spring temperatures and earlier melting of snow and ice will result in more water flowing through the river system earlier in the year, with less water available in the summer and fall.

• Lower river flows are associated with warmer river temperatures, and reduced water quality, with potential impacts on aquatic ecosystems, and domestic water supplies.

For detailed information, including graph data, see In-Depth report.