These are graphs of break-up and
freeze-up dates for three rivers that drain to West Hudson Bay.
The Dubawnt River is breaking
up earlier in the spring and freezing later in the fall. The timing of break-up
and freeze-up have not changed for the Kazan River and the Cochran River over
the same time period.
The distance between the break-up
and the freeze-up lines on the graph is the length of the open-water period.
The open water period for the Dubawnt River has increased (on average) about
50 days from 1968 to 1995. To see this more clearly, here is the number of
open water days for each year for the Dubawnt River:
The timing of fall freeze-up and
spring break-up depends on weather conditions in the river basin in fall,
winter and spring. Long-term trends in these weather conditions can be expected
to affect the river's ice conditions.
Timing of spring break-up and
of fall freeze-up affects nesting waterfowl, river crossing and travel conditions
for people and migrating caribou, and conditions in the river such as growth
of algae.
The length of the ice-free season
affects summer habitat for animals using open running water.
Source: Environment
Canada 1999. HYDAT version 98 - 1.05.8. Surface water and sediment data. CD-ROM.
Water Survey of Canada/Meteorological Service of Canada.
Click to see a table of monitored rivers in the Beverly and Qamanirjuaq range:
Red trend lines on the
Dubawnt R. graphs are highly significant linear regression lines (p<0.01).
