Geography Reference
In-Depth Information
Figure 11.15. Non-contributing
areas of drainage basins as delineated
by Prairie Farm Rehabilitation
Administration, Agriculture and
Agrifood Canada and three Prairie
Provinces.
Non-contributing Areas
200
100
0
200
400 km
conditions depressions connect to one another through the
'
Drainage networks in the region are poorly developed
due to the post-glacial geomorphology, in which large
areas are internally drained, and the dry climate ( Figure
11.15 ). The northern fringe of the Prairies is covered by
Parkland, which was a mixed deciduous forest, wetland
and grassland complex that has been largely cultivated to
cereal grains and oilseeds or converted to pasture since
European settlement over 100 years ago. The region is
characterised by relatively low precipitation, especially in
the south-west part, due to the atmospheric flow barrier
imposed by the Rocky Mountains, and experiences fre-
quent water deficits and low soil moisture reserves. Annual
precipitation in the prairie region of Saskatchewan ranges
from 300 to 400 mm/yr, about one third of which occurs as
snowfall. This is a cold region and it exhibits classic cold
region hydrology with continuous snow cover and frozen
soils over much of the region in the winter. Great variation
in hydrology exists across the Prairies, with fairly well-
drained, semi-arid basins in the south-west part and with
many wetlands and lakes in the Parklands of the sub-humid
north, central and eastern parts.
Much of the region is cultivated and devoted to the
growing of cereal grains and oilseeds, with forage crops
where soils are less suitable for cultivation. Most runoff
occurs from spring snowmelt as a result of frozen soils and
rapid release of water from snowpacks (Gray et al., 1985 )
mechanism and can contribute to larger basin
runoff and large-scale flooding. During droughts, many wet-
lands and dugouts dry out completely, causing waterfowl
populations to crash due to lack of habitat and reductions in
livestock due to lack of dugout water. While on-farm water
supplies can be supplemented bywater hauling, this is expen-
sive and contributes to the failure of farms. For instance, the
prairie drought of 1999
fill and spill
'
2005 was very severe and is
regarded as the most expensive natural disaster in Canadian
history, with the period 2000
-
1 being one of the worst on
record (Bonsal and Regier, 2007 ). The gross domestic prod-
uct dropped $5.8 billion, agricultural production dropped
$3.6 billion and employment dropped by 41 000 due to the
drought at its peak in 2001
-
2(Stewartet al., 2011 ). The
number of prairie wetlands was the lowest on record.
Methods used to index agricultural droughts and soil mois-
ture are not suited for characterising hydrological drought as
it affects depressional storage in this region because they
cannot estimate runoff from the small ephemeral drainage
systems that feed these wetlands and dugouts. Estimating the
variability of runoff into these ungauged internally drained
basins has posed a considerable scientific challenge of great
societal interest in the region.
-
Description of the study area
The Canadian Prairies cover the southern part of the prov-
inces of Alberta, Saskatchewan and Manitoba and are the
northern limit of
-
the redistribution of snow in winter controls meltwater
generation for runoff production. Summer runoff gener-
ation is usually negligible because of deep soils
the North American Great Plains.
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