||May/June 2003 issue||
What a difference a year makes: satellite images reveal drought’s impact on
Alberta farms and ranches
By Steven Fick and Eric Harris
dry weather has depleted water resources across Western Canada for the past
three years. Last summer, many municipalities in the southern Prairies were
declared disaster areas. Two satellite images (below) of the same farmland — one
from relatively rainy July 2001; the other from dry July 2002 — provide
a graphic impression of drought near Wainwright in eastern Alberta, which suffered
its driest period in almost a century.
Captured by sensitive scanners on Landsat-7, the 2001 image shows "healthy
vegetation and crops with a biomass content somewhat less abundant than in
a normal year," according to Carolyn Goodfellow of the Canada Centre for
Remote Sensing. The parched-looking 2002 image shows vegetation with low chlorophyll
content and healthy vegetation limited to where plants access water: along
the Battle River and around creek beds, marshes, potholes and dugouts. Small
and shallow lakes seen in 2001 are dry with fringes of vegetation in 2002.
The drought’s cause? Shifts in atmospheric circulation influenced in
part by unprecedented warmth of the western Pacific Ocean, according to scientists
at the National Oceanic and Atmospheric Administration in the United States. "The
decades-long oceanic warming trend, likely a result of global warming," they
report, "may be a harbinger of future severe and extensive droughts."