Blue, green and virtual water, comparing irrigation water requirements in the driest watershed in Canada
By Prof. Hans Schreier, Institute for Resources and Environment, University of British Columbia
The Okanagan Basin in British Columbia is one of the driest watersheds in Canada. Because of its relatively favorable climate it is home of some of the best orchards and vineyards in the country. The basin has experienced one of the fastest population growths in Western Canada and it is also a very favored recreation destination for swimming, golfing, boating, skiing, fishing and wine tasting. Concerns about water supplies have long been a major issue but this became most apparent in 2003 during a very hot summer when forest fires ravaged the area. The Okanagan Water Board has embarked on a comprehensive determination of the overall water balance in the basin and the B.C. Ministry of Agriculture and Land, in collaboration with Agriculture and Agri-Food Canada, took on the responsibility to determine the irrigation water use of all crops grown in the basin. This consisted of a GIS based field inventory of all agricultural fields that included crop type, soils and type of irrigation systems, and
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climatic conditions. Detailed crop water requirements were determined for all crops grown in the 104’000 different fields surveyed in the basin and also included water requirements for the 45 golf courses. This is the first time that such a comprehensive determination of water requirements for food production has been completed in a major river basin in Canada. |
The fascinating part of this analysis is the fact that we now have an excellent way of comparing the blue and green water requirements between different crops. There are very large differences in water needs between different fruit orchards, forage crops, vegetables and golf courses. It also allows us to determine the differences in water requirements between wet and dry years and this will form the basis for scenario developments in view of increased climatic variability.
While the B.C. Ministry of Agriculture and Land, and Agriculture and Agri-Food Canada were responsible for the land use inventory and water requirement modeling, the grant provided by the Walter and Duncan Gordon Foundation enabled researchers and students from the University of British Columbia to collaborate with the agricultural agencies to determine the agricultural trends and water requirements over the past 15 years. These results will become part of the overall water balance determination of the basin which includes domestic indoor
and outdoor water use, industrial
use and agricultural requirements. It will also address the water
supply conditions and partition what water originates from groundwater
and surface water. The Okanagan Water Board will greatly benefit
from this initiative because they are given the mandate to determine
future water needs and how to arrive at a sustainable rate of
water management in view of continuing growth and recreational
expansion. |
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To view the Virtual Water in the Okanagan Watershed report, please click here.