Whatcom County farmers use a lot of water every summer to irrigate their pastures and berry fields. But the public never knows just how much water irrigation uses. This means that governments make water-resource decisions using estimates instead of real data. These decisions include, as examples, drought planning and assessment of new water supply and efficiency options.
But that is a big problem because the estimates differ dramatically. For example, the high and low estimates of annual irrigation water use differ by four times the amount of water Bellingham uses each year (see Figure).
I examined several different irrigation-water-use estimation methods. These approaches differ on water use by crop, water use from year to year, and on the seasonal (month-to-month) pattern of irrigation water use.
These disheartening results suggest strongly that there is no substitute for metering irrigation water use. Absent such real-world data about working farms in Whatcom County, we have no way to address local water-resource issues.
My latest paper, How Much Water Does Whatcom Irrigation Actually Use? provides additional information on these comparisons and the five estimation approaches I considered.
Editor note: The report is attached as a easy to download and read pdf file. The report has formatting that we cannot duplicate online, such as footnotes and inline graphics. As a pdf, you can also download and print if you desire.