2009-06-21_1317Climate Change is expected to have an impact on temperatures and rainfall in much of Canada, but beyond climate change, there are also seasonal droughts, that people are quick to point the finger at the global problem, but often are just part of the cycle of things. It has been said that the inherent variability of temperature and rainfall is greater than the immediate effects of Climate Change, certainly this might not be the case in the future, but for now, we should be aware of the problem, but stop trying to label everything as an example of climate change!

One site that I’ve followed for information is the Drought Watch Website produced by Agriculture and Agri-Food Canada.

=2.00 Extremely Wet
1.60 to 1.99 Severely Wet
1.30 to 1.59 Moderately Wet
0.80 to 1.29 Slightly Wet
0.51 to 0.79 Incipiently Wet
-0.50 to 0.50 Near Normal
-0.79 to -0.51 Incipiently Dry
-1.29 to -0.80 Mildly Dry
-1.59 to -1.30 Moderately Dry
-1.99 to -1.60 Severely Dry
<=-2.00 Extremely Dry

The Standardized Precipitation Index can be thought of as the number of standard deviations that the precipitation value of interest would be away from the mean, for an equivalent normal distribution and adequate choice of fitted theoretical distribution for the actual data. The result of the SPI, can be interpreted as a probability using the standard normal distribution (i.e., users can expect the SPI to be within one standard deviation about 68% of the time, two standard deviations about 95% of the time, etc.)

Drought Watch Website

2009-06-21_1318To put this data into perspective locally, have a look at the zoomed in view to the left showing the yellow to red areas in the Southern Interior of BC and right across Alberta.

Additionally, check out the snow pillow data for Redfish Creek near Nelson, BC from the Water Stewardship Division. This has only had data collected since 2001, so there is limited data for determining real trends. Considering in 2003 there were some serious drought conditions across BC, contributing to fires and water shortages; the graph below, if accurate, should be of concern considering there is 8 years of data in the maximum, minimum and average curves and this year is well below the minimum from the previous eight years.

2009-06-21_1330You can find out more about snow pillow measurements here.

The rest of the summer can hold wet weather or dry, and for many local watersheds that can mean the difference between water restrictions or having plenty. For the Arrow Lakes system to the North of Castlegar, it has already been announced that the lake level will not be raised for the start of summer due to lower than normal flows.

I’m no expert in meteorology, but this information does interest me and is part of the information I use as the manager of a water supply system to plan system works over the summer months. Here’s a recent article from teh Globe and Mail on the extent of the drought on the prairies:

In portions of the hardest-hit region, which stretches in a triangle pattern from Saskatoon to Edmonton and Calgary, 2009 marks the driest spring Agriculture Canada has seen in the 70 years records have been kept in the area.

The arid soil, combined with record-cold temperatures, have killed many cash crops and left ranchers with pastures of brown stubble to feed cattle.

Producers say the circumstances are ominously comparable to those of 2002, when much of the Prairies grappled with the worst drought in 133 years. Farm incomes sunk by 70 per cent in some regions and growers as far away as PEI shipped their hay to desperate western cattleman.

Alarm Bells Ring on Drought “Disaster” – Globe and Mail

Published by Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of UrbanWorkbench.com and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada.