Much has been said recently about water in the Okanagan Basin. I was appointed to sit on the Okanagan Basin Water Board as part of my external committee work and have learned much in the past year.
As should be obvious to most residents, the central issue concerning water in the Okanagan Basin is that we do not get much precipitation to replenish water that leaves the basin. It is important to recognize, however, that the biggest losses of water (by far) are due to natural evaporation from the lake surface and evapotranspiration from trees and other vegetation. Indeed, losses of moisture to the atmosphere accounts for 85% of the precipitation that falls in the basin. Of the remaining 15% for human consumption, 70% is used for agriculture. Thus, direct human consumption accounts for only 4.5% of the water in the basin. Moreover, a good portion of this remains in the basin. For example, when a resident within a municipality flushes a toilet or does a load of laundry, most of the water is returned to local lakes and rivers following sewage treatment. Septic losses are higher due to evaporation; however, some portion of water sent to a rural septic tank eventually infiltrates and replenishes local groundwater.
The purpose of the OBWB's water supply and demand project is to better understand these different flows and collect some precise numbers to replace the rough estimates above. But the basic point is this: human consumption is not the existential threat to the valley's water resources that is sometimes assumed. This is not to say that we have ample water. We clearly do not. But these numbers do suggest that we have bigger fish to fry than low-flush toilets when we consider water conservation.
Two links of interest:
- A good overview of water issues in the Okanagan from the Natural Resources Canada: http://geoscape.nrcan.gc.ca/h2o/okanagan/water_e.php
- A paper outlining blue, green, and virtual uses of water in the Okanagan Valley: http://www.gordonfn.org/FW_obj1_project-15.cfm