We have a better chance of water replenishment

In January 2014, I visited the Hoover Dam as I had done off and on since 1983. It was built in the 1930’s and was filled to a level of 1221.40 ft above sea level – FSL (Full Storage Level) right after the construction was concluded in 1935. The lake/reservoir level is currently about 156 ft. below the FSL (1067.86 and dropping). The water held by the Hoover Dam is apportioned mostly to California, with about 20 per cent to Nevada and a small percentage to northern Mexico through the Rio Grande River below Lake Havasu. I mention these commitments as they are all licenced through outflows from the Colorado River and are available for viewing at the USBR (United States Bureau of Reclamation website). On my 2014 visit, I mentioned aside to the tour guide from USBR that “You don’t have a water supply problem in the Colorado Basin – You have a water use problem”. He brought me in front of the tour group and said “This Canadian hydrologist says that “See above”. Reading today’s online articles about the water supply problems downstream of Lake Mead, they are finally getting the point – probably about 20 years too late.

Putting the above in perspective for us in southern Alberta, we are currently in a fairly good position for water supply for irrigated crops and municipal water use for 2021 because of our water storage reservoirs. Those flows may be somewhat limited in certain municipalities that aren’t directly downstream of reservoirs. I notice today that the flow at Lethbridge is at 23 cms which is slightly above the 20 cms minimum flow requirement.

That additional flow may be a part of the downstream license obligation to Medicine Hat and to Saskatchewan at the provincial border. On a note from me, if the Oldman Dam had not been built, the flow in the Oldman River might be down to the low flows during the ‘80s where you could wade across the river in gumboots.

On a final note, the flows from the Continental Rockpile along the B.C. border as far north as Grande Prairie are up to 40 per cent below average and dropping. Although these flows are augmented by glacial melt and snowmelt, the snow has long since melted and the glacier outflows are already waning. Bottom line, it’s a good thing that we don’t have 40 million folks to supply fresh water to as is expected in California for all their swimming pools and golf courses, not to mention the Imperial Valley agricultural output.

Also, we probably have a better chance for a winter replenishment of snow to look forward to after October for spring refilling of our reservoirs – I hope!

Dick Allison, Hydrologist

Lethbridge