The years 2015 to 2018 were challenging ones for water management in the South Saskatchewan River Basin.
Water supplies were below average and so was precipitation.
“Overall, the water supply has generally been five years of consecutive below-average runoff in both the Oldman and the Bow river basins,” said Alberta Environment resource manager Brian Hills.
He discussed water supply management challenges Feb. 4 at the Alberta Irrigation Districts Association water conference in Lethbridge.
In three of the last five years, mountain snow pack that supplies water to much of southern Alberta and beyond has been below average. Only 2017-18 had above-average levels.
Rainfall recorded at stations monitoring the Bow and Oldman rivers over the last five years was above average in 2019, below average in both 2017 and 2018, and much below average in 2017, said Hills.
“(Low precipitation) has presented some challenges to us,” he added.
“That leads to high levels of water demand for the allocation that we have in southern Alberta, where we have thousands of licensees and registrations that have an opportunity to … obtain water and divert water and the majority of that in the south is tied to irrigation.
“The other large demand is our municipal demand from our communities to supply drinking water and water for their needs.”
Those demands lead to worries about having enough water to support aquatic ecosystems in the region.
In four of the last five years, spring runoff has occurred earlier than the average and was followed by low rainfall.
“We’re seeing stream flows decline to late summer, early fall levels early in the summer, by mid (or) late June often, so that has repercussions for the aquatic ecosystems.”
Hills outlined standard management responses in times of water supply issues. The first stage of monitoring and storage checks is followed by placing conditions on licence holders and cancelling temporary diversions. Fisheries advisories and closures might also occur.
The final stage, never experienced, would be to have provincial cabinet issue an emergency declaration and decide who gets whatever water is available.
Within the last five years Hills said the environment department several times has suspended or cancelled temporary diversion licences and implemented water shortage response plans in some areas.
However, Alberta has always been able to meet its transboundary water supply obligations to Saskatchewan.
“The latter half of July and (all of) August are the periods when we see the most amount of management actions and issues,” said Hills, because that is when irrigation demand is high, river flow is low and there is potential stress on aquatic life in waterways.