The Water Security Agency (WSA) is warning Saskatchewan residents to be cautious around the South Saskatchewan River, as heavy rainfall will bring flows to a peak this week.

Southern Alberta and Saskatchewan were hit with significant rainfall over the weekend, with some parts of southern Sask. seeing up to 80 millimetres.

To prep for the rain, the WSA says the province of Alberta began releasing water from reservoirs to make room to store the incoming precipitation.

That reservoir outflow, coupled with the rainfall pouring into tributaries of the South Saskatchewan River over the weekend, will bring waters to a peak around June 26 this week between Alberta and Lake Diefenbaker — and other water bodies along the way.

Flows along the South Saskatchewan River are expected to increase from 100 cubic metres per second to around 830 cubic metres per second, the WSA said in a news release Friday.

Water levels in Lake Diefenbaker will rise approximately one metre in the coming days, the provincial water regulator says.

“Lake Diefenbaker has sufficient storage to capture the increases in inflows, but WSA will increase outflows on the South Saskatchewan to better manage the expected increases to lake levels at the reservoir.”

The water flowing from Lake Diefenbaker to Saskatoon is set to increase from the current rate of 65 cubic metres per second, up to 75, although the WSA said those were estimates that could change depending on rainfall intensity, duration and location.

Last month, the captain of Saskatoon’s iconic riverboat the Prairie Lily called on the WSA to release more water from Lake Diefenbaker to wash away the sandbars that are keeping him from setting sail for a final season on the water.

In response, the WSA said it was proceeding conservatively with the water, as the river has faced several years of below-normal runoff at its source in the Rocky Mountains.

Seasonal melt from the mountain snowpack along the Alberta and British Columbia border contributes 90 per cent of the water that flows downstream into Saskatoon, according to University of Saskatchewan hydrologists.

The WSA cautions residents to take sensible precautions around lakes and rivers.

“Be aware that flows and levels can change rapidly and without warning. Please check local conditions before venturing on or near water bodies.”