The Water Security Agency has announced that the Gardiner Dam spillway is scheduled to begin operating again today.  Recent rainfall and runoff continue to increase inflows into Lake Diefenbaker, with inflows forecast to peak around July 5 at approximately 2,000 m³/s before gradually declining.

As a result, Lake Diefenbaker is expected to continue rising steadily over the next 10 days, with reservoir levels forecast to increase by 1.25 metres.

Regarding planned spillway operations Thursday the total outflows are expected to increase 470 cubic metres per second. On Friday the outflows are expected to increase further to approximately 770 m³/s.  Typical outflows for this time of year are around 160 m³/s, making these levels significantly above normal.

The Water Security Agency in its latest update on Lake Diefenbaker forecasts the South Saskatchewan River downstream of the dam to the City of Saskatoon will also rise and see an increase in velocity.  This increase will cause the South Saskatchewan River to rise roughly two metres(m) through Moon Lake and 0.8m in Saskatoon. The WSA says flows at this level can pose a serious safety risk for residents and recreational users in and around the water at this time of year.

The spillway is being opened again because of significant rainfall in Alberta last weekend and into the beginning of the week and the WSA says spillway operations are anticipated to continue from July 3 to July 25, with outflows then being gradually reduced to 270 m³/s.  But they may need to increase the outflow again if there is further rainfall and increased inflows to Lake Diefenbaker.