Manitoba Water Stewardship

Rainfall for the past few days has ranged from 25-50 mm in most areas of southern Manitoba The heaviest rain fell in the area from the upper Pembina River to just east of Brandon and toward Lake Manitoba where 50-75 mm fell late Monday to early Tuesday. Rainfall during the 24 hour period ending this morning was heaviest in the upper Assiniboine watershed from Russell to Yorkton. Most of the watershed upstream of Shellmouth Dam has received 25-50 mm of rain in the 48 hour period ending this morning. A nearly stationary upper low is expected to bring another 15-20 mm or precipitation to most of the watershed upstream of the Reservoir before the storm dissipates on Friday. Some of tomorrows precipitation may be in the form of snow. Winds at Shellmouth Reservoir are expected to be moderate northerly for the next few days.

A FLOOD WATCH FOR THE ASSINIBOINE RIVER FROM SHELLMOUTH TO MILLWOOD CONTINUES.

Rainfall upstream of Shellmouth Reservoir during the past few days has been much greater than expected and is producing significant amounts of runoff. Inflows to the reservoir have increased and will result in further rises of the reservoir water level. It now appears that it may not be possible to keep outflows at 1700 cfs. This should become more apparent by tomorrow when more is known about rainfall and runoff.

The water level of Shellmouth Reservoir rose to 1410.30 feet this morning, in large part due to rainfall on the reservoir surface. The total outflow was increased to 1750 cfs this morning of which 300 cfs was flowing through the conduit. The inflow for the 24 hour period ending this morning, including rain on the reservoir, was 2400 cfs. Flows from the local drainage area around the reservoir as well as for the Shell River and the Assiniboine at Kamsack will rise during the next few days and remain relatively high for the next week or so. The conduit flow will be reduced to zero as the reservoir level and spillway flows rise, but it appears that spillway flows may reach 1800 cfs or more, depending in the amount of additional rain and runoff.

Rainfall in other areas of southern Manitoba has caused minor rises in most streams. Some small streams in the band of Monday night’s heavy rain from the Turtle Mountain area to west of Brandon and toward Langruth may have experienced some flash flooding for a little while. The rainfall raised Pelican Lake by a quarter foot or so and has required regional MIT staff to release about 100 cubic feet per second from the Lake via the controlled outlet channel. This should bring the lake back down to its target level by early next week.

Rainfall in recent days has also caused streams flowing into Red Deer Lake to rise, but the rise in the lake level should be limited to about one-third of a foot leaving the lake well below the crest observed in early May.

Rainfall in the Whiteshell area was in the 15-20 mm range and will produce little runoff. It is unlikely that dams will need to be operated to reduce lake levels

Red Deer Lake:

Levels of these streams continue to decline. The decline in the Saskatchewan River will continue to be very slow until the end of May. High water levels at The Pas will continue to require pumping from the Pasquia River since gravity flow cannot occur until levels decline significantly further.

This is the last report of this series for the Red Deer, Carrot and Saskatchewan River systems for the spring of 2007.

A flood sheet for the Swan River area is not available for today.