HIGH RIVER, Alta. - Residents affected by flood warnings in southern Alberta are being warned to clear out their basements, while city crews in Calgary have begun placing sandbags along the banks of the swollen Elbow River.

Alberta Environment issued a flood warning for the Highwood River on Saturday, prompting the town of High River south of Calgary to declare a state of emergency in preparation for the river's expected crest on Sunday afternoon.

A flood warning was also issued Saturday on parts of the Elbow River, which flows through Calgary. Flood warnings were then added late Saturday for Sheep River, including the towns of Black Diamond and Turner Valley, and for Threepoint Creek.

The province says it expects another 30 to 50 millimetres of rain to fall in the region, raising some rivers to the tops of their banks.

The Calgary Fire Department issued a media release Saturday warning that the increased flow on the Elbow could be dangerous for people who get too close to the banks.

But the situation appeared to become more urgent late Saturday night when the city issued a media release stating that it was placing sandbags in what it termed "critical areas" along the river.

The city warned that storm sewers might overflow, and that homeowners along the river should minimize potential flood damage by capping sewer floor drains, and not to sleep in basements until the river level recedes.

Calgary residents were also warned to stay away from the banks of the Bow River, where a high flow advisory has been issued.

The heavy rain in southern Alberta prompted the Saskatchewan Watershed Authority to issue a high stream flow advisory for the South Saskatchewan River, which flows into the province from its western neighbour.

The authority says that early projections suggest the portion of the river between the Alberta boundary and Lake Diefenbaker river could rise by as much as two metres by Thursday.

Alberta authorities noted recent warm weather was adding to the troubles by melting snow in the mountains.