Emergency crews in Medicine Hat have prepared for the worst as water levels in the city’s major river continue to rise and are expected to peak Monday morning.

The water flow in the South Saskatchewan River is projected to top 5,000 cubic metres per second on Monday. Similarly high flows in the river in 1995 caused widespread damage across southern Alberta.

Flooding on the Bow and Elbow Rivers devastated parts of Calgary on Thursday and Friday, and more than 20 communities in Alberta have been on alert after heavy rains.

Approximately 10,000 people have been asked to leave the low-lying areas of the city as the South Saskatchewan River continued to rise over the weekend.

Volunteers sandbagged areas around city hall and the downtown core in preparation for the high waters.

Soldiers have also worked to build a dyke around the city’s drinking water treatment plant.

“Both the water treatment plan and power plant continue to be protected by berms,” Ron Robinson, the city’s director of emergency management, said at a news conference. “Our drinking water is safe.”

On Sunday, the water flowed higher than most people in the city had ever seen.

“I worked the flood in ‘95 and it was really bad then,” resident Kevin Elderkin told CTV News. “They say it's supposed to be twice as bad, if not three times as bad (now). It's hard to fathom.”

Despite early sandbagging, some low-lying parts of the city experienced flooding.

“We thought we had a good job there with the sandbagging but as it turns out when the water started to come in it sort of washed itself right in,” Medicine Hat Mayor Norm Boucher said at a news conference.

Waters levels on Sunday forced the city to close two of its bridges. They’re asking residents not to use the third.

“Residents must stay away from the Trans-Canada Highway bridge unless absolutely necessary,” Robinson said.

Heavy equipment is in place to keep debris from piling up against bridge decks.

Though many people have voluntarily left their homes, some have refused to follow evacuation orders, Robinson said. He warned that these people could be arrested.

“There has been some strong language used under the emergency management act,” Robinson said at a news conference. “People can be arrested where needed.”

The swelling river has some residents preparing for the worst.

“We’ve moved all the furniture upstairs in the house,” one resident told CTV Calgary. “And we’ve got sandbags in front of the house.”

The city has started setting up emergency shelters for displaced residents.

Across the province, 27 communities in Alberta are under a state of emergency.

In High River, where large parts of the town remain under water, at least three people have died as a result of flooding. A fourth person remains missing.

With files from CTV Calgary’s Bill Fortier