Water from Manitoba's swollen Assiniboine River flowed through a break in the dike system and across prairie flatland after the province acted on a controversial plan to intentionally flood one swath of land to save another.

Excavators used heavy machinery to scrape away a layer of rock near Hoop and Holler Bend, northeast of Portage La Prairie, at about 7 a.m. local time, allowing a trickle of river water into an area that had previously been protected by sandbags.

The province said in a statement that it would take several hours before a "significant amount" of water was flowing through the dike breach.

By Saturday afternoon, the flow was spreading slowly across prairie fields and filling ditches along roads. The plan was that the water would disperse from the Assiniboine River and into the LaSalle River watershed.

The intentional breach was expected to inundate a 225-kilometre area that is home to 150 homes and farms.

As of Saturday afternoon, Premier Greg Selinger said that water had extended "about a mile" over farmland from the breach.

He added that homes in the flood path were "well-protected" by dikes, and added that "we've been able to, so far, manage it."

The controlled breach is designed to avoid an uncontrolled break that could devastate as many as 850 more homes and more than 500 square kilometres of land.

"Up to now, things have gone very well," Selinger told CTV News Channel from the scene of the flooding.

He also expressed confidence that the federal government would take part in extra compensation for property owners in the area of the breach. But he added that if the province had not created floodways and dikes in years previous, the entire area would already be under "five feet of water."

Earlier in the day, a provincial media release stated that the "controlled spill floods approximately 225 square kilometres in order to prevent flooding of a much larger area with up to about 10 times the volume of water from an unplanned dike breach.

"The controlled release affects the same area that would be at risk of flooding by an uncontrolled breach."

The breach was originally scheduled for Wednesday but was repeatedly delayed, in part because of recent improvements to the Portage Diversion, a man-made channel that runs water from the Assiniboine north to Lake Manitoba. The Diversion was designed to handle 25,000 cubic feet per second but, following hasty efforts to expand it, is now managing 33,000 cubic feet per second.

The dike breach at Hoop and Holler Bend started releasing an estimated 500 cubic feet per second, enough water to fill an Olympic-sized swimming pool in three minutes. The rate of release will increase until it reaches 3,000 cubic feet per second.

Although that sounds like a lot of water, officials said its dispersal over a large, flat area means there won't be a catastrophic deluge.

Lt.-Col Shane Schrieber said there were 1,300 soldiers from the Shilo, Man., army base and across western Manitoba working in the region to maintain and build dike and sandbag systems.

"We have focused our efforts on armouring the dikes along the Assiniboine River so we can maintain the flow rate," Schreiber told CTV News Channel. "We have also been preparing houses in the inundation area by the Hoop and Holler Bend to get them ready for whatever inundation might come."

He said soldiers would work "one or two days ahead" of the water flow in an attempt to shore up homes before the flows arrive.

The provincial government has said it will look to improve flood-proofing along the Assiniboine once the waters recede -- possibly expanding dikes or increasing the capacity of the Shellmouth reservoir system.

The federal and provincial governments have spent almost $1 billion since the so-called flood of the century in 1997 to improve flood protection along the Red River.

Selinger said that officials had built the flooding system to handle water flows two-feet above previously recorded high marks. But he conceded that this year's floods had exceeded even the worst-case scenario.

"The reality is, it's been a real shock to everybody," he said, adding that the floods have been called a "one in 300-year event."