Authorities are intensifying patrols on rivers and lakes across the metro area and state this July 4th weekend, which promises to be one of the busiest boating weekends in a year that is shaping up to be a deadly one on Minnesota waters.

Nowhere is the boating scene — and drunken boating issues — bigger than on Lake Minnetonka, where at least 40 officers are being deployed across the lake, including, for the first time, the party hot spot of Big Island.

In addition, ambulances now will be stationed on shore, and the Hennepin County Sheriff’s Office is opening a new boat launch on the lake to handle emergencies.

“This gets to be a rowdy weekend,” said Melissa Waskiewicz, who represents Lake Minnetonka’s homeowners association. “And we’re all bracing for what’s to come.”

So far in Minnesota this year, eight people have died in boating-related incidents — the highest number at this point in the season in at least the past 10 years, according to the Department of Natural Resources.

Locally and nationally, alcohol is the No. 1 factor in boating fatalities and accidents.

On last year’s July 4th weekend, authorities responded to 75 emergency calls on Lake Minnetonka. Medical calls came in nonstop one afternoon: unconscious drunken boaters, a woman whose leg was cut when a boat backed into her, a man who sustained a spinal injury after diving into shallow waters.

“Clearly last Fourth of July we had significant issues,” said Hennepin County Board Chairwoman Jan Callison, who represents the Lake Minnetonka area.

The 14,000-acre lake, the state’s most popular, typically winds up with about half the entire state’s boating while intoxicated citations each year. Even so, last year was unusually busy there.

Because emergency crews couldn’t land close to shore to bring patients to ambulances or helicopters, Hennepin County last month built a $125,000 emergency access and dock in view of Big Island, east of the ­Arcola Bridge. It shortens the distance for crews shuttling patients to ambulances stationed there.

“Hopefully, it will be a nice, safe weekend,” Sheriff Rich Stanek said.

‘Night and day difference’

Enforcement also is ramping up this year, with the DNR and Sheriff’s Office running 11 boats on the lake — up from eight boats last year.

“I think they’ve sent the message that they’re out there looking,” said Jay Green, who heads the board for the Lake Minnetonka Conservation District, which regulates use of the lake and helps fund some of the patrols. “This weekend’s going to be the real test.”

There will be a dedicated deputy on the lake, a measure begun last year. Fire departments will offer use of their boats as reinforcements. And for the first time, Orono police officers will be stationed on the shore of Big Island to cite boaters who trespass or litter on private property or parkland. Partygoers typically leave beer bottles, trash and other waste — as boaters were reminded in 2013 when the July 4th weekend brought a rash of reports of E. coli infections near the island.

Authorities are also targeting underage drinking, dispatching more undercover officers in unmarked boats. Lt. Kent Vnuk, of the Hennepin County Sheriff’s Office Water Patrol Unit, said the youngest underage drinker cited last year was 14 and had a blood alcohol level of 0.18; deputies also cited a 17-year-old with a 0.30 blood alcohol content.

Stings this season have netted 34 citations for underage drinking in two weekends, up from a typical 15 citations over an entire summer. On social media, boaters have begun spreading the word: Officers are out and cracking down.

“It’s a day and night difference,” said Gabriel Jabbour, a marina owner who serves on the conservation district’s board. “This year, from day one and hour one, they’re out making sure you can have a good time without having chaos like before.”

In 2000, to help officers navigate congested Cruiser’s Cove next to Big Island, the conservation district installed lanes to restrict anchoring in certain areas. In 2003, more buoys were added and lanes were modified after boaters on the July 4th holiday refused to move for medics trying to reach an intoxicated man who fell in the water and later died.

This summer, authorities extended the lanes again and added color-coded signs so boaters can direct emergency crews in the cove.

For all its boating traffic, Lake Minnetonka is relatively safe, with fatalities falling to the single digits over the years; so far this year, just one person has died on the lake. Intoxication citations and accidents have also declined.

The Sheriff’s Office Water Patrol Unit was started in 1955, after 18 people died on Lake Minnetonka. Now it’s the biggest and busiest water patrol in Minnesota, patrolling a total of 107 lakes and rivers.

Deputies work shifts of 12 hours or more to cover their areas — writing citations, educating boaters, responding to emergencies and recovering the bodies of children and adults who drown.

“We’re responsible for everything bigger than a bathtub,” Vnuk said. “There’s not a harder job in law enforcement than water patrol.”

As Vnuk steered a boat across Spring Park Bay last week, white puffy clouds filled the bright blue sky and the sun glistened across the water. It was a quintessential summer day on the lake. Yet the bays were nearly empty — a rare calm moment before up to 9,000 boats swarm the lake for the long weekend.

This time, so will the officers.

“You’ll just see more of us,” Vnuk said as his crew prepped equipment. “It’s New Year’s, Fourth of July and Christmas all in one.”