Flood concerns along the San Joaquin River between the Stanislaus River and Lathrop will not end when the storms end.

That’s because the snowpack on the Tuolumne and Stanislaus watersheds — the two rivers that play the biggest role in pushing water through the tourniquet that is the San Joaquin River between the Airport Way bridge and where it splits into the Old River and new channel just past the Mossdale Crossing — is at 275 percent of normal.

And because the snowpack  is at 275 percent  of normal in early spring, warmer weather — particularly if it is higher than normal for April and even May — could create a significantly above average runoff.

High spring runoffs mean the upper portions of levees that are higher up and virtually dry all year round will be saturated with water and put to the test.

It is why San Joaquin County emergency officials have warned flood concerns tied into the integrity of levees will be a concern for weeks, if not, months to come.

There are currently numerous boils being addressed in River Junction — the 5,000-acre reclamation district 10 miles south of Manteca where the Stanislaus and San Joaquín rivers meet.

There are a number of boils directly behind the Durham Ferry School operated by the San Joaquin County Office of Education off of Airport Way.

Boils can be a precursor to a levee failure if efforts to sandbag and shore the area around them up isn’t successful.

In 1997, boils triggered levee breaks in 11 different areas along the river south of Manteca. That led to 70 square miles between Manteca and Tracy being flooded.

Councilman Charlie Halford on Tuesday reminded staff they need to be prepared as the levee situation could be precarious for the next month or so.

Should the levees fail south of Manteca there is a cross or dry levee that will protect the southwest part of the city.

Back in 1997, that levee held back water for several weeks until the threat passed.

At the time, there were no homes in the area. Now there are close to 1,000 homes as far east as Woodward Avenue and Airport Way should that dry levee fail.

It has yet to warm up to typical mid-March temperatures.

And the National Weather Service expects it to stay that way into early next week after yet more showers are expected on Monday in the Northern San Joaquin Valley.

Abnormally cool temperatures are good as it means the snowpack when it starts to melt in earnest will do so at a pace that is controllable through timed reservoir release.

On Tuesday, there were 19 people being sheltered in the emergency evacuation center at the Manteca Senior Center. The evacuees are from Airport Court south of Manteca and Haven Acres north of Lathrop. Both rural neighborhoods are on the river side of San Joaquin River levees.

Manteca Fire Department’s water rescue team has been called upon on a regular basis to assist with flooding issues. The latest was a rescue call for goats stranded on an island the higher flowing Stanislaus River had created.

The Airport Way bridge was still at flood stage Tuesday night at 9:45 p.m., with the gauge reading 29.3 feet.

That prompted Halford at Tuesday’s council meeting to note that “old timers use to say (the levees) can hold 29 days at 29 feet.”

Halford stressed that as conditions develop, that may not be true this year.

“We need to be ready in case,” Halford advised city staff.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com