The heavy rain last week, combined with an "unusually high" number of ducks and geese on the beaches, has forced Minneapolis to temporarily close two of its beaches to swimmers.

The Minneapolis Park and Recreation Board (MPRB) said Tuesday it has temporarily closed Lake Hiawatha Beach and Lake Harriet Southeast Beach after testing for E. coli bacteria found levels that exceeded state guidelines. 

No illnesses have been reported from swimmers at either beach, MPRB notes. It will retest the beaches on July 13, and the beaches will reopen when bacteria levels are within state guidelines.

All the other beaches in Minneapolis are open. 

What causes beaches to close?

Heavy rains, like the area experienced last week, can wash contaminants from the land into the water. These contaminants can be harmful to humans and pets if the levels of dangerous bacteria, like E. coli, get too high. 

According to the Minnesota Pollution Control Agency (MPCA), high bacteria levels in the state's waterways are most often caused by urban stormwater, failing septic systems, wastewater treatment plant releases and livestock. 

Waste from pets and wildlife (like an abundance of ducks and geese hanging out at a beach and relieving themselves) can also cause bacteria levels to rise, the MPCA said.

The MPRB and other agencies regularly sample bacteria levels at beaches and will proactively close them when bacteria levels are too high. This can help prevent people from getting sick from a waterborne illness. 

The most common symptoms of waterborne illness are vomiting and diarrhea, while other symptoms can include skin, ear, respiratory, neurological or eye problems, the Minnesota Department of Health (MDH) says.

The best way to prevent getting sick while swimming or playing in lakes and rivers is to avoid swallowing the water, showering before and after swimming, avoiding swimming after it rains and avoiding the water if you see a blue-green algal bloom, MDH notes.

Water quality at other beaches in MN

While the MPRB checks water quality at beaches in Minneapolis, other beaches may be monitored by their respective city, county or park authority (however, not all public beaches in the state are regularly tested for bacteria levels). 

In Hennepin County, the county monitors more than 30 beaches and lists the status of the beach on its website here. As of Tuesday afternoon, no other beaches in Hennepin County were listed as being closed due to higher-than-recommended bacteria levels.

There is also a beach monitoring program for Minnesota's beaches along Lake Superior. That's available here. As of Tuesday afternoon, a handful of beaches along the North Shore were closed due to high levels of E. coli, including the beaches at Agate Bay, Temperance River State Park and Grand Marais Campground.