Water quality problems at Pennsylvania's popular Lake Erie beaches in Presque Isle State Park have increased because of more and bigger storms this summer after showing marked improvement a year ago.

According to the Natural Resource Defense Council's 18th annual beach water quality report, released yesterday, swimming prohibitions or advisories were issued on only six days last year, a dramatic improvement from the 53 days those health warnings were issued in 2006 and 39 days in 2005.

But this summer the swimming prohibitions or advisories already have been issued on one or more of Presque Isle's 13 beaches on seven different days, and that's before the start of August, when most of the health warnings were issued in previous years.

As in previous years, the report said all of the swimming prohibitions and advisories were caused by elevated E. coli bacteria levels due to storm water runoff into tributary streams that carried untreated waste from wild and domestic animals, pets and humans into the lake.

"We've had more advisories and almost all are related to rain events, particularly flash heavy rain events," said Harry Leslie, the state park's operations manager. "Historically it's been like that. Last year was just drier."

In addition, large floating mats of Cladophora, a type of green algae found in the Great Lakes, have been identified as a source and transport medium for the bacteria.

The latest water health alert on Erie beaches was issued Thursday for Beach 1 West Extension, Beach 1, Beach 1 West and Beach 6. Barracks Beach was added to the swimming advisory on Friday. All advisories were lifted Sunday.

There were no swimming restrictions caused by high bacteria counts in effect on the park's seven miles of sandy beaches yesterday, according to the Presque Isle State Park office. Beaches 9 and 10 were closed for sand replacement and construction.

Beginning last year, the Erie County Health Department changed its water quality warning system. Instead of saying a beach was closed because of water quality concerns, high E. coli counts now trigger "swimming advisories" that warn beach goers of the risks and are posted at the affected beaches. Higher bacteria counts trigger "swimming restrictions" that prohibit swimming.

Andrew Glass, Erie County Health Department director, said the department, which does the beach water testing, has not found any new or increased source of the E. coli contamination this summer.

"There have been more this year but the bacteria counts fluctuate and depend on a number of factors from the number of storms to wind direction whipping it up from sediment," Mr. Glass said.

Nationally, based on data from the U.S. Environmental Protection Agency, the number of beach closings and advisories in 2007 topped 20,000 for the third consecutive year, indicating that swimmers' health continues to be at risk, the report says. The most advisories and closings nationally occurred in 2006.

"Some families can't enjoy their local beaches because they are polluted and kids are getting sick, largely because of human and animal waste in the water," said Nancy Stoner, director of the NRDC's clean water project.

Across the nation, 7 percent of beach water samples violated federal health standards for E. coli bacteria. In the Great Lakes, 15 percent of the samples violated those standards, the highest percentage of any region in the nation.

The NRDC report criticized beach water standards that are more than 20 years old and said they rely on outdated water sampling and testing methods that leave beach goers vulnerable to a range of illnesses. E. coli bacteria at elevated levels can indicate the presence of animal or human waste that could contain other pathogens, viruses or diseases.

The most common health problems related to pathogen exposure in recreational waters are respiratory illness; ear, nose and throat infections; gastroenteritis; dysentery; and hepatitis.

The NRDC also urged Congress to pass pending Beach Protection Act legislation that would provide money for water sampling and require use of faster testing methods that provide more timely information to beach users about whether the water is safe.