Water quality in the Thames River is improving, despite recent reports of high E. coli levels by an area angling group, says the Upper Thames River Conservation Authority.

Trout Unlimited took water samples from the river's Springbank Dam reservoir last year that registered coliform readings as high as 55 times the maximum allowed for swimming.

Published in Better Farming magazine last October, the findings are raising questions about the safety of the river reservoir for recreation.

A spokesperson for Trout Unlimited could not be reached for comment.

But the results came as no surprise to authority officials or the Middlesex-London Health Unit that have monitored the river's water quality for decades.

"That (testing results) is certainly way higher than what we normally see and I suspect it's a one-off sample," said Ian Wilcox, the authority's general manager.

"Generally, the water quality is better than it was 30 years ago and over the last 20 years we've seen a steady decline of bacteria."

Wilcox said authority tests have shown coliform spikes in excess of 5,500 colony-forming units (CFU) per 100 millilitres of water, the maximum allowed for public beaches.

However, the average is about 375 units. In the late 1990s, the average was more than 900 CFUs.

"There's still room for improvement, but people need to understand it is getting better because people across the region have been working on this for decades," Wilcox said.

E. coli comes from a number of sources on the river. A major contributor is the city's Greenway Pollution Control Plant.

Bacterial spikes are common during periods of heavy rain when millions of litres of partially treated sewage overflow into the river, mostly due to cross- connected storm and sewage lines the city has been replacing in recent years.

Other sources include the municipalities of Stratford, Woodstock, Ingersoll and Mitchell, farming and faulty septic systems over 3,500 square kilometres.

The Thames River doesn't have public beaches so the Middlesex-London Health Unit doesn't monitor it as closely.

"(The E. coli) is something we've known about for some time," said Jim Reffle, the health unit's director of environmental health.

"It's not recommended the river be used for drinking water or swimming."

The only local beach in London is at Fanshawe Conservation Area. The beach is screened in and the water treated with ultraviolet light that kills bacteria.

Trout Unlimited and other angling and commercial fisher groups have been at odds with the city in recent years over the reconstruction of Springbank Dam.

The groups first wanted a fish ladder installed at a cost estimated at $1 million, then later called for the dam to be removed and the river restored to its natural state.

There are many fish species in the river, including pickerel, smallmouth bass, pike, yellow perch and even trout.

Populations of most fish species are small, especially in the city, mostly because of poor water quality that affects spawning.

The dam was built in the late 1800s mostly for recreational use but later to assist in flood control.

It is now being rebuilt at a cost of $6.7 million with new hydraulic steel gates that will make it easier for the city to maintain after flooding damaged the old structure in the summer of 2000.

"Actually, this rebuild will make the dam far more environmentally friendly," Wilcox said.

"It can be opened and closed much more quickly to meet fish migration demands and you can open it slightly to skim off algae."