Changes to a 130-year-old law included in the federal budget could have a negative impact on how Canadians can navigate through the nation's rivers and streams in the future, critics charge.

"People don't know what's going to happen to not only their favourite bodies of water but bodies of water that they know are important to the ecology of the area," said Jay Morrison of the Canadian Parks and Wilderness Society.

The Navigable Waters Protection Act, passed when lakes and rivers were the main transportation routes, used to say any water deep enough to float a canoe must have an environmental assessment before a project starts.

But the federal transport minister can now decide what waterway qualifies as major or minor under the legislation and if there needs to be any environmental assessment before development goes ahead.

The government argues that that the old law treated small creeks and big rivers the same and was slowing down crucial construction projects.

Transport Minister John Baird said that no one wants to harm the environment. But he said some of the rules predate Confederation and were getting in the way of the government's infrastructure package.

"It is essential if we want to get shovels in the ground. There's a reason why it hasn't been going as quickly as many of us would like and this is one of the reasons," he said.

But the changes have sparked a wide coalition of paddlers, environmentalists and hunters and anglers who fear that a dam or a bridge could be built on their favourite river with no public input.

"The ability of Canadians to use the waterways for recreational purposes is something that millions of Canadians not only take advantage of but hold very dear," said Greg Farrant of the Ontario Federation of Anglers and Hunters.

Thousands have been reportedly emailing politicians over the changes.

Liberal Senator Joseph Day, who chairs the Senate Finance Committee, said he has received more than 8,000 messages on the topic.

"The canoeists, the outdoors people, the people that are involved in guiding people in the summertime, and then you'll hear from a certain industry, fishermen — so it's a wide cross section.

Farrant said that no one wants to stop job creation during this economic recession but people want it done without damaging the environment at the same time.

"We all understand that but at the same time we don’t want to throw the baby out with the bathwater."