Any attempt to dam the large Adelaide River in the Northern Territory would be doomed to fail and would be blockaded by protesters, an environment group says.

The director of the NT Environment Centre, Stuart Blanch, reacted Saturday to news the Federal Government may be prioritising a proposed project to dam the Adelaide River.

The Northern Territory has been looking for ways to increase Darwin's water supply, which faces shortages in coming years.

The proposed Warrai dam, which has been talked about since the late 1970s, would be built about 120 kilometres south of Darwin.

Building the dam is among the priorities of Agriculture Minister Barnaby Joyce, and the only Top End project on a list of urgent dam priorities apart from the expansion of the Ord irrigation project.

"We would certainly oppose it and blockade it," Dr Blanch said.

He added that the proposed dam would not only fail to store water because of the high evaporation rates and the shallow design, but any water produced would likely be too expensive for farmers to use.

And even if farmers could afford the water, he said, the poor soil quality in the area made agriculture unlikely.

A dam could also cause flooding in nearby Litchfield National Park, and would likely be opposed by Aboriginal groups, he said.

"Dams kill rivers. It is like getting a blood clot in your leg," said Dr Blanch, whose doctoral thesis covered the ecology of the Murray River.

Warrai dam would impact on burial grounds: elder

Last month, Aboriginal elders from the Kamu people were critical of any plans to dam the Adelaide River.

One of them, Margie Foster, said there were significant sacred sites in the area.

"We have dead people all over this land and we are here to look after this land," Ms Foster said.

Another elder, Maxine Storer, said the Kamu would petition the government if it went ahead with plans to dam the Adelaide River.

"It's not only us being the traditional owners for this area that it will have an impact on - the tourists I suppose," Ms Storer said.