The Potomac River’s already poor water quality deteriorated over the past five years, according to an environmental report released Thursday.

The Potomac Conservancy gave the river a “D” grade in its “State of the Nation’s River” report, down from its 2007 rating of “D+,” citing a population that swelled 5 percent to reach six million along with poor land use practices. Researchers also discovered an increased amount of contaminants, affecting the Potomac’s fish population.

Environmentalists have discovered intersex fish in the waterway – or male bass fish that have female characteristics, like underdeveloped eggs.

“There has to be an awareness of the importance of water,” Potomac Conservancy spokeswoman Anne Sundermann said. “People need to realize that water does have a value. As the population grows, this becomes increasingly obvious.”

She said the river picks up pollutants as it heads down stream, a result of runoff from rainfall that gets contaminated, as well as from deforestation in the city.

About 90 percent of the District’s drinking water comes from the Potomac, as it is treated according to Environmental Protection Agency standards before it reaches the public.

But the river is unsafe for fishing or swimming, Sundermann said.

The Potomac faces pollutants that she calls “non-point sources,” or causes of contamination that are difficult to single out and harder to control, ranging from lawn fertilizers to oils on roads that flow into the river.

“Scientists have documented the presence of hundreds of compounds, including dozens of pesticides, pharmaceuticals and even the residues of illegal drugs [in the Potomac River],” the report said. “These chemicals can originate from everyday products like shampoo, perfumes, prescription drugs and birth control pills, and from farm chemicals and animal manure.”

The report offers some solution plans for the long list of pollutant-causing problems, including better storm water management and greener building practices.