Researchers at Oklahoma State say the eastern red cedar is not just a fire hazard and an allergy problem, but it's also drinking up Oklahoma's water supply. They are right in the middle of a study that is revealing more about how thirsty these trees really are.

Oklahoma's water supply is a big deal, and fights over water rights have gone all the way to the Supreme Court. Skiatook Lake is several feet below normal, and has been this way for years because of the drought.

Researchers are studying one tree in particular that is making the water even more scarce.

The eastern red cedar kind of looks like a short, stocky Christmas tree. You've probably heard of it because of the notorious wildfire risk it poses - or its pollen and resulting allergies.

But Rodney Will, a professor at Oklahoma State University and part of a team that's been studying the tree for years, say it's really thirsty.

"People don't recognize or realize how much water red cedar uses compared to native grassland, and that's what we're studying out here with this research," Will said.

Here's what they've found out so far.

First, this tree takes up about 20 percent of all the acreage in Oklahoma. The average grass prairie lets about 15 percent of the rain pass through the land - into streams and reservoirs - which turns into our drinking water.

That's called water yield. Researchers say water yield for red cedar is only 2 to 5 percent.

"That has pretty big implications for water yield and for human consumption of water in Oklahoma," said Professor Rodney Will, OSU.

In optimal conditions, Will and the team have found a single red cedar can drink up to 40 gallons of water per day. And if they totally cover a plot of land, they can take virtually every drop of rain water in a given year.

One of the OSU scientists on this team, Elaine Stebler, is trying to doing something about it. She's cleared 50 acres of red cedar from her land.

"I wanted to do something to be able to regain the value of that land," Stebler said. "Because, basically, the cedars just took away that value."

She has seen some regrowth, but she says before, the red cedars were so thick, she couldn't walk through them. And she noticed a drop in her water supply.

"Until we start reducing the number of cedars all across the state, one landowner isn't going to make a difference. But if we get a large reduction, we can stop this exponential growth," Stebler said.

Stebler, along with other red cedar removal advocates, believe controlled burning could be the most effective way to remove them. But doing that between burn bans and red flags warnings, could present its own problems.

Rodney Will says they are also looking at how badly the red cedar can damage the soil, and the best ways land owners can revive the soil.