Many central Oklahomans have come to know this lake by a filthy nickname.

North of State Highway 9 in northeast Norman is Lake Thunderbird, or as many call it, “Dirty Bird.” The lake is a man-made reservoir used primarily for drinking water for the cities of Norman, Midwest City and Del City, but is also a popular spot for swimming, fishing and boating.

But is its nickname indicative merely of its appearance, or something more? Here’s what you should know.

Why is Lake Thunderbird called ‘Dirty Bird’?

The “Dirty Bird” moniker was most likely given to the lake because of the red, murky appearance of its waters, especially near the shore.

Robby Short, spokesperson for the Oklahoma Water Resources Board, said this is due to the red soil the lake was built on top of.

“If you’re from central Oklahoma, you’re probably familiar with red dirt,” Short said. “I don’t know why the color of the lake would be so surprising. I think it’s pretty much the color of any pond in the area as well.”

Is Lake Thunderbird actually dirtier than other lakes?

While the nickname may scare some people off from participating in recreational activities at the lake — or make others hesitant to drink the water it provides — Short said there’s nothing to worry about.

“The (nickname) and the color of the water is based on the soil,” Short said. “There’s no danger in that, unless you go swimming in white clothing, there’s the danger it might get stained.”

Because the lake provides public drinking water, it is part of the state’s Beneficial Use Monitoring Program. The most recent report came out in 2021 and found that complaints to the City of Norman’s drinking water facility about the water’s taste and odor went down slightly.

Any taste and odor complaints are typically based on the water’s treatment, and can be “a result of excess nitrogen or phosphorus in the water being removed during the treatment process,” Short said. These complaints also typically align with when Lake Thunderbird turns over, the report said.

The report also found that levels of chlorophyll a, a measure of the amount of algae growing in a waterbody, were at their highest annual average in the past decade.

The lake is not supposed to exceed a long-term average chlorophyll concentration of 10 micrograms per liter at a depth of 0.5 meters. The average in 2021 was 33.45 micrograms per liter, and then ten-year lake-wide average was 27.80, with 84% of samples higher than 10 micrograms per liter.

The report found that because of these levels, the lake’s status as a private and public water supply is impaired — however, Short said while not optimal, the levels are still safe for public use.

Are some Oklahoma lakes cleaner to swim in than others?

Short said the state doesn’t necessarily have a way to rank what lakes are the “cleanest.”

However, some lakes may be more prone to strong currents after heavy rainfall or areas that could become stagnant, Short said.

Overall, Lake Thunderbird is a safe body of water to cool off for the summer. However, we understand if you’d rather find a lake whose waters won’t stain the inside of your swimwear.

This article originally appeared on Oklahoman: Is Lake Thunderbird, AKA ‘Dirty Bird,’ any dirtier than other lakes?