Human activity is changing the water quality of most of bodies of water globally.

Researchers looked at trends in "97 streams and rivers from Florida to New Hampshire," a Cary Institute press release reported.

They found that a dramatic two-thirds of the various bodies of water had become significantly more alkaline over the past 25 to 60 years.

 "What we are seeing may be a legacy effect of more than five decades of pollution. These systems haven't recovered. Lagging effects of river alkalinization are showing up across a major region of the U.S. How many decades will it persist? We really don't know the answer," Lead author Sujay Kaushal, an associate professor and aquatic ecologist at the University of Maryland, said.

Alkalinity is a measurement of how well the water neutralizes invading acid. A higher alkalinity can lead to toxic ammonia and algae blooms, which are a big threat to wildlife. Elevated alkaline levels  can also cause pipe scaling, and " exacerbates the salinization of fresh water."

Acid rain and agricultural runoff are mostly to blame for this phenomenon, the harsh substances eat away at limestone and even cement, which "infects" the water with alkaline particles.

Some of the rivers found to have a higher alkalinity exist around "Washington, D.C., Philadelphia, Baltimore, Atlanta, and other major cities." This is due to higher instances of acid rain and a larger area of cement coverage.

Sources that flow into the Chesapeake Bay, and other rivers that have a significant algae infestation, are also affected. Appalachian Mountain streams have seen a significant increase in alkalization because the sloping ground surrounding them encourages sediment to run into the water.

"This is another example of the widespread impact humans are having on natural systems. Policymakers and the public think that the acid rain problem has gone away, but it has not," ecologist Gene Likens, Founding Director of the Cary Institute of Ecosystem Studies, a co-discoverer of acid rain, and a co-author of the study, said.

"Acid rain has led to increased outputs of alkalinity from watersheds and contributed to long-term, increasing trends in our rivers. And this is twenty years after federal regulations were enacted to reduce the airborne pollutants that cause acid rain," Likens said.