At the Moody Street Dam in Waltham, Julie Wood, director of projects for the Charles River Watershed Association, notes the sun shining on the kayakers and geese enjoying the Charles River.
"Looking at the river here, you would not guess that there’s any problems," she said.
That’s because the problems are over on the other side of the Moody Street Dam, where there’s so little water it barely covers a bicycle rusting on the river floor.
“You do find some interesting things when the levels get this low," Wood said.
Riverbeds around the state—including the Charles River—are at historic lows as the region faces its worst drought in memory, raising questions about how a river like the Charles, full of old dams, is managed.
When we’re not in a drought, the water often pours over the Moody Street Dam—one of 20 dams on this 80-mile river. But now, water is just dribbling through several wooden boards on top of the stone dam.
“Essentially what we have when flows are so low and we still have all of these dams in place, is instead of a healthy flowing river system, we get sort of a series of lakes," Wood said.
And with that, Wood said, come some of the environmental challenges of a lake. For one thing, the water is still and evaporating.
“The water that remains in the river is heating up, and certain wildlife species are very sensitive to temperatures," she said.
Also, as that water evaporates, pollutants in the river can become more concentrated.
“One issue we have on the Charles that’s very significant is blue-green algae, or cyanobacteria, and those low-flow warm water conditions are really rife for cyanobacteria blooms," Wood said. That's something toxic that usually happens in lakes.
“You could look at it as a series of lakes," said William Gode, director of flood control management for the state Department of Conservation and Recreation. “I have more frequently likened it to a series of champagne glasses at a wedding, where the water is going into the top champagne glass, and once that champagne glass overflows, it fills the ones below it."
Gode said fixing some of the problems caused by the Charles’ individual lakes, or champagne glasses, or whatever, is more complicated than just blowing up all the dams. “You wouldn’t have quite so many champagne glasses, and the water would get to that last champagne glass more quickly," he said. "And it’s possible that that champagne glass would fill up faster than it could be drained out."
That last champagne glass is the Charles River Basin, and it’s Gode’s job to keep Boston and Cambridge from flooding. The basin wants to be tidal. It used to go up and down by as much as 12 feet. Now, Gode controls the flow to keep it within a two-foot range.
“Additionally, it allows us not to have that seashore smell that you have at low tide twice a day, in the heart of the city," he said.
Back upstream in Waltham, Gode has to make sure there’s enough water on the other side of the dam for all the kayaks and canoes. He says even if they were to remove the boards at the top of the Moody Street Dam, it still wouldn’t help downstream, because the big faucet in the sky is turned off.
“The way I look at it is, you got a bathtub," he said. “If you pull the stopper out of the bathtub, you’re going to have a very large flow through the drain, for several minutes.”
And then you’re back to an empty tub again.
“There’s only so much water," Gode said. "We obviously have a drought, and we cannot make water. We have to manipulate the water we’ve got and try to balance the needs of recreation, of flood control, of fish, the general environment, and it’s a balancing act.”
Until that big faucet in the sky starts again, that balancing act is going to be harder to pull off.
