He said he believes LeGardeur may be expecting too much of the city.
"I don't begrudge his efforts to make it better for fishermen," Gracie added, "but I don't think he's going to get too much."
Howells said the city coordinates with the state Department of Natural Resources to safeguard the trout, especially to ensure that water temperatures don't get too high. When the stream gage downstream from the dam shows the water temperature rising, cooler water is released from beneath the reservoir's surface to offset the warmer water spilling over the dam, he said.
However, it's not easy for the city to anticipate rainstorms, Howells said, and lower the reservoir level quickly enough to offset water pouring into the watershed. Besides, he added, drawing down the reservoir undermines the reason the dam exists.
"We're trying to retain the maximum amount of storage for public water supply," Howells said, "so spillover for us isn't necessarily a problem."
But LeGardeur called that "short-sighted." He pointed out that New Jersey officials ordered water levels in four drinking water reservoirs in that state drawn down in an attempt to mitigate predicted severe flooding as superstorm Sandy swept up the coast in October 2012.
Besides potentially affecting the Gunpowder's trout and recreation, LeGardeur said high flows are washing extra sediment into the Loch Raven Reservoir, reducing its capacity to hold water. The erosion also brings phosphorus, a plant nutrient that feeds algae blooms and affects water quality.
The high flows have eroded the banks and washed out some of the fallen tree limbs and other debris that give trout places to hide, said Mark Staley, central region fisheries manager for the state Department of Natural Resources. But the fish do not seem affected by the flows, or temperature fluctuations, he said.
The number of brown trout estimated in the stretch immediately downstream from the dam in an annual fall survey has "tailed off some" in recent years, Staley said. The number of young fish seen there last fall also was down from past years, he said.
But the river's trout population as a whole still appears healthy, well above historic lows, Staley said. Moreover, a visual survey this spring found abundant newly hatched fish, called "fry," in the water — though that was before deluges flooded the river in April.
"Overall we haven't seen impacts due to the way they're managing the reservoirs," Staley concluded. "The water's cold, it's clear. You've got tons of brown trout publicly accessible for nine miles. Where else do we have something like this?"
Charles Gougeon, DNR's inland fisheries program manager, said that while it seemed Howells' predecessor did adjust the reservoir level at times in advance of predicted storms, he stressed that the city now is "following protocols" and has worked with the state to maintain the fishery.
Still, Gougeon did not rule out considering changes to adjust for altered natural conditions.
"There's always room for improvement," he said. "The more we learn and the more checks and balances we have, the better."