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High flows on Gunpowder stir debate

Floods and FloodingConservationNatural ResourcesWeather ReportsFishingAquaculture

Tucked amid the woods of northern Baltimore County is one of Maryland's natural gems — the Big Gunpowder Falls, a nationally renowned trout stream that draws anglers from far and wide to try their skills and luck in the cold, rushing water.

But some fishermen and fishing guides say they're having a harder time getting at this prized outdoor resource — though it's publicly accessible in Gunpowder Falls State Park — because of unusually heavy river flows that make it hard to fish or even stand at times in the water. They contend the management of Prettyboy Reservoir on the upper Gunpowder by the city of Baltimore is a factor, and they worry that the sensitive trout also may be suffering.

"Over the past three years of flooding, we've seen a dramatic loss of healthy banks, a riverwide decrease in the population of trout and less woody debris" where the fish can find shelter, said Theaux LeGardeur, the Gunpowder Riverkeeper. Besides his nonprofit environmental advocacy for the river, LeGardeur runs a fly-fishing business in Monkton.

The reservoir is one of three developed by the city early in the last century to supply drinking water to about 2 million residents in the metropolitan area. The 130-foot high Prettyboy Dam was built in 1932. City officials acknowledge there's been a lot of water spilling over it of late, but they say that's because of unusually heavy rains.

"I'm sure that you can find areas of erosion," said Clark Howells, watershed section manager for the city Department of Public Works. But he said the river's flow has been elevated by above-average rainfall, and there's little the city can do about that because the reservoir is kept as full as possible to ensure maximum storage of water for the region's residents.

"These reservoirs are managed for public drinking water supply," Howells said. "They're not managed for flood control."

The eight-mile stretch of river below the dam is what's known to anglers as a "tailwater" fishery, because the Gunpowder's flow is dependent on water from Prettyboy Reservoir.

Many, including LeGardeur, credit the city's management of the dam for making it possible in the first place for brown trout to thrive and reproduce in the upper Gunpowder the past 30 years without the need to restock with hatchery-reared fish, as so many other streams are.

The watershed agreement the city struck at Prettyboy, after years of urging from the Maryland chapter of Trout Unlimited, guarantees a water flow through the dam of at least 11.5 cubic feet per second, even in dry times.

LeGardeur and some others say what they worry about now is too much water spilling over the dam, making it more difficult and even unsafe at times to wade into the river to fly-fish. Flows have consistently been well above average, and on a couple occasions this spring after deluges soared to 1,000 cubic feet per second, flooding the valley.

Rainfall has been more than 7 inches above normal to date this year at Baltimore-Washington International Thurgood Marshall Airport, and even higher in other parts of the state.

But LeGardeur said he believes the weather-driven surges could be mitigated if the city would lower the level of the lake behind the dam a bit to hold the runoff from at least modest amounts of rain falling on the 80-square-mile watershed that drains into the reservoir.

"I used to tell people coming up from Washington to wait if we'd had 2 or 3 inches of rain," LeGardeur said. "Now, if we have a half-inch, I tell them to wait four or five days."

Fred Churchill, a 72-year-old angler from Vienna, Va., said he was nearly swept off his feet one day in April by strong currents when he tried wading to a favorite fishing spot. He acknowledged that he'd been so eager to take advantage of the first warm spring day that he didn't check online to get real-time flow readings from a stream gage maintained by the U.S. Geological Survey. He made it to his destination without falling, he said, but left shortly afterward because it was just too difficult to fish.

An added concern comes in spring and summer, LeGardeur said, when warmer water spilling over the dam from the surface of the reservoir heats up the river. Trout do best in cold water and become stressed when water temperatures rise into the high 60s and 70s.

Jeff Lewatowski, a fishing guide from Churchville who works out of LeGardeur's shop, said he also believes the reservoir may be a factor in changing river conditions.

"When that reservoir's that full, even if we get a minor rainstorm, we get spillover," Lewatowski said.

The fish seem to behave differently during the surges, he said, and he's noticed that natural cycles of mayfly hatches — a prime fish food and lure used by anglers — have been disrupted at times.

Not all anglers share the concerns.

"The city's done a reasonably good job of managing the fishery," said Jim Gracie, a longtime Trout Unlimited member who recalled spending 17 years nurturing and stocking trout on the Gunpowder to build the population to the point where it could sustain itself.

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."

tim.wheeler@baltsun.com

Copyright © 2014, The Baltimore Sun
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