Where does the muck come from? Mostly York and Lancaster

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· What do you think about the sediment stacking up at Conowingo and in the Chesapeake Bay? Talk about it on The Exchange, our community message board.

Where does the sediment trapped behind the dams on the Lower Susquehanna River come from?

Everywhere.

Your yard. The farm field behind your house. The sleepy former mill stream down the road. The construction site of the new shopping center out on the highway. The quarry next to the river. It's what environmental regulators call a "nonpoint source."

It flows into the tributaries that twine through our community and courses into the river after a pouring rain or snow melt.

After a heavy morning storm passed through the area Aug. 2, plumes of Yoohoo-colored water poured into the Susquehanna.

Liz Winand, of Shank's Mare Outfitters near Long Level, says runoff is a constant problem, but strong storms dramatically illustrate the issue. Her business, which rents kayaks and runs water tours, sits at the mouth of a stream she says is particularly susceptible to runoff, Bull Run. "After a storm, you can see all the mud just running into the river," she says.

Bull Run is a narrow stream worming its way down a heavily developed river hill, with houses hugging the banks. The creek emerges through a culvert and dribbles into the river on a dry day. But it gushes after a summer storm.

Winand says development causes the runoff. "There are no buffers to prevent erosion."

Winand's son, Devin, offers a kayak tour that shows the contrasts between Bull Run, a creek susceptible to runoff, and a "healthy" waterway just south of Bull Run -- Fishing Creek.

The difference is dramatic. At the mouth of Fishing Creek, you glide under a bridge and enter a natural cathedral of trees towering above -- a shady cove with vegetation-covered banks that help hold the soil in place and prevent erosion.

It's cool and quiet as Devin Winand paddles a few hundred yards to a rocky section that's no longer navigable.

"Of all the creeks on this section of the river, this one is the cleanest because there's no development," he says.

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But development isn't the only culprit. Farming is also a major contributor, particularly farming operations that don't follow modern best land management practices: Plowing on contours, strip

cropping, no-till farming, stormwater management.

These are issues Gary Peacock, watershed specialist with the York County Conservation District, has been working for years to improve.

He's on the front lines of the watershed management efforts that many regulatory agencies cite as the foremost approach to dealing with river sediment.

"A big part of my program is education," he says, meaning he tries to help private land owners stop erosion. Peacock and the conservation district also get involved in stream restoration projects, fixing eroded banks, planting appropriate vegetation, assuring proper buffer zones between creeks and nearby development, and keeping livestock out of streams with fencing.

Peacock is encouraged that his efforts are having a positive effect, noting continuous decreases in sediment loads.

Cathy Curran Myers of the Pennsylvania Department of Environmental Protection agrees the sediment load from the state has decreased in recent years, and the state hopes to escalate those improvements. That, she says, should be the main focus of the sediment issue, rather than studying reservoir dredging or other dramatic remediation efforts.

Last year, Pennsylvania's sediment load to the bay was 1.06 million tons, a reduction of 460,000 tons from the baseline of 1.52 million tons in 1985. DEP officials note the state is 88 percent of the way to its current goal for sediment reduction under the Chesapeake Bay Program.

* * *

A newly discovered source of river muck is legacy sediment associated with old mill dams, a phenomenon described by Franklin & Marshall College professors Dorothy Merritts and Robert Walter.

During colonial times, literally thousands of mills dotted the river basin countryside, creating slackwater ponds where sediment would settle and accumulate.

Over the years, many of the dams were removed or breached, and the waterways began to cut new streambeds through the sediment, carrying much of it downstream and into the river.

These streams now have steep banks that are susceptible to erosion, and conservation officials have been working to target the biggest problems areas for restoration projects.

* * *

One of the worst offenders for sediment loading in the lower Susquehanna is the Conestoga River watershed in Lancaster County, says Dan Bierly, of the U.S. Army Corps of Engineers.

"That's because it's heavily farmed, with maybe not the most modern methods," Bierly says, noting that many farmers fail to leave adequate buffer zones between plowed areas and the water.

* * *

Drive down River Road to the mouth of the Conestoga, just below Safe Harbor Dam, and it's easy to see how farming is a factor. Pass the paint-peeled riverside shacks south of Columbia and you enter stunningly beautiful farm country.

At the park surrounding the mouth of the Conestoga, you can see the evidence of farmland erosion.

Mikey Crespo, 10, and Olivia Johnson, 6, of Conestoga, Lancaster County, sit on a sand bar in the river on a lawn chair and an inner tube, fishing during a family outing. Nearby, an inlet into the river is covered with sediment, which Mikey picks up in big, gushy handfuls.

* * *

While there are similar problems on the York County side of the river -- at Bull Run, for instance -- Peacock takes some pride in studies that show the sediment erosion problem is worse in Lancaster County than York County.

That suggests York County is doing something right.

But Pennsylvania environmental activists say that doesn't mean sediment is "not our problem."

It's an ongoing problem for the bay that will only get worse as the basin behind the Conowingo dam fills to capacity, which is likely to happen in 15 to 20 years.

That means it's a regional problem.

Most of the sediment comes from Pennsylvania, the larger part from the southern reaches of the Susquehanna -- and an outsized portion comes from Lancaster and York counties. And we're all Pennsylvanians.

Lower Susquehanna Riverkeeper Michael Helfrich and others say Pennsylvania must contribute to efforts to deal with the sediment issue -- encouraging state and federal representatives to move more aggressively, both in requiring stronger land use rules and at least seriously studying whether the muck behind the dam can be dredged and turned into a useful material.

Your opinion

· What do you think about the sediment stacking up at Conowingo and in the Chesapeake Bay? Talk about it on The Exchange, our community message board.

Also of interest

- How to remember what dam is where on the Susquehanna River. Read more at York Town Square.