Suggested Trip

Still Waters Run Deep at Seneca Slackwater


Four islands and three creeks…that’s what I initially set out to see when I launched my kayak on the Potomac River at Algonkian Regional Park in Sterling, Loudoun County, Virginia.  But I saw much more: a plethora of interesting wildlife, many historic structures, scenic views, and clean, clear water.  At first, I was a little hesitant to go paddling in the early autumn after a drought, fearing that I might spend more time portaging than paddling.  But after studying maps, I noticed there was a dam just two miles downstream from the boat ramp forming an area called Seneca Slackwater which ensures enough water to kayak year-round.  

So, what’s the story behind Seneca Slackwater?  Completed in 1831, the 2500-foot-long Dam No. 2 was built to feed water into the Chesapeake and Ohio (C&O) Canal at Lock 23 (a.k.a. Violettes Lock), which raised and lowered boats so they could navigate along the canal.   The dam backed up water for nine miles, forming Seneca Lake, and although it suffered ice damage and had to be rebuilt twice, it operated until the late 1800s.  The rubble ruins that remain today create an area deep enough for water skiing on a good day.  Kayaking here, I saw no signs of cut rocks, concrete, or metal because – unlike most dams I’ve encountered – this one was made of brush and gravel.

Lock 23 (aka Violettes Lock)    

After weeks without rain, sediment had settled out of the water, affording me the rare chance to study the bottom of the Potomac River over five feet down!  I saw several turtles swimming alongside my boat, clams as large as my palm, a multitude of fish, and plenty of golf balls that never made it to the green at the nearby golf course.  Perhaps my most interesting underwater discovery was a freshwater sponge just west of Lock 23.  This filter feeder is often mistaken for algae but is, in fact, a collection of individual microscopic animal organisms working in unison.  Sponges are an indicator of clean, clear water and a healthy ecosystem, so they are always a welcome find.

Freshwater sponge near Lock 23    

Four islands emerge from the Slackwater: Selden, Van Deventer, Tenfoot, and Sharpshin.  Selden Island is private property, while Van Deventer Island is a public hunting area owned by the Maryland Department of Natural Resources (DNR) and home to wild turkeys.  Just downstream of Van Deventer Island is the privately owned Tenfoot Island where I saw numerous paw paw trees, but none bearing fruit – I’m guessing I was a little too late for that.  The last, smallest, and most downstream island I paddled by was Sharpshin Island, owned by  Potomac Conservancy.

Wild turkey at Van Deventer Island    

For kayakers who prefer narrow, wooded streams, there are Broad Run, Seneca Creek, and Sugarland Run.  The mildly scenic Broad Run lies on the Virginia side and empties into the Potomac River at Selden Island.  This shallow waterway lies 3.5 miles upstream from the launch site and 5.5 miles from Dam No. 2 where the effects of the Slackwater are hardly noticeable.

A better paddling choice is the picturesque Seneca Creek, which lies two miles downstream of the launch site on the Maryland side.  At its mouth is the Seneca Creek Aqueduct (a.k.a. Aqueduct No. 1) and Lock 24 (a.k.a. Riley’s Lock).  Both structures were constructed using Seneca Red Stone from the nearby Seneca Quarry, the same distinctive sandstone which was used to build the Smithsonian Castle on the Washington Mall.  The aqueduct, which dates back to 1832, permitted boats to cross Seneca Creek via a water-filled bridge, while Lock 24 moved boats to and from it.  I was able to paddle about 0.8 mile upstream on Seneca Creek through the 6300-acre Seneca Creek State Park before having to portage.

The last creek I explored was Sugarland Run, located in the Algonkian Nature Preserve, part of Algonkian Regional Park. This spot is a real gem due to its great scenery and easy access, residing just a half mile downstream of the launch site on the Virginia side.  Despite a couple minor portages, I was able to paddle upstream on it for about a mile until I encountered shallow riffles.

The north side of the Slackwater is bordered by both the 1475-acre McKee Beshers Wildlife Management Area and the Chesapeake & Ohio Canal National Historic Park. I saw many people out bicycling on the towpath, a 184.5-mile path that runs from Washington, DC to Cumberland, MD. The canal was built between 1828 and 1850 for mules to tow boats on the canal.  Nearby, egrets and great blue herons perched in the trees or on the shore until I approached.  One was so focused on devouring a large frog that it allowed me to get unusually close.

Great blue heron eating a frog    

Before returning to the Algonkian Regional Park boat launch, I paid one more visit to the Dam No. 2 rubble.  Climbing up onto a fallen log to get a better view, I saw some kayakers paddling south to a section of the Patowmack Canal to play in a whitewater section of the river.  Looking down from my log, I found several piles of animal dung containing paw paw seeds.  I was pleased to know that if I couldn’t sample this mango-banana-tasting fruit, at least it didn’t go to waste.

Standing near the most upstream part of the dam, I took some time to appreciate the shallow, rocky downstream sights on the Potomac juxtaposed with the clear, open-water upstream section that forms Seneca Slackwater.  The dam, streams, islands, wildlife, clear water, and historical sites all come together to make this a truly magical place to paddle.

For more information, see
Maryland Historical Trust – Violet’s [sic] Lock House, Lock and Dam #2 (Lock 23) 

River Explorer – Dam No. 2  

Maryland DNR – The Potomac River and the C&O Canal, Map One 

National Park Planner - Chesapeake and Ohio Canal National Historical Park, Lock 23  

National Park Service – Freshwater Sponges  

In Defense of Plants – Freshwater Sponges  

Maryland DNR – Islands of the Potomac Wildlife Management Area  

C&O Canal Trust – Riley’s Lock & Seneca – The Two-in-One Structure  

Wikipedia – Seneca Quarry  

Chesapeake & Ohio Canal National Historic Park

Chesapeake & Ohio Canal National Historical Park lets visitors explore history and the Potomac River along the 184 mile canal from Washington, DC to Cumberland, MD. There are a number of visitor centers and sites to visit all along the Potomac so take a look at them all.

Algonkian Regional Park

Algonkian Regional Park, located on the scenic Potomac River in Sterling, Virginia, is the perfect place for an afternoon of fun in the sun.

Seneca Creek State Park

The park, comprised of 6,300 acres, extends along 14 scenic miles of Seneca Creek. The Clopper Day-Use Area contains many scenic areas, including the 90-acre Clopper Lake, surrounded by forests and fields.

McKee-Beshers Wildlife Management Area

While much of the year McKee Beshers is popular with hunters, in early August several fields of sunflowers come into bloom drawing people from all around.


Saki has been exploring the Chesapeake Bay and its tributaries on kayak or stand up paddleboard (SUP) since 1999. He has competed in various races, organized and led numerous trips, and circumnavigated Kent Island both via kayak and SUP. Saki also enjoys nature photography, hiking, cross country skiing, raising chickens, beekeeping, and looking for new adventures. Saki's World is a great source of information about all these activities.

September 9, 2020

Main image: Rubble from Dam No. 2 forms Seneca Slackwater. All photos by Saki.
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