Dalecarlia Reservoir Auxiliary Pumping System

From Mike High's The C&O Canal Companion:

From the towpath follow the concrete-surfaced road down to the boulder-strewn floodplain. At the end of the path, a concrete platform offers a view of Little Falls—the rapids that likely ended John Smith's exploration up the Potomac in 1608. The army built the platform in the 1970s as part of an auxiliary system to fill the reservoir in the event of a drought.