The Swiftwater (Limnen in Sindarin) arises in the White Mountains of Rohan and flows down into the Westfold, between Helm's Deep and Grimslade. It continues north, absorbing the Deeping-stream south of Marton, and then another river coming from Gapholt as well as the Grimbrook as it enters the Stonedeans. The river the flows northeast to west of Brockbridge, where it bends east. It flows into the Broadacres, continuing south of Stoke and on and to flow into the Entwash south of Eaworth.
The Swiftwater pours down from the White Mountains between Helm's Deep and Grimslade.
From there, the river flows along a ridge for a short stretch, then passes onto the plains of Rohan.
The Swiftwater is crossed by the road between Underharrow and Helm's Deep.
The first tributary of the Swiftwater is the Deeping-stream, flowing out from the Deeping-coomb.
Just to the north, another ford crosses the river. This is in fact the North-South Road between Fornost and Pelargir.
Another river flowing from Gapholt joins the Swiftwater's flow east of Marton.
As the Swiftwater passes into the Stonedeans, high cliffs rise on its western side.
The mill and bridge at Brockbridge are the next structures on the Swiftwater. The bridge is the only dry way to cross the river throughout the Stonedeans.
The Swiftwater next passes into the Broadacres, with the forest village of Direnfirel on its right bank.
The last bridge crossing the Swiftwater is the one between Stoke and Middlemead.
The last stretch of the river marks the border between the Broadacres and Kingstead.