The power of the Shannon, falling 100 feet in 15 miles from Killaloe to Limerick, is nowadays tapped by the hydroelectric power station at Ardnacrusha. But in earlier times it did not go entirely unused. I have already written about the bleach mill at Doonass; here is a page about the other bleach mill, at Clareville, and about the water works in the same area. These works are on a stretch of the Shannon navigable only by cots (then) and kayaks and canoes (now).
Irish waterways history 