 Between these two northern ridges is Blea Tarn.A large pool of about depth, Blea Tarn provides the main feed for the more famous beauty spot of Watendlath Tarn.Drainage to the east (and Thirlmere) is provided by Ullscarf and Launchy Gills, the former flowing via the secluded Harrop Tarn within the Thirlmere Forest.