Great Lakes these waterways is heavy. Pleasure boats can also enter or exit the Great Lakes by way of the Erie Canal and Hudson River in New York. The Erie Canal connects to the Great Lakes at the east end of Lake Erie (at Buffalo, New York) and at the south side of Lake Ontario (at Oswego, New York). In 2009, the lakes contained 84% of the surface freshwater of North America; if the water were evenly distributed over the entire continent's land area, it would reach a depth of 1.5 meters (5 feet). The source of water levels in the lakes
Thames and Severn Canal and remains the fourth longest. There were always problems with water supply, as no reservoirs were built, while the summit section near the tunnel ran through porous limestone, and there were constant difficulties with leakage. Competition from the railways took much of the canal's traffic by the end of the 19th century, and most of the canal was abandoned in 1927, the remainder in 1941. Since 1972, the Cotswold Canals Trust has been working to restore both the canal and the Stroudwater Navigation, so that it can again provide a navigable link between the Thames and the Severn. A number