The Rhine's highest source, the Hinter Rhine, issues from the Rheinwaldhorn Glacier more than 11,000 ft (3,353 m) above sea level and joins the Vorder Rhine, flowing from Lake Tuma, to form the Rhine proper at Reichenau, S of Chur, Switzerland. From Chur the river flows N to Lake Constance and then W over the 65-ft (20-m) Rhine Falls at Schaffhausen (harnessed for hydroelectric power by the Swiss) to Basel, c.500 mi (800 km) from the North Sea.
At Basel the Rhine becomes the Upper Rhine of the Germans and turns sharply N to Mainz across the broad-floored Rhine rift valley, a large graben, or down-faulted block, between the Black Forest and the Vosges Mts. Navigation here is by way of a lateral canal through France as far as Strasbourg; below Strasbourg the riverbed has been improved for navigation. Below Mainz, at Bingen, Germany, the Rhine leaves the rift valley and flows for c.80 mi (130 km) across the Rhenish Slate Mts. in a steep gorge, famous for its scenery and wines, with castles surviving from times when tolls were levied on the river's traffic, and landmarks such as the Lorelei and the Drachenfels.
Beyond Bonn the river becomes the Lower Rhine of the Germans and emerges onto the North German Plain as a broad, sluggish, and increasingly polluted river flowing on a bed of deltaic deposits left by ancestors of the modern river. Efforts to solve the pollution problem began in the late 1970s and had achieved considerable, if not complete, success by the late 1990s.
Just below Emmerich, on the border with the Netherlands, the modern delta begins, and the Rhine breaks up into two major distributaries, the Lek and the Waal. The Lek, which becomes the Nieuwe Maas, continues W to Rotterdam and then by the canalized New Waterway enters the North Sea at Hoek van Holland (Hook of Holland). The Waal, which merges with the waters of the Maas to form the Merwede, also flows west; the Merwede and the Bergsche Maas join to form the Hollandschdiep, an arm of the North Sea, 6 mi (9.6 km) SE of Dordrecht. A third distributary, known as the Crooked Rhine, leads to Utrecht and continues west to the sea as the Old Rhine; it is linked with Amsterdam by the Amsterdam-Rhine Canal and thence by the North Sea Canal to the North Sea.