higher up the mountains. It is expected that the continuous input of sediment into the lake will silt up the lake. This has already happened to the former Lake Tuggenersee. The cut-off Old Rhine at first formed a swamp landscape. Later an artificial ditch of about two km was dug. It was made navigable to the Swiss town of Rheineck. Lake Constance Lake Constance consists of three bodies of water: the Obersee ("upper lake"), the Untersee ("lower lake"), and a connecting stretch of the Rhine, called the Seerhein ("Lake Rhine"). The lake is situated in Germany, Switzerland and Austria near the Alps. Specifically, its shorelines lie in the German states of Bavaria and Baden-Württemberg, the Austrian state of Vorarlberg, and the Swiss cantons of Thurgau and St. Gallen. The Rhine flows into it from the south following the Swiss-Austrian border. It is located at approximately . Obersee The flow of cold, grey mountain water continues for some distance into the lake. The cold water flows near the surface and at first doesn't mix with the warmer, green waters of Upper Lake. But then, at the so-called Rheinbrech, the Rhine water abruptly falls into the depths because of the greater density of cold water. The flow reappears on the surface at the northern (German) shore of the lake, off the island of Lindau. The water then follows the northern shore until Hagnau am Bodensee. A small fraction of the flow is diverted off the island of Mainau into Lake Überlingen. Most of the water flows via the Constance hopper into the Rheinrinne ("Rhine Gutter") and Seerhein. Depending on the water level, this flow of the Rhine water is clearly visible along the entire length of the lake. The Rhine carries very large amounts of debris into the lake. In the mouth region, it is therefore necessary to permanently remove gravel by dredging. The large sediment loads are partly due to the extensive land improvements upstream. Three countries border the Obersee, namely Switzerland in the south, Austria in the southeast and the German states of Bavaria in the northeast and Baden-Württemberg in the north and northwest. Seerhein The Seerhein is only long. It connects the Obersee with the 30 cm lower Untersee. Distance markers along the Rhine measure the distance from the bridge in the old city center of Constance. For most of its length, the Seerhein forms the border between Germany