The lake is 15 km long and up to 4.1 km wide. Its surface area is
39.3 km2, the maximum depth 74 m. The lake is located at 429 metres above sea level. Lake Biel/Bienne has a catchment area of about
8,305 km2. Water remains in the lake for an average of 58 days. The rivers
Aare and
Zihl/
Thielle flowing from Lake Neuchâtel, the
Twannbach draining water down from the surplombing first Jura mountain range and the
Suze draining water down from the
Vallon de St. Imier, are the main tributaries. The
Aare was redirected into the lake in 1878, in order to prevent the flooding of the nearby area called "Seeland", and drains the water out of the lake down to
Büren through a simultaneously man-made channel. The level of all three lakes is being controlled by a dam built across the channel, in
Port. The lake contains the Île de St Pierre, where
Rousseau resided for a short time in 1765. Many traces of
lake-dwellings have been discovered on the shores of the lake. Today, the largest settlement along the shores of Lake Biel are the
bilingual city of
Biel/Bienne and its sister city
Nidau, both located on the northern end. The
St. Peter's Island attracts tourists. The island is located near
Erlach/Cerlier.
Jean-Jacques Rousseau once spent a few months on the island. One of the main business in the area is the watch and affiliated microtechnic industries. World famous watch brands have their sites and headquarters in the area, including the
Swatch Group and
Rolex movements manufacture. The lake's surface is the
lowest point of the canton of Neuchâtel. == Towns and villages by the lake ==