Lake Biel or Lake Bienne (German: Bielersee, French: Lac de Bienne) is a lake in the west of Switzerland. Together with Lake Morat and Lake Neuchâtel, it is one of the three large lakes in the Jura region of Switzerland. It lies approximately at 47°5′N 7°10′E, at the language boundary between German & French speaking areas.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 has a catchment area of about 8,305 km². Water remains in the lake for an average of 58 days. The river Aare, the river Zihl/Thielle flowing from Lake Neuchâtel, the Twannbach draining water down from the surplombing first Jura mountain range and the river Suze draining water down from the Vallon de St. Imier, are the main tributaries. The river 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.