Geneva Lake
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GENEVA LAKE Ulrich Lemmin ENAC, Ecole Polytechnique Fédérale Lausanne (EPFL), Lausanne, Switzerland
Introduction Lake Geneva (local name: Lac Léman; Lacus Lemanus in Roman times) is a large, crescent shaped, deep lake of glacial origin, located between Switzerland and France (Figure 1). It is the largest lake in Western Europe, and it consists of a deep eastern main basin and a small, shallow, narrow western basin, locally called Grand Lac (Great Lake) and Petit Lac (Small Lake), respectively. Physical characteristics of the lake are summarized in Table 1. Lake Geneva is surrounded by the Jura Mountains to the northwest and by the Alps to the south. Most of the northern and western parts of the basin lie on a flat plateau. Steep alpine slopes, which rise to more than 1,000 m above the mean water level within 2 km of the shoreline, bound the lake basin to the east and southeast (Figure 1). The main basin is characterized by a large bottom plateau in the center, limited by the 300-m isobath (Figure 1). A N-S cross section of the lake basin changes gradually from a U shape with steeply sloping sides and a bed material mainly composed of large boulders in the east, to a V shape with gentle slopes, mainly composed of fine sands, in the west.
Most of the catchment area is located in the Alps to the east and south of the lake basin with elevations up to 4,000 m. The ratio of the catchment area to the lake surface is 12.7, and snowmelt in the spring is an important process of water renewal. The main inflow to the lake is the river Rhone, which enters the basin from the east. The rivers Aubonne and Venoge, flowing down from the Jura Mountains in the north, and the alpine river Dranse in the south are secondary contributors to the hydraulic load. The only outflow from the lake is the Rhone river in Geneva at the western end of the lake, where the water level of the lake is controlled by a weir. In the water mass balance, river inflow and outflow clearly dominate over precipitation and evaporation, making Lake Geneva a fluvial lake with a theoretical residence time of about 12 years.
Climate, windfield, and thermodynamic state Lake Geneva is situated in a temperate climate zone that is influenced by the Atlantic Ocean and the Mediterranean Sea. However, cold, dry air originating in the Siberian plains can make intrusions, mainly during the winter months. Monthly mean air temperature values range approximately from a minimum of 1 C in the winter to a maximum of 20 C in the summer. Annual mean air temperatures vary between 7 C and 12 C, with a longterm mean of 10.6 C. This has slightly increased over the past 30 years.
L. Bengtsson, R.W. Herschy, R.W. Fairbridge (eds.), Encyclopedia of Lakes and Reservoirs, DOI 10.1007/978-1-4020-4410-6, # Springer Science+Business Media B.V. 2012
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GENEVA LAKE
Geneva Lake, Figure 1 Satellite image showing Lake Geneva and the surrounding area. Main depth contours are shown. Arrows indicate mean wind directions.
Geneva Lake, Table 1 Physical characteristics of Lake Geneva Mean ge
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