Nant de Drance

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Nant de Drance
Nant de Dranse, Drance brook
The Nant de Drance flows into the Emosson reservoir, in the picture on the left (southern) edge in the bay behind the headland

The Nant de Drance flows into the Emosson reservoir, in the picture on the left (southern) edge in the bay behind the headland

Data
Water code CH : 3965
location Switzerland
River system Rhone
Drain over Barberine  → Eau Noire  → Trento  → Rhone  → Mediterranean
source Outflow of Lac du Vieux Emosson
46 ° 3 ′ 45 ″  N , 6 ° 53 ′ 54 ″  E
Source height 2205  m above sea level M.
muzzle in the Lac d'Emosson coordinates: 46 ° 3 ′ 53 "  N , 6 ° 54 ′ 42"  E ; CH1903:  559 218  /  101606 46 ° 3 '53 "  N , 6 ° 54' 42"  O
Mouth height 1930  m above sea level M.
Height difference 275 m
Bottom slope 21%
length 1.3 km
Catchment area 5.47 km²
Discharge at the estuary
A Eo gauge : 5.47 km² 		MQ
Mq
 		160 l / s
29.3 l / (s km²)

The Nant de Drance is a torrent in the Valais Alps , which runs in the border area between Switzerland and France . It rises on the slopes of Alp Vieux Emosson and flows into the Barberine at Emosson as a right tributary . Since 1955 it has been the drain of the Vieux Emosson reservoir and since 1974 it flows into Lac d'Emosson . This has halved the length of the Nant de Drance. Today the brook is part of the extensive power plant system of Electricité d'Emosson in Haute-Savoie and Lower Valais .

power plant

Since September 2008, Nant de Drance SA has been building a pumped storage power plant between the two lakes . The power plant is to be commissioned in stages from 2021. The water that is already routed down into the valley in a tunnel is used, or water is pumped from Lake Emosson to Lake Vieux-Emosson. According to the power plant company , "natural waters [...] are not affected by water use in the closed circuit between the two reservoirs."

The dam wall of the Vieux-Emosson reservoir was increased by 20 m from 45 m, whereby the capacity could be doubled to 25 million m³. This amount of water is sufficient to operate the pumped storage power plant with 900 MW for about 20 hours without interruption. The lower reservoir is the Lac d'Emosson , which at 227 million m³ is around nine times as large as the upper basin.

The pumped storage plant consists of 6 Francis pump turbines of 150 MW each (in combination with double-fed asynchronous machines with adjustable speed of 175 MVA), which can switch from full-load turbine operation to full-load pump operation in less than 10 minutes. It has an efficiency of over 80% and is expected to generate around 2.5 TWh of annual work. The planned investment volume is CHF 1.9 billion.

Situation map

Map of the power plant systems at Lac d'Emosson . The Nant de Drance power plant is shown in green , the Electricité d'Emosson SA systems in blue , and the Barberine-Vernayaz power plant owned by SBB in red .

Web links

Individual evidence

  1. ↑ a b Geoserver of the Swiss Federal Administration ( information )
  2. ↑ Hydrological Atlas of Switzerland of the Federal Office for the Environment FOEN, Table_13
  3. ↑ a b Modeled mean annual discharge. In: Topographical catchment areas of Swiss waters: sub-catchment areas 2 km². Retrieved August 25, 2017 .
  4. ↑ http://www.nant-de-drance.ch/de/projekt/umwelt/ (November 15, 2017).
  5. ↑ Vieux-Emosson dam increased by 20 meters, press release from 2014-09-25