* Climate change brings drought and floods on Rhone
* French CNR to boost renewables capacity five-fold
* Wind and solar to compensate fall in hydropower
By Geert De Clercq
PARIS, March 6 (Reuters) - French hydropower firm CNR, anticipating the impact of climate change and the possible disappearance of glaciers in the Swiss Alps, plans to sharply increase its solar and wind capacity to compensate for lower water levels on the Rhone river.
The Rhone, running from Lake Geneva to the French Mediterranean, is one of Europe's biggest rivers but also one of the most exposed to climate change as it is fed mainly by Alpine glaciers, which are shrinking due to global warming.
An exceptional drought last year reduced water flow by 27 percent and reduced electricity production at the Compagnie Nationale du Rhone (CNR) hydropower group by the same percentage to 10.7 terawatthours, compared to 17.4 TWh in record year 2013.
Some scientists forecast the Rhone's flow to fall by 10 to 40 percent in coming decades and also see more violent swings in flow rates as droughts alternate with floods.
"Scientists say the Alps' glaciers could disappear by the end of the century. That does not mean they will, but we must act responsibly," CNR CEO Elisabeth Ayrault told Reuters on the sidelines of a briefing for energy reporters.
To make up for this, CNR plans to boost its renewables capacity five-fold.
"Our plan is to have as much capacity away from the river as on the river, probably by 2035," she said.
CNR has 3,035 megawatt (MW) of hydropower capacity - making it France's second-biggest hydropower producer after EDF - and has already built some 600 MW of mainly wind and some solar power since 2015.
By 2020, it wants to boost that to 1,000 MW and then accelerate renewables investment with a further 1,500 MW in 2020-25 to eventually reach 3,000 MW of renewables capacity.
Ayrault said the problem was not just slower flow rates but also increasing volatility. Last year's drought was followed by three major floods in December-January. Floods also weigh on output, as CNR is forced to open dams to evacuate excess water.
"What is worrying is the huge swings in river flow. We no longer have the regularity we had before," she said.
Ayrault said the irregular flow also affects other industries, such as nuclear energy, agriculture and shipping.
In the past 18 months, France twice had to ask Switzerland to increase the outflow of Lake Geneva to ensure sufficient cooling water for the Bugey nuclear plant, she said.
Owned 49.97 percent by gas utility Engie, 33.2 percent by state financial group Caisse des Depots and 16.83 percent by local authorities, CNR accounts for 25 percent of French hydropower output and has a monopoly on Rhone river hydropower under a concession that runs till 2023. (Reporting by Geert De Clercq; Editing by Adrian Croft)