All activities on the river are forbidden during the lowering of the reservoirs.
The river changes colour when the reservoirs are being lowered and the submerged parts become visible. Care remains the byword: it is forbidden to practice any nautical activity and it is dangerous to approach the river.
During these operations, navigation, bathing and angling on the bypassed sections of the Rhone at Chautagne, Belley and Brégnier-Cordon and all other nautical activities on the Rhone are forbidden by Prefectural ruling.
Access to the emerged parts of the reservoirs is forbidden. Access to certain banks and quays can also be restricted by municipal decision to ensure the safety of all.
Although usually hidden areas can be discovered, it is dangerous to venture onto the bed of the Rhone, and on the islets and gravel banks. The assistance operations can be interrupted at any time in the case of floods, overshooting of the threshold for suspended matter in the water or an incident in a hydropower plant. The water can rise very quickly in these cases.
CNR has installed panels at different points of the river to remind the public of these vital rules.
The presence of suspended matter causes the colour and appearance of the water to change: it is darker, between brown and grey. An unusual smell may emanate from the river at certain points.
The river returns to its usual appearance a short time after the operations have ended.