Flood and low-water management on the Orbe river

The Orbe is a river in the Jura, rising in the Rousses region of France and flowing through the canton of Vaud in Switzerland to Lake Neuchâtel. This karstic catchment area of around 475 km2 encompasses most of the issues associated with integrated water management: cross-border management, flood protection deficits, severe low-water problems, hydroelectric production, agricultural pumping for crop irrigation, fragile drinking water reserves in some places, recreational activities on and around bodies of water, navigation, a rich and protected natural environment, etc.

Gruner SA was commissioned to develop an overview of the hydraulic uses and weaknesses along the Orbe river. In coordination with the hydroelectric operators, the potential for using the lakes in the Vallée de Joux for flood control and as a reserve to support low-water levels during dry periods was also assessed. Apart from losses through infiltration into the karst, the level of the lakes is controlled solely by a water intake.

This study led to concrete proposals for managing the level of the lakes and the protective measures to be put in place to guarantee the safety of the population and the built environment downstream. An alarm plan is also being drawn up to ensure coordinated management of flood events by all the players involved (including the police, fire brigade, etc.).

During long periods without rain, drinking water supply problems are observed in the upper part of the catchment area (Vallée de Joux), while the lack of water in the tributaries prevents crop irrigation in the lower part (Orbe plain). Based on a statistical analysis of the flow data available for this watercourse and the volumes withdrawn, management proposals have been put forward for these periods of severe low water, so that all water uses are taken into account and can continue. The first constraint is to respect the residual flows and all the environmental objectives in the rivers.

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