Volumes to be withdrawn from the Doux and Eyrieux basins

Similar project

Volumes to be withdrawn from the Doux and Eyrieux basins

Fulfill the requirements of the natural environment and its uses

Projet : 

The aim of the study is to define the volumes to be withdrawn from  the Doux and Eyrieux drainage basins in Ardèche, which allow for the requirements of the natural environment and its uses to be fulfilled on average of four years out of five. It is a matter of alligning requirements with resources by planning in order to avoid the reoccurence of crisis management (stoppage of withdrawal restrictions).


The monitoring of the study has been assured by a pilot committee comprised of State services, representatives from local authorities and users of the drainage basins.


The study was divided into  6 phases, a summary of which can be found below:


  • Phase 1: Caracterisaton of sub-basins and data collection
  • Phase 2: Summary of existing water withdrawals, analysis of their evolution. The available data about the withdrawals was analysed and completed in order to improve knowledge about them. The withdrawals could therefore be reconstituted for the period from 1997 – 2007 by distinguishing the resources used: direct withdrawal from the river by pumping, hillside storage or dams, ground water, deep water or non-basin resources.
  • Phase 3: Impact of the withdrawals and quantification of existing resources. The hydrological regime of the drainage basins is of the Mediterranean stormwater type,with a marked low water flow in July and August. Available natural resources and the impact of the withdrawals and discharges on these resources have been evaluated. The river flows downstream of the sub drainage basins were reconstituted thanks to the influence of the withdrawals (observable influenced flows) and in the hypothesis of the absence of withdrawal and discharge (natural flows).
  • Phase 4: Determination of minimum biological flows/aquatic environment requirements. Several species of local fish are present in the drainage basin including trout and souffia. A modelling of the evolution of the quality of the fishes’ habitat in relation to the flow at different representative points of the hydrographic network was undertaken. This analysis showed that low water hydrology is restrictive for the aquatic environment. The current situation must not be worsened by an increase in water withdrawals. In certain basins, water withdrawal must be reduced to increase the quality of the fishes’ habitat.
  • Phases 5 and 6: Determination of the volumes of withdrawable water and of the target low water flows; proposal for the breakdown of volumes by uses and a proposal for a single organism perimeter. Depending on the impact of the water withdrawals on the quality of the aquatic environment , two scenarios, subject to consultation, are proposed for the low water season (June – September) depending on the sub basins: the scenario of freezing the low water season withdrawals, which would mean maintaining the current level and the scenario of reducing the low water season withdrawals. Moreover, raising awareness of users to water savings must be carried out by stakeholders in the basins.
Mission : 
  • Steering committee, leading pilot and technical committees, leading of studies offices
  • Study and time-space reconstitution of agricultural collections
  • Hydrological study , influenced or not by withdrawals and discharges
  • Study of the scenarios of the reduction of withdrawals and their impact on hydrology
Le projet
Pays/région : 
Agence de l'Eau Rhône Méditerranée Corse
Période : 
Partenaires :