Evaluation of the socio-economical impacts of the Seine river low water periods

National audienceAn extensive study has been conducted in the recent years on the potential flood damage costs in the Parisian area [2]. We present here the first results of a further investigation focussed on the disturbances and the related costs for the river water users during low water periods. This study is mainly based on data given by the users themselves (drinking water and electricity producers, sewerage networks, shipping companies, fishers, administrations...). The analysis includes three steps (i) identification of the disrupting situations for each user, (ii) detailed description of the disturbances on the basis of realistic low water scenario, (iii) cost evaluation of these disturbances. The results obtained reveal no real stress on the use of water during low water periods despite the large amount of population and economical activities depending on the Seine river water : disrupting low water situations are rare and the induced costs are relatively modest. Besides, in many cases, the increase of the river discharge would not solve the problem encountered by the users and other more efficient technical solutions are available. These conclusions must nevertheless be taken with care : no severe low water period occurred during the last 3 or 4 decades. Such an event could not be studied since the users were not able to imagine it and extrapolate on its consequences