The purpose of the study is to characterise the known severe lows in the upstream Seine watershed, to assess the impact of several lowland scenarios, including by taking into account likely developments related to global climate change, on the environments and socio-economic activities related to the basin’s water in order to assess the vulnerability of this territory to lowland situations, and to assess which pathways could be explored with a view to reducing this vulnerability, in particular through changes in the management of lakes and reservoirs upstream.