Emissions de gaz à effet de serre (GES) dans les réservoirs et conséquences sur la qualité de l’eau des rivières à l’aval : bilan et modélisation

Title: Greenhouse gas (GHG) emissions from reservoirs and implications on the downstream river water quality: budget and modelling

Keywords: reservoirs ecological functioning, emissions of CO2, CH4, N2O, modelling water quality, integrating reservoirs and river models.

Main description: The second half of the twentieth century saw the emergence of numerous large dams designed to retain water in hydrosystems for a variety of uses: irrigation, hydroelectricity, support for low flows or flood protection, all of which justify human (as opposed to natural) management of flows in river basins. By altering the geomorphology of the landscape, reservoirs have a significant impact on the hydrological regime of downstream rivers, as well as on the overall biogeochemical functioning of hydrosystems.
A first step of the Ph-D aims at (i) quantifying greenhouse gas emissions from global reservoirs according to a typology based on latitude, age, etc., and at (ii) analysing the uncertainties of these estimates. The study will then focus on the implementation of GHG in an existing reservoir model (BARMAN). Integrating this reservoir model in the riverine RIVERSTRAHLER model will allow to calculate (i) nutrients retention in the reservoirs, (ii) the effects of reservoir water release on the downstream river water. GHG data will be newly collected from the reservoirs in the Seine basin and will be used for validation.
A prospective aspect will then allow us to examine the strategies to be adopted in terms of water regulation (small vs. large reservoirs) in relation to the adaptation of uses and management objectives of these reservoirs under e.g. climate change.