Pluri-annual Water Budget on the Seine Basin: Past, Current and Future Trends

Abstract

The trajectory of the Seine basin water resources is rebuilt from the early 1900s to the 2000s before being projected to the end of the twenty-first century. In the first part, the long-term hydrological data of the Paris gauging stations are analysed beginning in 1885, highlighting the effect of anthropogenic water management on the Seine River discharge. Then a detailed water budget of the Seine basin is proposed. It quantifies for the first time the water exchanges between aquifer units and the effect of water withdrawals on river–aquifer exchanges. Using this model, the trajectory of the system is evaluated based on a downscaled climate reanalysis of the twentieth century and a reconstruction of the land use in the early 1900s, as well as the choice of a climate projection which favours the model that best reproduces the low frequency of precipitation. The trajectory is synthesised as average regimes, revealing a relative stability of the hydrosystem up to the present, and drastic changes in the discharge regime in the future, especially concerning the decreased amount of low flow and its increased duration. These expected changes will require the definition of an adaptation strategy even though they are rather limited in the Seine basin when compared to other French regions.

Trajectories of the Seine River Basin

“…This information supported the reconstruction of nutrient circulations (nitrogen and phosphorus) in the basin at a fine spatio-temporal resolution [46]. Changes in land cover since the beginning of the twentieth century were also used to reconstruct the evolution of the Seine basin water budget [32].…”

“…The hydrological regime of the Seine River basin is pluvial/oceanic. The mean rainfall over the basin is 800 mm year À1 and exhibits some spatial variability, with a maximum of around 1,200 mm year À1 along the coastal shoreline and in the Morvan mountainous range and only 650 mm year À1 in its central part [30][31][32]. For the past 50 years, the Seine discharge at the last gauging station before the estuary at Poses has had an average value of 485 m 3 s À1 but reached 2,280 m 3 s À1 in winter, with summer minimums at 80 m 3 s À1 (low flows sustained by reservoirs).…”

“…25 m 3 s À1 discharge downstream of Paris). Water management is therefore a key factor of the current Seine River discharge profile [32]. It should be noted that the relative natural dilution power of the Seine River in relation to Parisian wastewaters is very limited, making the Seine River sensitive to point source pollution compared with most large European rivers.…”

“…Widely developed within the PIREN-Seine, e.g. for water budget [32], oxygen budgets [41], or nitrogen circulation at the watershed level [46], this approach remains original within the scientific community.…”

Ecological Functioning of the Seine River: From Long-Term Modelling Approaches to High-Frequency Data Analysis

“…Whereas [14][15][16][17] investigated the vertical dimension, i.e. water and nutrient exchanges between aquifers and surface water [18,19] in the context of a multi-scale view of stream-aquifer interfaces [20], the fourth dimension, which provides the time scale, has long been a major concern of the PIREN-Seine program, both in terms of past and future scenario analysis [21,22]. The Seine River system is a textbook example illustrating this overall vision.…”