management and planning decisions. Two main tools, Seneque–Riverstrahler and
ProSe, have been developed with the PIREN-Seine partners in explicit consultation.
The first use of a PIREN-Seine model as a decision-making tool was that of
Seneque–Riverstrahler, at the beginning of the programme, to reflect on the different
wastewater treatment options with the AESN and the SIAAP, the latter institution
being in charge of the Parisian WWTPs. The model represents the major biogeochemical mechanisms of large watersheds involved in basic water quality (nutrient
status, organic pollution and oxygen deficit, eutrophication). Calculations of the
ecological processes are performed at a time scale of a few minutes, but results at the
ecosystem scale are provided at a resolution of 10-day time stages.
Seneque–Riverstrahler (S–RS) was used to support water managers by simulating specific planning scenarios aimed at optimizing wastewater treatment in order to
fulfil the implementation of the Urban Waste Water Treatment Directive in 1991 and
the Water Framework Directive (WFD) in 2000. Eutrophication and oxygen depletion in the river were significantly improved, facilitating the production of drinking
water and allowing for an increase in the number of fish species in the most humanimpacted area of Paris and its outskirts.
To allow its use by technicians, the Riverstrahler calculation model is embedded
in a GIS environment (Seneque; [23]), a software tool that has been transferred to the
Seine Water Agency (AESN) and used at the basin scale for their needs. S–RS has
also been used as part of the AESN reporting requirements for good-water-status
data to the European Union. It made it possible to simulate physicochemical data for
river waterbodies not monitored by measuring stations.
ProSe: The fine-scale impact of Paris wastewaters on the Seine River. The ProSe
model was developed from the first stage of the programme, at the request of the
SIAAP, on strongly human-impacted sections of the watercourse in order to be able
to deal with transitional situations, such as rainstorms and the discharges from the
Parisian combined sewers and the bypasses of WWTP in the Seine. It differs from
the Riverstrahler model in many ways: (1) It is a two-dimensional (2D) model based
on a specific, detailed morphological description at a resolution of 100 m; (2) it
simulates highly transient events with time steps of a few minutes, averaged at the
hourly scale. Dozens of combined sewage overflows, which are active during
rainstorms, are localized in this model. The hydraulic behaviour of each stretch is
dynamically calculated by Saint–Venant equations, and its upstream limit conditions
are derived either from direct observations or from Riverstrahler simulations
[17]. The biogeochemical processes (e.g. bacterial degradation of organic matter)
are modelled through the RIVE model in the same way as in Riverstrahler. Today, it
simulates basic water quality through more than a dozen physical chemical, biogeochemical and microbial indicators. It now covers a major section of the Seine and its
tributaries within and downstream of Paris to the basin outlet.
ProSe is currently used to optimize the interannual development and sub-daily
management of the sewage treatment works for the whole Paris region and its impact
on water quality over several hundreds of kilometres of river length (Seine, Marne,
Oise). The SIAAP operates the model to test the aquatic environment of new
phosphorus and nitrogen treatments required by EU Directives for their WWTP
394
C. Carré et al.
ProSe, have been developed with the PIREN-Seine partners in explicit consultation.
The first use of a PIREN-Seine model as a decision-making tool was that of
Seneque–Riverstrahler, at the beginning of the programme, to reflect on the different
wastewater treatment options with the AESN and the SIAAP, the latter institution
being in charge of the Parisian WWTPs. The model represents the major biogeochemical mechanisms of large watersheds involved in basic water quality (nutrient
status, organic pollution and oxygen deficit, eutrophication). Calculations of the
ecological processes are performed at a time scale of a few minutes, but results at the
ecosystem scale are provided at a resolution of 10-day time stages.
Seneque–Riverstrahler (S–RS) was used to support water managers by simulating specific planning scenarios aimed at optimizing wastewater treatment in order to
fulfil the implementation of the Urban Waste Water Treatment Directive in 1991 and
the Water Framework Directive (WFD) in 2000. Eutrophication and oxygen depletion in the river were significantly improved, facilitating the production of drinking
water and allowing for an increase in the number of fish species in the most humanimpacted area of Paris and its outskirts.
To allow its use by technicians, the Riverstrahler calculation model is embedded
in a GIS environment (Seneque; [23]), a software tool that has been transferred to the
Seine Water Agency (AESN) and used at the basin scale for their needs. S–RS has
also been used as part of the AESN reporting requirements for good-water-status
data to the European Union. It made it possible to simulate physicochemical data for
river waterbodies not monitored by measuring stations.
ProSe: The fine-scale impact of Paris wastewaters on the Seine River. The ProSe
model was developed from the first stage of the programme, at the request of the
SIAAP, on strongly human-impacted sections of the watercourse in order to be able
to deal with transitional situations, such as rainstorms and the discharges from the
Parisian combined sewers and the bypasses of WWTP in the Seine. It differs from
the Riverstrahler model in many ways: (1) It is a two-dimensional (2D) model based
on a specific, detailed morphological description at a resolution of 100 m; (2) it
simulates highly transient events with time steps of a few minutes, averaged at the
hourly scale. Dozens of combined sewage overflows, which are active during
rainstorms, are localized in this model. The hydraulic behaviour of each stretch is
dynamically calculated by Saint–Venant equations, and its upstream limit conditions
are derived either from direct observations or from Riverstrahler simulations
[17]. The biogeochemical processes (e.g. bacterial degradation of organic matter)
are modelled through the RIVE model in the same way as in Riverstrahler. Today, it
simulates basic water quality through more than a dozen physical chemical, biogeochemical and microbial indicators. It now covers a major section of the Seine and its
tributaries within and downstream of Paris to the basin outlet.
ProSe is currently used to optimize the interannual development and sub-daily
management of the sewage treatment works for the whole Paris region and its impact
on water quality over several hundreds of kilometres of river length (Seine, Marne,
Oise). The SIAAP operates the model to test the aquatic environment of new
phosphorus and nitrogen treatments required by EU Directives for their WWTP
394
C. Carré et al.