period of non-significant impact on the Earth system or on water resources (OA,
stage 1). The next stage is a period of accelerated degradation of the aquatic
environment and of water resources (AB, stage 2), often faster than population
growth in the river basin, first reaching the level of water quality (WQC 1 ) at which
water resources are impaired, often followed by a very poor level of water quality
(WQC 2 ). When the technical and regulatory measures taken by a society become
efficient, a proactive rehabilitation phase is observed after a stage of maximum
impact (BC, stage 3). When a satisfactory state is finally achieved, reaching the
desired level of quality WQC 1 , the regulation stage ensures a stable quality even
though the population and economy of the basin continue to grow (CD, stage 4).
If environmental management is insufficient, the impact can reach a permanent
degradation (BE, stage 5) stabilized at an altered level (>WQC 2 ), which can be
considered as irreversible.
The duration of the moderate environmental degradation (ED 1 ) from the societal
perspective is defined here as exceeding WQC 1 , and the duration of severe degradation (ED 2 ) as exceeding WQC 2 (Fig. 7). Water quality scales, WQC 1 and WQC 2 ,
defined for each of the issues recognized by the society may evolve over time,
thereby changing the environmental assessments made by societies. From an Earth
system perspective, the analysis may be quite different: Any significant deviation
from the pristine state, as defined by the background concentrations (C BGR ), is
expressing an alteration in the Earth system (ES A ) and may generate a change on
receiving waters – for instance, along the coastal zone.
4 Structuration of the Socioecological Research
in the Context of the PIREN-Seine
At the beginning of the programme in 1989, originally launched by hydrologists,
environmental chemists, biochemists, and engineers, only the natural processes, as
modified and sometimes regulated by present and past human activities, were
considered. After the seven stages of the programme, the interactions between the
society and its environment now account for a major aspect of our research. In some
projects we even aim to understand the generation and regulation of these activities,
a turning point that has been taken gradually in the second and third stages of the
programme. This comprehensive study of the Seine basin territory, a hydrological
and a social system, over a well-defined spatial entity, enables us to generate river
functioning models, which now implicitly include a number of socio-economic
variables (e.g. agricultural practices, consumers habits, and water use) and technical
changes or innovations (e.g. for wastewater treatment). Finally, in the last sixth and
seventh stages of the programme, the future state of the river has been explored on
the basis of narrative scenarios indicating the evolution of controlling factors,
sometimes coupled with the hydrological response to various climate change scenarios. These scenarios have been implemented in the modelling approaches.
Trajectories of the Seine River Basin
17
stage 1). The next stage is a period of accelerated degradation of the aquatic
environment and of water resources (AB, stage 2), often faster than population
growth in the river basin, first reaching the level of water quality (WQC 1 ) at which
water resources are impaired, often followed by a very poor level of water quality
(WQC 2 ). When the technical and regulatory measures taken by a society become
efficient, a proactive rehabilitation phase is observed after a stage of maximum
impact (BC, stage 3). When a satisfactory state is finally achieved, reaching the
desired level of quality WQC 1 , the regulation stage ensures a stable quality even
though the population and economy of the basin continue to grow (CD, stage 4).
If environmental management is insufficient, the impact can reach a permanent
degradation (BE, stage 5) stabilized at an altered level (>WQC 2 ), which can be
considered as irreversible.
The duration of the moderate environmental degradation (ED 1 ) from the societal
perspective is defined here as exceeding WQC 1 , and the duration of severe degradation (ED 2 ) as exceeding WQC 2 (Fig. 7). Water quality scales, WQC 1 and WQC 2 ,
defined for each of the issues recognized by the society may evolve over time,
thereby changing the environmental assessments made by societies. From an Earth
system perspective, the analysis may be quite different: Any significant deviation
from the pristine state, as defined by the background concentrations (C BGR ), is
expressing an alteration in the Earth system (ES A ) and may generate a change on
receiving waters – for instance, along the coastal zone.
4 Structuration of the Socioecological Research
in the Context of the PIREN-Seine
At the beginning of the programme in 1989, originally launched by hydrologists,
environmental chemists, biochemists, and engineers, only the natural processes, as
modified and sometimes regulated by present and past human activities, were
considered. After the seven stages of the programme, the interactions between the
society and its environment now account for a major aspect of our research. In some
projects we even aim to understand the generation and regulation of these activities,
a turning point that has been taken gradually in the second and third stages of the
programme. This comprehensive study of the Seine basin territory, a hydrological
and a social system, over a well-defined spatial entity, enables us to generate river
functioning models, which now implicitly include a number of socio-economic
variables (e.g. agricultural practices, consumers habits, and water use) and technical
changes or innovations (e.g. for wastewater treatment). Finally, in the last sixth and
seventh stages of the programme, the future state of the river has been explored on
the basis of narrative scenarios indicating the evolution of controlling factors,
sometimes coupled with the hydrological response to various climate change scenarios. These scenarios have been implemented in the modelling approaches.
Trajectories of the Seine River Basin
17