2.1 Strategies Devised by PIREN-Seine Scientists
for the Spatiotemporal Observation of the River Basin
2.1.1 Multiple and Nested Spatial Scales to Address River Basin
Functioning
The first rationale of data acquisition is spatial and complements data from the Seine
Water Agency, which is based on major rivers and urban areas in the 1980s.
Scientists have combined a wide range of spatial scales from plots or specific
point sources to the whole Seine basin up to the basin outlet (see Fig. 10 in [5]).
The upstream–downstream Paris river profile, a stretch under maximum pressure, is
still a permanent feature of the programme.
2.1.2 Multiple and Complementary Temporal Scales to Address River
Basin Functioning, Regulatory Surveying and Reporting
This second approach overlaps with the previous one. Scientists addressing the
functioning of the system select the most appropriate temporal scales to cover the
dominant control factors and/or river processes (Fig. 1). The hydrological phenomena are reported on the daily scale, thanks to the regulatory hydrometeorological
networks. Sub-daily observation is needed in headwater streams and for storm
events in urbanized areas. At the beginning of the project, intensive fieldwork was
carried out over short periods, as impact studies, quarterly longitudinal profiles and
bimonthly samplings performed at key stations (e.g. near the laboratory).
Hydrologically driven variability also depends on the size of the river basin
intercepted at the station: flood duration ranges from a few hours for headwater
streams to a few weeks for large basins (100,000 km
2 ). Internal processes within the
river, such as phytoplankton blooms and autochthonous formation of organic and/or
inorganic particulates, last between a few days and weeks or more. Scientists are also
interested in interannual variability (dry compared to wet years).
This temporal approach is largely finer than that of the regulatory chemical water
quality surveys performed by river basin authorities, centralized on the monthly
scale, whatever the size of the basin at the control station. Therefore, these surveys
rarely capture sub-seasonal variability, and some of the river controlling factors are
only taken into account statistically. Daily and sub-daily records are made by the
water industries at the river intakes, on treated sewage and downstream of their
outflows. These records, which are compiled for industrial monitoring or accident
detection, are generally not included in river survey processing and annual or
interannual state-of-the-environment reports (SOE; Fig. 1).
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C. Carré et al.
for the Spatiotemporal Observation of the River Basin
2.1.1 Multiple and Nested Spatial Scales to Address River Basin
Functioning
The first rationale of data acquisition is spatial and complements data from the Seine
Water Agency, which is based on major rivers and urban areas in the 1980s.
Scientists have combined a wide range of spatial scales from plots or specific
point sources to the whole Seine basin up to the basin outlet (see Fig. 10 in [5]).
The upstream–downstream Paris river profile, a stretch under maximum pressure, is
still a permanent feature of the programme.
2.1.2 Multiple and Complementary Temporal Scales to Address River
Basin Functioning, Regulatory Surveying and Reporting
This second approach overlaps with the previous one. Scientists addressing the
functioning of the system select the most appropriate temporal scales to cover the
dominant control factors and/or river processes (Fig. 1). The hydrological phenomena are reported on the daily scale, thanks to the regulatory hydrometeorological
networks. Sub-daily observation is needed in headwater streams and for storm
events in urbanized areas. At the beginning of the project, intensive fieldwork was
carried out over short periods, as impact studies, quarterly longitudinal profiles and
bimonthly samplings performed at key stations (e.g. near the laboratory).
Hydrologically driven variability also depends on the size of the river basin
intercepted at the station: flood duration ranges from a few hours for headwater
streams to a few weeks for large basins (100,000 km
2 ). Internal processes within the
river, such as phytoplankton blooms and autochthonous formation of organic and/or
inorganic particulates, last between a few days and weeks or more. Scientists are also
interested in interannual variability (dry compared to wet years).
This temporal approach is largely finer than that of the regulatory chemical water
quality surveys performed by river basin authorities, centralized on the monthly
scale, whatever the size of the basin at the control station. Therefore, these surveys
rarely capture sub-seasonal variability, and some of the river controlling factors are
only taken into account statistically. Daily and sub-daily records are made by the
water industries at the river intakes, on treated sewage and downstream of their
outflows. These records, which are compiled for industrial monitoring or accident
detection, are generally not included in river survey processing and annual or
interannual state-of-the-environment reports (SOE; Fig. 1).
384
C. Carré et al.