EGU2020-5986
https://doi.org/10.5194/egusphere-egu2020-5986
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Evolution of river pollutions under the influence of local hydro-climatic changes - the example of the Bienne River (Jura Mountain, France)

Elie Dhivert1, François Gibon1, Karine Hochart1, and Bertrand Devillers2
Elie Dhivert et al.
  • 1Anthropo-Crisis Institute, 235 route de St Claude 39130 ETIVAL, France
  • 2Haut-Jura Natural Regional Park, 29 le Village 39310 LAJOUX, France

In application of the EU Water Framework Directive, many actions have been undertaken in order to reduce pollution levels in river systems. However, for certain catchments, the resilience process is not occurring as expected. In the Bienne River basin, metals discharge has plummeted since the 1990s, following the implementation of a better industrial waste management, as well as an important industrial restructuring. Nevertheless, this river has been regularly affected by massive fish mortality over the 2012-2019 period. This phenomenon, never identified before, is becoming recurrent. Organic tissues sampled in dead fish contained high concentrations of metals in association with other toxics. In this context, this study introduces a transdisciplinary approach in order to: (i) analyse spatial and temporal evolutions of pollutions in the Bienne River, (ii) evaluate potential ecotoxicological impacts associated, (iii) identify interactions with local hydro-climatic changes. Metallic and organic pollutants were analysed over different stations and at multi-temporal scales, associating sedimentary archives, suspended matters and passive water samplers. These analyses highlight the impact on the river quality of both current and legacy pollutions, particularly during prolonged low-water periods and high discharge events. Ecotoxicological analyses emphasize a severe risk level in the case of polluted sediments remobilization, especially because of heavy metals and PAH contamination. Geochemical evidence of such remobilization events has been recorded over the last decade in a sedimentary core sampled in the downstream part of the Bienne River. Hydrological data recorded in the Bienne River gauging stations since 1971 attests of an important year-to-year variability, although changes in the river discharge distribution are ongoing. Data has shown a higher frequency of both the lowest and the highest outflows over the 2012-2019 period compared to the rest of the hydrological recording. Hydro-climatic variables coming from in-situ measurements and satellite data (GPM-IMERG6) has also shown significant modifications in the rainfall regime over this period, especially in the augmentation of dry spells and heavy rainfall episodes. Those modifications agree well with the discharge change observations. This study brings out knock-on impacts of combined geochemical, ecotoxicological and hydro-sedimentary issues on the fate of aquatic ecosystems, especially under the influence of local hydro-climatic changes and their implications on hydrological regimes. Those results aim at reducing uncertainties concerning the evolution of the river quality by highlighting such a tipping point for environmental conditions. In addition, such a study helps us to grasp the complexity of local stakes regarding the multiple interests of a wide range of stakeholders and policy makers involved on the field.

How to cite: Dhivert, E., Gibon, F., Hochart, K., and Devillers, B.: Evolution of river pollutions under the influence of local hydro-climatic changes - the example of the Bienne River (Jura Mountain, France), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5986, https://doi.org/10.5194/egusphere-egu2020-5986, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 15 Apr 2020
  • CC1: Comment on EGU2020-5986, Coline Poppeschi, 04 May 2020

    Thanks for your presentation. During the chat time of this session, you mention that in the future you expect an increase of the frequencies and duration of low water and also stronger rainfall episodes. Please, can you tell me what bibliographic resources/observations you rely on? 

    • AC1: Reply to CC1, Elie Dhivert, 04 May 2020

      Thank for your interest. Currently we are working on a better evaluation of hydro-climatic changes affecting the Jura Mountains. We use datasets comming from gauging stations and satellites (IMERG and ERA5). The study is on progress, we observe an increase of dry spells in link with longer and more frequent low water episods since 1970s, and also changes in the rainfall distribution. Theses changes are not linear but show differents incressing steps over the recording period.