Towards operational hydrology for a thorough spatio-temporalexploration of the Critical Zone

International audienceOver the last century, the Critical Zone faced remarkable climate and land use changes increasing the pressures onthe Hydrosphere and giving rise to numerous environmental consequences in terms of water quantity and quality.From now on, the Critical Zone must face the challenge to supply 9 billion people with quality food and safedrinking water in a context of global warming. For the Hydrosphere, this challenge could be addressed with abetter understanding of the dynamics and resilience of aquatic environments (rivers, lakes, groundwaters, oceans).In view of the spatial and temporal variety and variability of flow dynamics and biogeochemical reactions occur-ring in the Hydrosphere a new investigation method is needed. This study approaches the concept of “operationalhydrology” aiming to enhance either the spatio-temporal distribution and the quality of environmental data for athorough exploration of the Hydrosphere.To illustrate our approach, we present natural and anthropogenic dissolved gas data (He, Ne, Ar, Kr, Xe, N2, O2,CO2, CH4, N2O, H2, BTEX, and some VOCs) measured in situ with a CF-MIMS (Chatton et al, 2016) installedin a mobile laboratory arranged in an all-terrain truck (CRITEX-Lab). This ongoing work focuses on groundwaterand the field investigation of residence time distributions, recharge processes (origins), water flow paths andmixing, biogeochemical reactivity and contamination (sources).The rationale behind “operational hydrology” could be applied to the field measurement at high-frequency ofmany other environmental parameters (temperature, cations, anions, isotopes, micro-organisms) not only for theinvestigation of groundwaters but also rivers, lakes and oceans.Eliot Chatton, Thierry Labasque, Jerome de La Bernardie, Nicolas Guihe neuf, Olivier Bour and LucAquilina; Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics andBiogeochemistry of Groundwater Flow; Environmental Science & Technology, in press, 2016