@inproceedings{fdi:010091424,
  title = {{M}ultiple flow dynamics in karst aquifers following recharge events highlighted by dissolved gases - case of the {L}ez karstic system ({S}outh of {F}rance) [r{\'e}sum{\'e}]},
  author = {{P}erotin, {L}. and {D}e {M}ontety, {V}. and {L}adouche, {B}. and {B}ailly-{C}omte, {V}. and {L}abasque, {T}. and {C}hatton, {E}. and {B}ouchez, {C}. and {V}ergnaud, {V}. and {T}weed, {S}arah and {G}uilhe-{B}atiot, {C}. and {S}eidel, {J}.{L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{K}arstic aquifers are important reservoirs for water supply but their heterogeneous structure and very different flow velocities complicate their management. {G}eochemical tracers are various and give information of water origin and/or residence time. {A}mongst geochemical tracers, gas tracers are interesting since their solubility depends on physical conditions (temperature, pressure, salinity). {T}hey give information about recharge conditions ({R}echarge temperature and {E}xcess {A}ir) and physical processes as matrix/conduits flux exchanges. {T}he present work assesses the benefits of gaseous tracers to characterise the recharge dynamics in the {L}ez {K}arst aquifer, which is a complex system subjected to an active management




for the water supply and where multiple flow paths mix. {N}oble gases ({N}e, {A}r) and {N}2 were measured during autumnal recharge events of 4 hydrological cycles at a quasi-daily time-step from 2012 to 2016 at the spring outlet of the {L}ez system. {I}n addition, a high frequency (intra-day time step) monitoring by in-situ mass spectrometry was conducted at the {L}ez spring during the 2019 autumnal recharge event. {A}t the same time, {E}xcess {A}ir was measured in several boreholes representative of capacitive and transmissive karst compartments on the {T}errieu experimental site, located in the main aquifer feeding the spring. {A} peak of {H}e was observed at the spring one day after the autumnal recharge event, indicating a deep flow contribution by




piston effect. {B}etween three and five days after, the {N}oble {G}as {T}emperature increases of 5°{C}, associated with an increase of 222{R}n and of the natural organic matter fluorescence. {T}hese tracers indicate a contribution of fast infiltrated water from the surface under warmer recharge conditions compared to the water flowing at the spring during baseflow. {E}xcess air measured before and after the recharge show opposite trends between boreholes intersecting only matrix and those intersecting conduits, highlighting matrix/conduits flux exchanges. {T}hese results show the interest of gaseous tracers to discriminate flow origins and recharge dynamic during flood event in the karstic spring both at a local scale (matrix vs conduits) and at the catchment scale (deep flow, main aquifer and fast flow from surficial infiltration).},
  keywords = {{FRANCE}},
  numero = {},
  pages = {en ligne [1 ]},
  booktitle = {{G}oldschmidt 2021 conference report},
  year = {2021},
  DOI = {10.7185/gold2021.4840},
  URL = {https://www.documentation.ird.fr/hor/fdi:010091424},
}