Karst flow processes explored through analysis of long-term unsaturated-zone discharge hydrochemistry: a 10-year study in Rustrel, France

Exploración de los procesos de flujo kárstico en la zona no saturada mediante el análisis de la hidroquímica de la descarga a largo plazo: un estudio de 10 años en Rustrel, Francia

Etude des processus d’écoulement karstique à l’aide de l’analyse de l’hydrochimie à long terme à la base de la zone non saturée: une étude de 10 ans à Rustrel, France

Processos de fluxo carstico explorados por meio de análise hidroquímica de longo prazo de zona de descarga não saturada: um estudo de 10 anos em Rustrel, França

Aurore Perineau Barbel-Périneau (1, 2, 3) , Laurent Barbiero (4, 5) , Charles Danquigny (1, 2, 3) , Christophe Emblanch (1, 2, 3) , Naomi Mazzilli (1, 2) , Milanka Babic (1, 2, 3) , Roland Simler (1, 2, 3) , Vincent Vallès (1, 2)

1 EMMAH - Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes
2 AU - Avignon Université
3 SNO Karst - Service National d'Observation sur le KARST
4 GET - Géosciences Environnement Toulouse
5 IRD - Institut de Recherche pour le Développement

The unsaturated zone of karst aquifers influences the dynamics and the chemistry of water. Because of a lack of direct access, other than via caves, flows in the aquifer matrix and the smallest conduits remain poorly characterized. The few artificial underground structures in the unsaturated karst provide a rare opportunity to study the variety of flow processes. At the low noise underground research laboratory (Laboratoire Souterrain à Bas Bruit, LSBB) in Rustrel (France), 12 variables (temperature, pH, electrical conductivity, alkalinity, major anions and cations, total organic carbon) have been monitored on 12 perennial or temporary flows and leakages over a 10-year period covering contrasting climatic periods. This unique dataset of 1,135 samples has been used to discriminate, identify, and rank the processes associated with the hydrochemical variability of these different types of flows. A principal component analysis and a hierarchical cluster analysis, using mean values and standard deviation of the flow along the principal components, were performed. The results indicate that seasonal variability, mean water residence time, and the depth of acquisition of the chemical characteristics are the main factors of the variability of chemistry at the monitored flow points. Distinguished clusters highlight the great diversity of flows and processes occurring in the fine pathways that may be neighboring the large and structured fractures and conduits. Long-term monitoring with various climatic conditions appears to be a useful tool for assessing this diversity.

Mots clés: Karst; Groundwater statistics; Unsaturated zone; Hydrochemistry; Groundwater monitoring; forkarst

Domaines: Environnement et Société; Milieux et Changements globaux; Interfaces continentales, environnement

Aurore Perineau Barbel-Périneau, Laurent Barbiero, Charles Danquigny, Christophe Emblanch, Naomi Mazzilli, et al.. Karst flow processes explored through analysis of long-term unsaturated-zone discharge hydrochemistry: a 10-year study in Rustrel, France. Hydrogeology Journal, 2019, 27 (5), pp.1711 - 1723. ⟨10.1007/s10040-019-01965-6⟩. ⟨hal-02082742⟩