Characterizing unsaturated flow from packed scoriated lapilli: Application to Strombolian cone hydrodynamic behavior

Abstract

Summary Over the past 30 years, numerous studies have been carried out into groundwater behavior in volcanic areas, with particular attention being paid to unsaturated volcanic tuffs. The volcanic formations of the Chaine des Puys (Massif Central, France) have long been regarded as valuable sources of fresh water and many aquifers associated with volcanic flows have been tapped for domestic water supply or as sources of bottled mineral water. It has often been postulated that these volcanic flows are recharged by groundwater from the volcanic cones located upstream, although no efforts have been made to validate this theory. We tested the physical basis of this hypothesis by characterizing the unsaturated hydrodynamic properties of the packed lapilli and scoria that form the most important constituents of the Strombolian cones in this area. The model derived from the results of the characterization experiments was compared with data obtained from a field site. The unsaturated properties of this site (Puy de Louchadiere Strombolian cone) are discussed qualitatively and in terms of “memory effect”. Further investigations are now needed to determine the exact behavior of the Strombolian cone and to produce complete models of the saturated and unsaturated zones of the aquifer system.