Author(s)

M Hochart, C Bertrand, M Dubar, Y Guglielmi & V Merrien-Soukatchoff

Abstract

Nice airport was fitted out on the holocene Var delta, upright a coastal alluvial sheet which feeds the low Var valley and Nice city. The geometrical limits and deltaic deposits of the reservoir were determined from geologic bore holes. Intercommunications between levels allow exchanges from superficial to intermediate parts of the reservoir which is surmounted by a human developed reservoir allowing a contact between the alluvial sheet and the sea. The natural south and east-west drainage of the water table is modified by embankments and pumpings. The alluvial sheet waters chemistry allows for the distinguishing of the zones influenced by a mixture of chlorinated sodic sea waters, bicarbonate calcic alluvial waters and sulphate calcic surface waters. The influence of pumpings is translated by high contents in chlorides (113 to 304 mg/L). The isotopic study allowed to redraw the waters origin (O18) and to date them (T). Former waters (7,46%0<[O18]<7,25%0) issued of fast mixtures of the water table with surface waters (10,01%0~[O18]<9,50%0) divide up according to an east- west central axis and are surrounded with younger waters (6<[T]<8UT). In depth, the renewal time is longer ([T]<1UT) and mixtures are difficult. A numerical model was developed thanks to these coupled methods which characterize the coastal alluvial reservoir. The model was performed to become a current instrument of the site management.

Keywords