Water and Construction - Hydrogeology: Objectives, Methods, Applications - page 240

alluvial deposits led to a rapid acceleration of erosion by the river, and
consequently, to a signifi cant lowering of the water table in its accompanying
aquifer, particularly between 1965 and 1978. Upstream of a catchment fi eld
for the city of Nice, where the water table reached the surface in 1965, the
level dropped by 8 meters in 1967. This evolution continued, leading to the
drying of 370 agricultural wells and seriously endangering the productivity
of potable water catchments. Limitations on gravel mining in the active
riverbed were very progressive, and conservation measures were put into
effect as early as 1971. These consisted of 10 overfl ow dams with waterfall
heights of 4 to 6 meters, built transversally across the river, and intended
to stop the aforementioned harmful effects and to reestablish the river's
waterline. These mechanisms, although they did, indeed, stabilize the Var's
erosion rates and the dropping water table, also modifi ed the solid particle
transport conditions of the river, increasing erosion in certain areas due to
lack of deposition, and decreasing the infl ow to the aquifer from the river
in other areas, due to sedimentation and clogging of its bed and its banks
(Thévenin, 1983).