Characterizing Aquifers - Hydrogeology: Objectives, Methods, Applications - page 141

Figure 76 Marine or evaporite origins of water in the Souss aquifer (Maroc).
b) Example of the lower Var valley (Guglielmi & Mudry, 1996)
The alluvial aquifer in the lower Var valley can be fed by the infi ltration of
river water and by discharge from aquifers in the contiguous hillsides. The
chemical characteristics of the two types of water are clearly differentiated:
the Var river, which drains the Triassic (gypsiferous) bases of subalpine
overthrusts, has a high sulfate content (150 to 200 mg·L -1 , compared to 0
to 20 mg·L -1 for hillside aquifers). The Pliocene puddingstone of the hills,
rich in bedrock silicates, gives water a high silica content (15 to 30 mg·L -1 ,
compared to 5 to 7 mg·L -1 for Var water). A simple mixture of the two-
component model (aquifer fl ux = Var fl ux + Pliocene fl ux) allows both the
evaluation of infl ows at a given point over time, and the mapping of each
environment zone of contribution (Figure 77).
The Var's high precipitation zones (headwaters, middle segment) have
a piezometry diverging downstream, corroborating this recharge. The zones
of high hillside contribution have a piezometry converging towards the
river, confi rming that the hills drain to the river.