Recharge controls in arid and hyperarid piedmont - Example of the Pampa del Tamarugal basin, Northern Chile.
Abstract ID#: 35542
The endorheic Pampa del Tamarugal basin (Northern Chile) is shaped in by a Central Depression (Northern extension of Atacama Desert). This depression contains the Pampa del Tamarugal lowland (1000 m a.s.l) and the Andean Piedmont, limited on his eastern side by the Precordillera mountain range (5000 m a.s.l). This area is one of the most arid areas of the world. The climatic context is arid and hyperarid, with an annual average precipitation close to 250 mm.y-1 in the Precordillera and no precipitations in the lowland. This lowland contains the Pampa del Tamarugal regional aquifer, which is a strategic groundwater resource for the Northern Chile as a whole.
The study of water transfers from the Precordillera to the downstream aquifer highlights several geomorphological and geological controls on the recharge. This recharge also depends on climatic control such as El Nino/La Nina Southern Oscillations.
The geological and geomorphological settings of the piedmont area, such as the spatial distribution of aquifer geological layers and the outcropping of bedrock (acting as impermeable barriers), control the groundwater circulations and suggest preferential recharge locations in the piedmont. On this basis, it is shown that most of the potential recharge should occur during flooding, when high altitude precipitations generate surface runoff that reaches the downstream aquifer recharge zone. Based on the estimation of the flooded area surface, we attempt quantifying the recharge of aquifer in lowland area when flashflood occurs. Numerical modelling accounting for pedotransfer functions (based on in situ sampling) with Hydrus-1D is performed to quantify this transient recharge as a function of various flooding duration.