The drawdown in the nucleus led to a reduction of 94% of the evaporation flow that characterized the natural regime, resulting in an impact of 0.15 m3·s−1 in the water balance. The evaporation rate in the mixing zone, in both periods, reached values of 5.84 mm·d−1 in the lakes and values <0.5 mm·d−1 in areas near the nucleus and the alluvial fans where the thickness of the unsaturated zone increases. Considering the total area covered by the free water surface in the Salar de Atacama basin, an average evaporation flow of 0.24 m3·s−1 was obtained for the lakes. This value remained almost constant between both dates because the evaporation rate and the extension area covered by lakes remained almost constant. In the northern mixing zone, where the water table depth was fairly constant between 1986 and 2018, evaporation rates overall remained quite similar. In the eastern and southeastern mixing zones, the evaporation rate also remained constant in the EMZ and MMZ areas, but in the IMZ area, especially towards the nucleus side of this sub-zone, the slight drawdown of the water table caused a reduction in the evaporation rate. In percentage, the mixing zone experienced a minor reduction (13%) in the discharge flow than the nucleus, but this was enough to cause an impact in the evaporation flow of 1.67 m3·s−1, which was higher than the produced in the nucleus. Finally, the alluvial zone scarcely contributed to the water balance in 1986 and 2018 because the depth of the water table was always deeper than 2 m. When the total evaporation discharge estimated for the year 1986, 12.85 m3·s−1, is compared with the evaporation flow calculated for the year 2018, 10.95 m3·s−1, a reduction of 1.90 m3·s−1, equivalent to 15%, is evidenced. The authors would like to apologise for any inconvenience caused.

Peer reviewed