Evaporation from shallow groundwater in closed basins in the ChileanAltiplano

Abstract

The hydrological cycle in arid and semi-arid climates is highly controlled by evaporation. The correct quantification of this process is essential for improving the accuracy of water balance estimates, especially in closed basins. The objective of this paper is to characterize evaporation rates from shallow groundwater using the chamber approach in six closed basins in the Altiplano of northern Chile. Measurements were made at 49 locations with water-table depths ranging from 0.09 m to 3.3 m. Estimated daily evaporation rates appeared to be strongly related to groundwater depth and soil texture. In particular, the highest rates were recorded in areas with high groundwater tables and coarse-grained soils. Evaporation curves were derived by fitting exponential and power relationships as functions of the groundwater depths that we proposed to use in the study area. An application of these curves for the Salar de Pedernales basin produced an estimated evaporation flow of 530 L s -1 , using the average curve.Key words evaporation chamber; closed basins; shallow groundwater; Altiplano; Chile Evaporation d'eaux souterraines peu profoundes dans des bassins endoreiques de I'Altiplano Chilien Résumé Le cycle hydrologique dans les régions à climats aride et semi-aride est fortement contrôlé par l'évaporation. Une quantification correcte de ce processus est essentielle pour améliorer la précision des estimations des bilans hydrologiques, particulièrement dans les bassins endoréiques. Le but de cette étude est de caractériser le taux d'évaporation des eaux souterraines peu profondes, en utilisant la méthode de la chambre d'évaporation dans six bassins endoréiques de l'Altiplano du nord du Chili. Des mesures ont été effectuées en 49 points distincts, pour des profondeurs de nappe allant de 0.09 à 3.3 m. Il apparaît que le taux d'évaporation journalier est fortement lié à la profondeur de la nappe et à la texture du sol. En particulier les taux les plus élevés ont été mesurés dans les zones où la nappe est peu profonde et où la texture du sol est grossière. Des courbes d'évaporation ont été déduites par ajustement de fonctions exponentielles et puissance de la profondeur de nappe. Le taux d'évaporation donné par l'application de ces courbes au bassin du Salar de Pedernales est estimé à 530 L s -1 , en utilisant la courbe moyenne.

A variable source area for groundwater evapotranspiration: impacts on modeling stream flow

“…Therefore, a larger diel range in baseflow during periods of higher water table is consistent with a conceptual model that implies a larger impact of ET when the groundwater table is closer to the ground surface. As indicated by Johnson et al (), the highest rates of ET are found where groundwater tables are shallow and soils have a coarse texture. Finally, the absence of losing reaches rules out the likelihood that temperature‐mediated increases in daytime infiltration (Constantz, ) contributed to the diel baseflow signal.…”

Modelling evaporation processes in soils from the Huasco salt flat basin, Chile

“…In closed Altiplano basins such as those encountered in arid and hyper arid basins in the northern Chile, evaporation is the main source of aquifer depletion, and thus its study is crucial for water resources management. Understanding evaporation is also important for the study of sensitive soil systems such as wetlands (de la Fuente and Niño, ; Johnson et al, ). Nonetheless, understanding the evaporation processes in these environments is complex because evaporation occurs under non‐isothermal conditions, where water can be mobilized as liquid water or water vapour (Nassar and Horton, ; Grifoll et al, ; Hernández‐López et al, ).…”

Groundwater Origins and Circulation Patterns Based on Isotopes in Challapampa Aquifer, Bolivia

“…Hence, the most depleted isotopic values in groundwater would represent recharge at higher altitudes. Conversely, water retained in the surface and shallow aquifers are significantly affected by evaporation [10,30]. As a consequence, the most enriched isotopic compositions are expected in samples of the aforementioned sites.…”