Analysis of subsurface temperature data to quantify groundwater recharge rates in a closed Altiplano basin, northern Chile

Kikuchi, C. P.; Ferré, T. P. A.

Analysis of subsurface temperature data to quantify groundwater recharge rates in a closed Altiplano basin, northern Chile | Analyse de données de température de subsurface pour quantifier les taux de recharge d’un bassin fermé de l’Altiplano, Nord du Chili Análisis de los datos de temperatura subsuperficial para cuantificar las tasas de recarga del agua subterránea en una cuenca cerrada del Altiplano, norte de Chile 分析地表以下温度资料以量化智利北部封闭的Altiplano盆地地下水补给量 Análise de dados de temperatura subsuperficial para quantificar as taxas de recarga das águas subterrâneas em uma bacia fechada do Altiplano, Norte do Chile

2017

Kikuchi, C. P. | Ferré, T. P. A.

Quantifying groundwater recharge is a fundamental part of groundwater resource assessment and management, and is requisite to determining the safe yield of an aquifer. Natural groundwater recharge in arid and semi-arid regions comprises several mechanisms: in-place, mountain-front, and mountain-block recharge. A field study was undertaken in a high-plain basin in the Altiplano region of northern Chile to quantify the magnitude of in-place and mountain-front recharge. Water fluxes corresponding to both recharge mechanisms were calculated using heat as a natural tracer. To quantify in-place recharge, time-series temperature data in cased boreholes were collected, and the annual fluctuation at multiple depths analyzed to infer the water flux through the unsaturated zone. To quantify mountain-front recharge, time-series temperature data were collected in perennial and ephemeral stream channels. Streambed thermographs were analyzed to determine the onset and duration of flow in ephemeral channels, and the vertical water fluxes into both perennial and ephemeral channels. The point flux estimates in streambeds and the unsaturated zone were upscaled to channel and basin-floor areas to provide comparative estimates of the range of volumetric recharge rates corresponding to each recharge mechanism. The results of this study show that mountain-front recharge is substantially more important than in-place recharge in this basin. The results further demonstrate the worth of time-series subsurface temperature data to characterize both in-place and mountain-front recharge processes.

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