Abstract
Groundwater (GW) is the primary source of unfrozen freshwater on the planet and in many semi-arid areas, it is the only source of water available during low-water periods. In north-central Chile, there has been GW depletion as a result of semi-arid conditions and high water demand, which has unleashed major social conflicts, some due to drought and others due to agribusiness practices against the backdrop of a private water management model. The Ligua and Petorca watersheds in the Valparaíso Region were studied in order to analyze the influence of climatic and anthropogenic factors on aquifer depletion using an interdisciplinary approach that integrates hydroclimatic variables, remote sensing data techniques, and GW rights data to promote sustainable GW management. The Standardized Precipitation Index (SPI) and Normalized Difference Vegetation Index (NDVI) were calculated and the 2002–2017 land-use change was analyzed. It was shown that GW decreased significantly (in 75% of the wells) and that the hydrological drought was moderate and prolonged (longest drought in the last 36 years). The avocado-growing area in Ligua increased significantly—by 2623 ha—with respect to other agricultural areas (higher GW decrease), while in Petorca, it decreased by 128 ha. In addition, GW-rainfall correlations were low and GW rights were granted continuously despite the drought. The results confirmed that aquifer depletion was mostly influenced by human factors due to overexploitation by agriculture and a lack of water management.
Highlights
Groundwater (GW) is a very valuable resource as it accounts for 96% of the planet’s unfrozen freshwater [1]
The results demonstrate that there is a relationship between the GW decrease and the drought, it cannot be stated that there is a trend in rainfall behavior related to the significant GW
Standardized Precipitation Index (SPI) 6, a drought period between 2010 and 2015 was observed, which was more evident in SPI 12 and SPI 24, which showed a hydrological drought classified as moderate but very long
Summary
Groundwater (GW) is a very valuable resource as it accounts for 96% of the planet’s unfrozen freshwater [1]. GW use has increased significantly in recent decades and storage has decreased, with over 20% of aquifers estimated to be overexploited due to a lack of sustainable GW management [1]. This has had various impacts such as water scarcity, land subsidence, saline intrusion, and reduction of baseflow to rivers, lakes, and wetlands [1,5]. The storage decrease may be a consequence of global climate change, which affects hydrological patterns, water levels, and rainfall patterns; agricultural irrigation, land-use change, and reservoir construction can have repercussions [2,6]
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