Abstract
Abstract Groundwater is an essential resource for society and the environment in Brazil. More than 557 m3/s (17.5 km3/y) are extracted through 2.5 million wells to meet demand in cities and the countryside, generating an economy of R$ 56 billion per year (US$ 14 billion/year). The aquifer has a remarkable function in the hydrological cycle because its large storage regulates the perenniality of rivers, lakes and preserves mangroves, marshes, and vegetation in dry periods. Aquifer discharges maintain between 24% (annual average) and 49% (dry season) of the flow of these surface water bodies. Although studies on groundwater quality are still restricted, it is known that most aquifers still preserve their excellent natural quality. Nevertheless, over the past years, there has been a growing increase in cases of contamination associated with: (i) natural geochemical anomalies (iron, manganese, and fluorine, secondarily, chromium, and barium, and rarely arsenic) due to the dissolution of specific minerals; and (ii) human contaminant activities, related to urban areas without sewage network, or with industrial activities, storage of hazardous products, and solid waste facilities. Among the anthropic compounds commonly handled, the most problematic are the chlorinated organic solvents and heavy metals, and in non-sewage areas, nitrate. The precarious knowledge of aquifer-quality, especially in cities, demonstrates the need to invest in regular and systematic hydrogeological research and mapping projects that drive to the improvement of the practices on aquifer quality protection.
Highlights
Groundwater is a valuable water resource for both public and private supply in Brazil
The aquifer has a remarkable function in the hydrological cycle because its large storage regulates the perenniality of rivers, lakes and preserves mangroves, marshes, and vegetation in dry periods
With groundwater extractions over 557 m3/s (17.5 km3/y), through more than 2.5 million tubular wells, this resource is fundamental for the economy, and population health, whether in the countryside or cities (Hirata et al, 2019)
Summary
Groundwater is a valuable water resource for both public and private supply in Brazil. Aquifers are large reservoirs, where more than 90% of all water naturally stored in the country is found Due to this large storage, its extraction is very little affected by long drought periods, which allows balancing the water supply in cities and countryside. This study presents a critical evaluation of the water quality situation in Brazilian aquifers and its relation with natural and anthropic contamination, it is recognized that there are occurrences: (i) induced by the lack of control in groundwater extractions, which brings intrusion of saline or low-quality water to the aquifer; and (ii) associated with poor design, construction and/or maintenance of supply wells
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