Abstract
The SISE-Eaux database of water intended for human consumption, archived by the French Regional Health Agency (ARS) since 1990, is a rich source of information. However, more or less regular monitoring over almost 30 years and the multiplication of parameters lead to a sparse matrix (observations × parameters) and a large dimension of the hyperspace of data. These characteristics make it difficult to exploit this database for a synthetic mapping of water quality, and to identify of the processes responsible for its diversity in a complex geological context and anthropized environment. A 10-year period (2006–2016) was selected from the Provence-Alpes- Côte d’Azur region database (PACA, southeastern France). We extracted 5,295 water samples, each with 15 parameters. A treatment by principal component analysis (PCA) followed with orthomax rotation allows for identifying and ranking six principal components (PCs) totaling 75% of the initial information. The association of the parameters with the principal components, and the regional distribution of the PCs make it possible to identify water-rock interactions, bacteriological contamination, redox processes and arsenic occurrence as the main sources of variability. However, the results also highlight a decrease of useful information, a constraint linked to the vast size and diversity of the study area. The development of a relevant tool for the protecting and managing of water resources will require identifying of subsets based on functional landscape units or the grouping of groundwater bodies.
Highlights
Groundwater conveys information acquired during its journey from the surface to the aquifer [1].Its composition reflects the inputs from the atmosphere, and the interactions with the vegetation cover, presence of agricultural or industrial activities, characteristics of the soil through which it percolated, and lithology of the geological formations that shelter the aquifers [2,3,4,5,6,7,8,9]
In France, health monitoring of the water quality intended for human consumption is carried out by Health Regional Agencies (Agence Régionale de la Santé or ARS)
PC2 relates to calcareous and karst areas, whereas with PC3 we find other contaminated environments, and in particular the coastal plains
Summary
Groundwater conveys information acquired during its journey from the surface to the aquifer [1].Its composition reflects the inputs from the atmosphere, and the interactions with the vegetation cover, presence of agricultural or industrial activities, characteristics of the soil through which it percolated, and lithology of the geological formations that shelter the aquifers [2,3,4,5,6,7,8,9]. The chemical and bacteriological composition of the water is a source of information that can help characterize different landscape units and the impact of human and industrial activities [10]. Over 32,000 catchments are monitored, distributed as 96% and 4% of groundwater and surface water, respectively The results of this monitoring are archived in a database named SISE-Eaux, containing data of various nature, namely physico-chemistry, composition in major ions, microbiological parameters of fecal or non-fecal origin, heavy metals, etc. This water quality database has been continuously supplied since 1990 and has been in a digitized format for computers for more than 15 years
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