Exploring water for human consumption in rural and urban areas in low suitable hydrogeological environments

FÁTIMA NOELIA BÉCHER QUINODÓZ; MÓNICA BLARASIN; A. CABRERA.; GIULIANO ALBO, MARÍA JESICA; MATTEODA EDEL; L. MALDONADO

Rendiconti Online della Società Geologica Italiana

Società Geologica Italiana

Lugar: Roma; Año: 2016 vol. 39 p. 31 - 31

2035-8008

For decades, small towns and rural people, located in the area with the most salinized unconfined aquifer of the South of Cordoba province (Argentina), have had serious problems to supply appropriate water for different activities. The lack of appropriate groundwater is linked to the presence of high values of total dissolved salts (TDS), Arsenic (As) and Fluoride (F) which are part of the natural baseline chemical quality and influenced by the climate and the regional geological setting. Furthermore, indicators of the impact of urban and agricultural activities were detected, such as high amounts of nitrates (up to 1,000 mg/L), pathogenic organisms (E. coli) and occasionally atrazine and caffeine. The objective of this work is to show classical geological, geomorphological, geophysical and hydrogeological studies that have led to the identification of local suitable areas for groundwater abstraction in this challenging region. The study area, which is characterized as mainly aggradational, is a slightly undulating plain that presents two geomorphologic environments: a) Eolian, which is formed by old longitudinal dunes, with modern reactivations that produced parabolic dunes. b) Fluvio-eolian, which presents overlapping of eolian deposits and sediments associated to paleoalluvial fans of the Quinto River. The study has finally showed a complex hydrogeochemical pattern, resulting especially from the strong influence of lithological and topographical features. In active sand dunes or hills where local flow systems have developed (recently recharged by rainwater) groundwater is fresh (0.7 g/L - 1.5 g/L) and sodium bicarbonate type. In the rest of the plain, brackish and salty water (1.6 g/L - 10 g/L), of sodium sulfate or sodium chloride type, is mainly the result of the evolution along regional groundwater flows. The multivariate statistical analysis in Q Mode made it possible to validate the relationship between the groundwater quality and the topography, and R Mode, to identify groups that separate fresh water from salt water and the connection of As and F with more alkaline waters and high pH. The geophysical results have allowed us to estimate the total depth of the freshwater lenses (up to 20 m). Also, the annual aquifer recharge (R) from rainfalls (P) was estimated with the water table fluctuation method, being R the 10 per cent of P. Finally the available fresh water volume was calculated. The results were later adopted by different rural and urban users.