22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Bauru Aquifer System, State of Sao Paulo, Brazil: Conditioning factors of water level variations

23 Sep 2019, 16:00
1h
Trade Fairs and Congress Center (FYCMA)

Trade Fairs and Congress Center (FYCMA)

Av. de José Ortega y Gasset, 201 29006 Malaga, Spain
Poster Topic 1 - Groundwater assessment and management Poster with refreshments

Speaker

Ms Marcela Barcelos Barbosa

Description

The Bauru Aquifer System is characterized as a sedimentary aquifer, of predominantly free condition, whose recharge is associated with the direct infiltration of precipitation. This aquifer is the main source of public and private water supply in the western portion of São Paulo state, a Brazilian industrial and agricultural pole. The Bauru aquifer has been monitored as part of the Groundwater Monitoring Network, maintained and operated by the Geological Survey of Brazil. In this context, the present study contemplates the investigation and multi-thematic analysis of the intervening factors of the correlation between groundwater level response, rainfall events and anthropogenic alterations, with the purpose of increasing the knowledge of the potentiality of the Bauru aquifer system. Time series of groundwater and rainfall data were also analyzed and evaluated in order to identify the factors that could influence this relationship, such as: composition of the lithological profile above the filter in each well, thickness of the unsaturated zone, specific capacity of the well, number of production wells installed within a 5km radius, soil types and cover in the region. The time series analysis was conducted by using simple correlation between the groundwater level series to verify their similarities, and cross correlations to determine precipitation influence on the wells static level, in order to estimate the necessary time for water to infiltrate and recharge the aquifer, increasing the static level. Subsequently, the data was spatialized using ArcGIS and a multicriteria analysis was performed, assigning weights to the different variables in order to explain the time series correlations. Based on the identification of the interactions and influences of the aforementioned factors, a correlation between groundwater level and the rainfall was identified. This correlation is mainly affected by the lithological profile above the filter, the specific capacity of the wells and the number of production wells located within a radius of 5 km. Series with rapid responses to rainfall events were generally associated with essentially sandy lithographic sequences, specific capacities above 0.29 m3/h/m or with the number of production wells below 10. On the other hand, the absence of correlation or very slow response to rainfall was associated with wells whose lithographic profile had clay layers that could lead to confinement, or had a specific capacity lower than 0.29m3/h/m associated with a large number of production wells in the surroundings. Additionally, there was a significant water level decrease during a severe drought between 2013 and 2015, corresponding to the same period of the water crisis in the State of São Paulo.

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