Completation of time series of water table levels in a flatland area of the Buenos Aires province

Abstract

The objective is to complete temporary records of shallow water tables in a depressed sector belonging to the Azul river basin (province of Buenos Aires), within the framework of a groundwater mathematical modelling. The completed records make up the upstream boundary condition of the fluxes in the domain. Different time series were considered to correlate them with the water table levels: a) accumulated precipitation anomalies, b) gravimetric anomalies (GRACE satellite mission) and c) accumulated hydrological anomalies (difference between precipitation and potential evapotranspiration). From the six wells selected for the analysis and for the period where the series have completed records (Oct 2014-Apr 2016) it can be deduced that the precipitation anomalies (a) present the lowest correlation coefficients r and it was discarded as analog series. The monthly gravimetric anomalies (b), Gravity Recovery and Climate Experiment (GRACE) joint mission of NASA and the German Aerospace Center (DLR) showed good correlations, with values of r ranged between 0.624 and 0.798, although the series support has been discontinued since 2017. The accumulated hydrological anomalies, which were calculated on a daily scale and lagged with respect to the water levels by a weekly lag to improve the regressions, presented very good correlations, with rranged between 0.861 and 0.894, and were selected as an analog completion series. Considering the better availability of climatic data compared to satellite data and good results achieved, the use of this methodology is recommended in sectors with shallow groundwater levels where the evaporation process can be considered an important hydrological component.