Guanajuato Groundwater Chemistry

This is the raw data used in the paper entitled \"Rising Arsenic Concentrations from Dewatering a Geothermally Influenced Aquifer in Central Mexico\" in the journal Water Research in 2020 by the authors listed here. Four files are included: 1) historical delta 18O concentrations (\"1999 18O.xlsx\") in 122 wells which were measured shortly before 1999 and assembled and reported in Jurgen Mahlknecht's PhD dissertation (Mahlknecht, J. (2003) Estimation of recharge in the Indpendence aquifer, central Mexico, by combining geochemical and groundwater flow models, University of Agricultural and Life Sciences (BOKU)); 2) historical water chemistry data (\"1999_Wells_Chemistry.xlsx\") in 246 wells which were measured shortly before 1999 and assembled and reported in Dr. Mahlknecht's dissertation; 3) water chemistry data which was collected between 2014 and 2018. Most of the wells were sampled between 2015 and 2017. Many of the wells were sampled 2-5 times during different times of the year between 2014 and 2019, however, the database included here only has the first sampled chemistry from each of the 137 wells. This was the main database used to perform the analyses in the paper; 4) water chemistry data from the 22 re-sampled wells between 1999 and 2016 (\"Resampled Well Data_mM). These only include the parameters that were analyzed in 1999. The nominal detection limit for ICP-MS data measured in 2016 was 0.01 ppb. The nominal detection limit for the Ion Chromatograph data was 0.01 ppm. Missing values indicates the data was not available. Alkalinity values are reported as mg/L \"HCO3\" which is not the convention of reporting this parameter as mg/L \"CaCO3\", however, it was consistent with the format used for the 1999 data set.