Chemistry and isotopic data from ground water and surface water in the southern Española Basin and Santa Fe embayment were compiled from existing sources, and supplemented with data obtained from new sampling events in 2005. Existing records from the City and County of Santa Fe, the New Mexico Office of the State Engineer (NMOSE), the New Mexico Environment Department (NMED), the U.S. Geological Survey (USGS), the Metropolitan Water Board, and libraries of private consultants provide baseline chemistry data spanning 50 years and over 300 locations. In 2005, ground water from 50 new sample locations was analyzed for major and minor ion and trace element chemistry (38 elements), oxygen-18 and deuterium, and field measurements of specific conductance, dissolved oxygen, pH and temperature. The data are derived from wells, streams and springs, including municipal, commercial, and private domestic wells, and the NMOSE multi-level piezometers. The large size and mixed origin of the data set present data
quality challenges. Quality control filters provide a high degree of confidence in the precision of the data, but temporal inconsistencies are inherent in the data set.