{"accessLevel": "public", "bureauCode": ["010:12"], "contactPoint": {"@type": "vcard:Contact", "fn": "Arizona Water Science Center", "hasEmail": "mailto:jpmacy@usgs.gov"}, "description": "This product \"Predicted nitrate and arsenic concentrations in basin-fill aquifers of the \nSouthwest Principal Aquifers study area\" is a 1:250,000-scale vector dataset and was \ndeveloped as part of a regional Southwest Principal Aquifers (SWPA) study. The study \nexamined the vulnerability of basin-fill aquifers in the southwestern United States to \nnitrate contamination and arsenic enrichment. Statistical models were developed by \nusing the random forest classifier algorithm to predict concentrations of nitrate and \narsenic across a model grid that represents local- and basin-scale measures of \nsource, aquifer susceptibility, and geochemical conditions. Separate classifiers  \nwere  developed for nitrate and arsenic because each constituent was expected to \nbe affected by a different set of factors, and each factor could have a different \nmagnitude or directional influence (increase/decrease) on concentration. For each \nconstituent, two different classifiers were developed; a prediction classifier and a \nconfirmatory classifier. The prediction classifiers were developed specifically to \npredict nitrate and arsenic concentrations in basin-fill aquifers across the SWPA \nstudy area and were based on explanatory variables representing source and \nsusceptibility conditions. These explanatory variables were available throughout \nthe entire SWPA study area and, therefore, did not pose a limitation for using the \nclassifiers to predict concentrations.\n\t\t\nThe confirmatory classifiers were developed to supplement the prediction classifiers \nin the evaluation of the conceptual model. The name, \"confirmatory,\" reflects the \nclassifier's purpose for evaluation of a-priori hypotheses and contrasts other general \ntypes of statistical models, such as those used for prediction or exploratory purposes. \nThe confirmatory classifiers included the explanatory variables used in the prediction \nclassifiers, as well as additional variables representing geochemical conditions and \nbasin groundwater budget components. The inclusion of the geochemical and basin \ngroundwater budget variables in the confirmatory classifiers allowed for further \nevaluation of the conceptual models, which was not possible with the prediction \nclassifiers alone. The geochemical data, however, were only available at specific \nwell locations, and consistent water-budget data were not available for every basin \nin the study area. The limited availability of the data for these variables constrained \nthe confirmatory classifiers to observations from 16 case-study basins and precluded \nuse of the confirmatory classifier for predicting concentrations across the SWPA \nstudy area. To contrast the scope of the two classifiers, the confirmatory classifiers \nwere developed by using all available explanatory variables but with observations \nrestricted to the 16 case-study basins, whereas the prediction classifiers were \nunrestricted with respect to spatial extent because these were developed by \nusing a subset of the explanatory variables that were available throughout the \nstudy area.", "distribution": [{"@type": "dcat:Distribution", "accessURL": "https://doi.org/10.5066/P9R2O16Y", "description": "Landing page for access to the data", "format": "XML", "mediaType": "application/http", "title": "Digital Data"}, {"@type": "dcat:Distribution", "description": "The metadata original format", "downloadURL": "https://data.usgs.gov/datacatalog/metadata/USGS.ae8e9136-9b70-4612-a184-3aebde4c922e.xml", "format": "XML", "mediaType": "text/xml", "title": "Original Metadata"}], "identifier": "http://datainventory.doi.gov/id/dataset/USGS_ae8e9136-9b70-4612-a184-3aebde4c922e", "keyword": ["Arizona", "Arsenic concentration", "Basin-fill aquifer", "California", "Colorado", "Groundwater", "Groundwater contamination", "Groundwater susceptibility", "NAWQA", "National Water-Quality Assessment Program", "Nevada", "New Mexico", "Nitrate concentration", "Southwest United States", "USGS:ae8e9136-9b70-4612-a184-3aebde4c922e", "Utah", "Water quality", "environment", "geoscientificInformation", "inlandWaters", "utilitiesCommunication"], "modified": "2020-11-17T00:00:00Z", "publisher": {"@type": "org:Organization", "name": "U.S. Geological Survey"}, "spatial": "-124.889549, 29.300033, -104.566268, 44.627454", "theme": ["geospatial"], "title": "Predicted nitrate and arsenic concentrations in basin-fill aquifers of the Southwest Principal Aquifers study area"}