Using multiple-variable indicator kriging for evaluating water quality from private household wells in Gaston County, NC

Authors: Claudio Owusu*, Department of Geography and Earth Sciences and Center for Applied Geographic Information Science, University of North Carolina, Charlotte NC 28223, Samantha Dye, Gaston County Department of Health & Human Services, Gastonia, NC 28052, Wenwu Tang, Department of Geography and Earth Sciences and Center for Applied Geographic Information Science, University of North Carolina, Charlotte NC 28223, Eric Delmelle, Department of Geography and Earth Sciences and Center for Applied Geographic Information Science, University of North Carolina, Charlotte NC 28223
Topics: Medical and Health Geography, Water Resources and Hydrology, Spatial Analysis & Modeling
Keywords: Household wells, Water quality, Monitoring, Contaminants, Risk, Kriging
Session Type: Paper
Day: 4/4/2019
Start / End Time: 5:00 PM / 6:40 PM
Room: Balcony A, Marriott, Mezzanine Level
Presentation File: No File Uploaded


Monitoring water quality from private household wells faces challenges due to low routine testing which is unregulated under the Safe Drinking Water Act, and limited knowledge of treatment options from well-owners. These challenges are exacerbated by the presence of contaminants which can be used as indicators of the water quality. These contaminants are mainly microorganisms, disinfectants, radionuclides, inorganic, and organic chemicals. Since different contaminants can occur naturally in the soil and other environmental factors can also aid in their transport to the sourced groundwater, assessing household water quality can be complex. The purpose of this study is to evaluate commonly known contaminants from private household wells in Gaston County using multiple-variable indicator kriging, a geostatistical approach, to delineate the spatial distribution of water quality. The maps of the spatial distribution indicate regions with water quality issues according to the national maximum contaminant levels (MCLs) for drinking water in the United States. The data was obtained from the North Carolina State Laboratory of Public Health on 1,239 private wells results from 2011 to 2017 in Gaston County, NC. This study focused on a series of contaminants with at least 20 lab results exceeding the MCLs. Finally, risk regions were probabilistically delineated, and their accuracy was gauged using a cross-validation procedure based on the observed data. The approach is portable to other regions facing similar issues of low routine testing, and the functionality can further be embedded into a real-time surveillance system for monitoring water quality from private household wells.

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