GROUNDWATER NITRATE CONCENTRATION AND ITS RELATION TO LAND COVER AND WATER DEPTH IN BUNCOMBE COUNTY

High concentrations of nitrate in groundwater can be harmful to human health if ingested, and may be the primary cause of blue baby syndrome, among other health impacts. In this study, the spatial distribution of nitrate in groundwater for 610 private drinking water wells in Buncombe County, North Carolina was modeled. While nitrate concentration in the sampled wells did not exceed the 10mg/L limit established by the United States Environmental Protection Agency, some wells had nitrate concentrations approaching this limit (as high as 8.5mg/L). Kriging interpolation was implemented within a geographic information system to predict nitrate concentrations across the county, and a co-kriging model using land cover type and depth to water table as covariates was developed. Cross validation statistics of root mean square and root mean square standardized for both models were compared and the results showed that the predicted nitrate layer was improved when land cover layer were integrated into the model. The co-kriging interpolated surface with landcover as covariate had the lowest root mean square (0.979) when compared to the kriging interpolated surface (0.986), indicating a better fit for the co-kriging surface with landcover. The addition of depth to water table layer as covariate did not improve the co-kriging surface. High nitrate value of 2mg/L and above were concentrated in Hay/Pasture land, developed open space and deciduous forest containing 37.14%, 34.29% and 28.57% of the high nitrate concentration respectively. Results indicated that land cover type have an impact on nitrate concentrations in groundwater and the hay/pasture land cover type, in particular, contained the highest nitrate concentrations within the county.