Geostatical Methods For Mapping Groundwater Nitrate Concentrations
Mevlut UYAN, Tayfun CAY
The purpose of this study is to evaluate the spatial changes of groundwater nitrate concentrations by using geostatistical methods based on data from 119 groundwater wells. Geostatistical methods have been used widely as a convenient tool to make decision on the management of behavior of hydrochemical parameters in groundwater.
To evaluate the spatial changes nitrate concentrations in groundwater, GIS is used for the application of universal kriging method with cross-validation leading to the estimation of groundwater nitrate concentrations. Nitrate concentrations followed a log-normal distribution and demonstrated a moderate spatial dependence according to the nugget ratio (60%).
The experimental variogram of groundwater nitrate concentrations was best-fitted by a spherical model. Cross-validation errors are within an acceptable level. According to spatial distribution map, nitrate pollution in the groundwater occurred most in the center of the city because of nitrate excess from wastewater in industrial production.
Key Words : Geostatistics, Universal kriging, Groundwater nitrate content, Geographic Information System (GIS)