Evaluation of spatio-temporal trends of groundwater quality in different land uses using Kendall test

The monitoring of temporal and spatial variations of groundwater quality is important for better managing groundwater resources. In a heavily cultivated agricultural site, Yupori, Chuncheon (Korea), groundwater quality has been monitored since 2002 because the groundwater in this area contains elevated levels of nitrate. Concentrations of NO3-N, SO42−, and Cl− were found to be high in vegetable fields and low in fruit orchards. For groundwater management purposes, a regional Kendall test was carried out to investigate the spatio-temporal trends of three major anion (NO3−N, SO42−, and Cl−) concentrations for various land use types: vegetable fields, fruit fields, and barns. The mean concentration of NO3-N in the vegetable fields exceeded the maximum contaminant level for drinking water (10 mg L−1) and showed the highest increasing trend with time among the various land use types. The results showed a statistically significant increasing trend in the NO3-N and SO42− concentration in vegetable fields from 2002 to 2007. The estimated slope of the NO3-N and SO42− concentration in the vegetable fields was 2.1 mg L−1 per year and 1.01 mg L−1 per year over a period of 6 years. The concentration of Cl− showed an increasing tendency in fruit fields and decreasing tendency in barns. In order to regulate groundwater quality in the study area, nitrate contamination in vegetable fields should be particularly controlled. Spatio-temporal trends for different land uses using regional Kendall test can be usefully applied to control groundwater quality in the study area.