• Journal of the Korean Society of Groundwater Environment
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• v.2 no.2
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• pp.58-63
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• 1995

Cokriging was applied for the estimation of the water levels of the basal leachate and the surrounding groundwater at the Nanjido waste landfill area. When the groundwater level is estimated at the high relief area, it makes a good result to use the data of groundwater level and elevation simultaneously because groundwater level is correlated with topography. This study determined the best semivariogram model of 87 groundwater levels and 144 elevations through cross validation test, and produced the contour maps of groundwater levels using ordinary kriging and universal kiging. Two contour maps don't make big difference at the waste site because this area has a large number of groundwater level data. However, they show big difference at the upper left part of the study area because this area has high relief and a small number of sample data. Their difference is also found at the south area near the Han river. When the topography is considered for the both areas, the contour map of cokriging is thought to be closer to the real groundwater distribution than that of kriging.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.555-563
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• 2016

Uniformity and leveled distributions of soil chemicals across paddy fields are critical to manage optimal crop yields, reduce environmental risks and efficiently use water in rice cultivation. In this study, an investigation of spatial distributions on soil chemical properties was conducted to evaluate the effect of land leveling on mitigation of soil chemical property heterogeneity from a remodeled paddy field. The spatial variabilities of chemical properties were analyzed by geostatistical analyses; semivariograms and kriged simulations. The soil samples were taken from a 1 ha paddy field before and after land leveling with sufficient water. The study site was located at Bon-ri site of Dalseong and river sediments were dredged from Nakdong river basins. The sediments were buried into the paddy field after 50 cm of top soils at the paddy field were removed. The top soils were recovered after the sediments were piled up. In order to obtain the most accurate spatial field information, the soil samples were taken at every 5 m by 5 m grid point and total number of samples was 100 before and after land leveling with sufficient water. Soil pH increased from 6.59 to 6.85. Geostatistical analyses showed that chemical distributions had a high spatial dependence within a paddy field. The parameters of semivariogram analysis showed similar trends across the properties except pH comparing results from before and after land leveling. These properties had smaller "sill" values and greater "range" values after land leveling than ones from before land leveling. These results can be interpreted as land leveling induced more homogeneous distributions of soil chemical properties. The homogeneous distributions were confirmed by kriged simulations and distribution maps. As a conclusion, land leveling with sufficient water may induce better managements of fertilizer and water use in rice cultivation at disturbed paddy fields.