Comparison of the modeling results of nitrate concentrations in soil water below the root zone in the local and regional scale

Abstract

The article presents a comparative analysis of the modeling results of nitrate concentrations in water below the root zone of the soil in the local and regional scale. In this research, the field-scale DNDC (Denitrification – Decomposition) and the regional-scale GROWA–DENUZ (ger. Großräumiges wasserhaushalt – Denitrifikation im durchwurzelten Boden) models were applied to the study area of the shallow aluvial aquifer of the Spodnje Savinjska dolina in the central part of Slovenia. Using the concept of Hydrological Response Unit (HRU) and Cohen Kappa statistical analysis of the degree of agreement and assessment of the reliability of the results of spatial modeling of nitrate in soil water below the root zone, we determined and interpreted the areas of maximum agreement and disagreement of model results. A good agreement was found at the highest modeled concentrations of nitrate in soil water, whereas the greatest deviations were detected primarily in the lower part of the range. The main reasons for disagreement were differences in the estimation of the denitrification conditions in the anaerobic environments of gley-soils with the shallow groundwater and differences in fertilisation scenarios and agricultural practices.