Distribution of soil moisture and groundwater levels at patch and catchment scales

Abstract

This study is a contribution to the northern hemisphere climate processes land surface experiment (NOPEX). Its purpose is to investigate the spatial variability of groundwater levels and soil moisture content at different scales in a landscape dominated by boreal forest and till soils, which is characteristic of the Nordic countries. The analysis of data from the NOPEX area are based on a review of previous studies on the spatial distribution of these state variables and their significance for runoff formation. Soil moisture content in the unsaturated zone and depth to the groundwater table show characteristic patterns which are related to the landscape elements (patches) of the drainage basins. Similar behaviour is observed in different parts of the NOPEX region. The variability of average values between areas decreases to a minimum for catchments with size larger than 1km2. It can therefore be concluded that the main part of the spatial variability of soil moisture content and depth to the groundwater level in the till soils of the NOPEX area is found within small drainage basins. Based on a physical description of the soil, distribution functions of soil moisture content conditioned on the depth to the groundwater table have been developed, both for the patch scale and the catchment scale.