Estimating water and sediment transport through the soil at field and laboratory

Sammanfattning: Soil erosion has been widely studied by many methods as a measure of loss of soil qual-ity due to the importance of the conservation of the soil properties. However, these meth-ods produce different results that are difficult to compare. In this thesis, rain simulations with a drip infiltrometer and a revised pinhole test were used to study the soil response and to quantify sediment transport. Simulated rain events in the field generated infiltration through the upper soil profile that was directly related to the rain intensity. A tension infil-trometer was used to estimate hydraulic conductivity in the soil before and after the simu-lated rain events in the field to study the effect on the soil surface. Turbidity was measured in the water samples from drainage water in the rain events and was used as a surrogate parameter for suspended soil sediment concentration. Turbidity displayed similar pattern regarding the rain intensity applied. The pinhole test methodology was developed for un-disturbed soil samples and was amended by modifying the water content in the soil sam-ples, in order to study the response at saturation and under drainage at 40 and 100 cm ten-sion. The erosion process was studied by considering turbidity values together with out-flow rate. Sediment discharge calculations were more accurate when both these parameters included. Soil samples in the pinhole test showed similar patterns for turbidity, outflow rate and sediment discharge. However, sediment transport was lower in saturated samples than in drained samples and was highest for the samples drained at 100 cm tension. Fur-thermore, topsoil proved to be more reactive with cavities sometimes developing in the soil specimen. Our recommendation is to express the results as concentration of transported sediment (mg/mL), as these numerical values are easier to understand and compare be-tween different experiments. Regarding to the pinhole test, the recommendation is to use samples from the soil depth of interest and drained at 100 cm tension.