Types: Master thesis
Subjects: hydrology, China, soil moisture variability, N2O emission, hillslope hydrology, :Mathematics and natural science: 400::Geosciences: 450::Hydrology: 454 [VDP], Vadose zone flowpaths
Forested catchments in subtropical southwest China are important sites for nitrogen, primarily due to denitrification. Denitrification depends strongly on soil moisture content and the residence time of soil water. Both depend on the hydrological properties of the soils. In this study we investigated the soil hydrological properties and water flow paths on a hill slope in the TieShanPing catchment around 25 kilometres north-east of Chongqing. Soils were sampled for analyses of water retention characteristics, grain size distribution, hydraulic conductivity, porosity and bulk density. In addition, TDR-generated soil moisture data were analysed with respect to volumetric water flow in response to precipitation events. A dye tracer experiment was also conducted for visual support of analyses. Hydraulic conductivity and chemical data support the hypothesis that episodic rain water does not generate overland flow, and TDR measurements support the hypothesis that episodic rain water mainly infiltrates through the upper 15-20 cm of the soil, due to a combination of functional saturation of the B1 horizon and subsequent infiltration excess. With an annual runoff coefficient of only 22 %, and accounting for an evapotranspiration of up to 60 %, there is still a deficiency in the water budget of at least 18 % which may indicate that a not insignificant amount of water percolates to deep groundwater and is lost from the sub-catchment. In future efforts, it will be important to ensure that the placement of soil moisture sensors is representative of the entire system to be described. Other sampling, including water samples for chemical analyses, discharge readings and ground water level readings, should be automatic and be set to high sampling frequencies during episodes.
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