The sequential percolation process from shallow to deep soil layer at sandy place
2006
Kawai, T.(Tottori Univ. (Japan)) | Kamichika, M. | Tada, Y. | Yasuda, H. | Inoue, M. | Kimura, R.
An evaluation of the percolation process in sandy soils is important because such soils are widely distributed in semi-arid regions where the agricultural potential is high. Therefore, soil water content from the surface to about l0m depth in the vadose zone was monitored for one year at the Tottori sand dune, Japan. Soil water content was measured by the ADR soil moisture sensor and precipitation was observed by the rain gauge. The precipitation events were classified into two big groups in summer and winter. And 20 snow events were observed in winter. The annual average soil water content was 7-11% in all vadose zones. The infiltration water percolated as an independent wave. This wave descended while absorbing the soil water wave that had already existed in the soil. When the water balance to 0.4m depth was calculated at two big rainfall events, the difference was within 1mm. It was determined that the surface and lateral unsaturated flow were hardly generated and vertical percolation was superior. Previous reported that the soil water moved earlier than the arrival of the percolation wave. But in this study, such a phenomenon was not observed. The descent speed of the percolation wave in winter was 2-3 times slower than in summer. Moreover, the average soil water content increased during winter. These phenomena were possibly caused by a decrease in water permeability due to the low temperature of the percolation water and soil.
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