| Summary: | 碩士 === 國立屏東科技大學 === 土木工程技術研究所 === 86 === For the government attending the World Trade Organization (WTO), the rice yield and the area of paddy fields will be obligated to decrease. However,considering the functions of groundwater conservation and recharge by paddy fields, it shall still maintain the ecological function to insure the sustainable
use of groundwater while the productive functions of paddy fields are suspended.The motivation of my research is trying to understand the phenomenon of soil water movement and groundwater recharge in paddy fields after irrigating.
To achieve the purpose, my research will be divided into three parts: (1) field experiments (2) analysis of soil characteristic (3) numerical simulation.The field experiments is setting up on a 5m×5m paddy field, and excavate a ditch of 1.3m depth. In order to measure the shallow groundwater table, there are setting three observed wells in this field. There are two types of field test, fixed-head and variated-head, use to measure the average infiltration rate on the paddy field. Each test proceed with three different ponding depth, 10cm, 15cm, 20cm. The result of this field experiment demonstrate that the shallow groundwater table and average infiltration rate are in proportion to the ponding depth.In this research three sets of soil samples are taken from the field to do the soil characteristics analysis. The result of the analysis shows that the sections of the interesting region can be classified into three different types of soil which are silty loam, loamy sand and sand respectively. The study also complete the following soil characteristics analysis, the soil classify,soil bulk density,saturated hydraulic conductivity, the curve of relation between pressure head and water content, the curve of relation between pressure head and relative hydraulic conductivity, and the curve of relation between pressure head and water capacity. The research adopts FEMWATER numerical model and the software GMS , which has a graphic interface as a platform of input and
output data, to simulate the shallow groundwater table of experiment region.
A 2-D conceptual model will be built first, then using boreholes data to accom plish a 3-D conceptual model. The set up of boundary conditions are based on the field experiment measurements. The model are calibrated by adjusting the flux of Cauchy boundary with error tolerance equal to ±10%. The result shows th at the water table based on whole time period is closed to the one based on the step by step time period. Key words : Soil Water Movement, Paddy Field, Field Experiment, Numerical Model.
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