水田開裂及田埂特性對入滲之探討

本文探討水田受日曬開裂及田埂透水性對入滲及補注地下水之影響，藉由彰化田中示範田區之灌溉水量，土壤物理特性及水力傳導係數之量測數據，作爲三維地下水數値模式FEMWATER模擬水田田區不同乾裂程度及田埂水力傳導係數之地下水入滲，側流及推估地下水有效補注量。利用田中地區土層組合，以FEMWATER模式模擬在乾濕邊界土壤壓力水頭乾田爲-3.3m及-6.9m對應濕田為-1.2m情況下之入滲，由模擬結果顯示乾田時期之水田田面開裂，裂縫穿過牛踏層之後，具有強大之入滲能力，裂縫深度爲80cm、60cm及27.5cm之入滲通量分別爲裂縫深度20cm者之18.77、14.50及8.06倍，在田面開裂造成牛踏層破壞後，方能使模擬之入滲率達到與乾田區現地入滲試驗較為接近之結果。由田埂模式模擬得知，當田埂兩邊分別爲水田區與乾田區，水田區單日之總垂直入滲量與田埂單日之側滲總量相差10倍。而位於兩水田間田埂之埂間滲漏率約爲水田垂直入滲率之兩倍。由模擬成果可瞭解水田入滲至地下水之移動機制，垂直流與水平側向流動過程，並可提供研擬地下水補注之所需。

關鍵字

入滲；水田；開裂；田埂；模擬

並列摘要

The study investigates the soil crack caused by intensive sun light and bound characteristics on the infiltration in paddy field. A three dimensional ground water model FEMWATER is adopted to simulate the vertical and lateral water movement in the paddy field subjected to various crack conditions and hydraulic conductivities of bund. Using the field and laboratory data of irrigation water requirements, soil physical properties, hydraulic conductivities and soil profiles obtained from Ten-Chung, FEMWATER simulates the water movement at dry/wet paddy boundary where the pressure head in the dry paddy are set to be -3.3 m and -6.9 m, and the pressure head in wet paddy is set to be -1.2 m. Simulation results show that if the cracks develop extensively and penetrate the plows sole, the infiltration rate may increase significantly. The infiltration fluxs of crack with depths of 80, 60, and 27.5 cm are 18.77, 14.50, and 8.06 times higher than that of 20 cm, respectively. The vertical percolation rate is 10 times higher than the lateral seepage rate at the dry/wet bund boundary while the vertical percolation rate is 2 times higher than the lateral seepage rate at the wet/wet boundary in the paddy. The research results can elucide the mechanisms of water movement from paddy field and the processes of vertical percolation and lateral seepage under various environmental conditions in the unsaturated region.

並列關鍵字

Infiltration ； Paddy ； Crack ； Bund ； Simulation

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