水田入滲水力特性之試驗研究

水田灌溉因長時間保持田面湛水狀態，爲涵養地下水之重要來源。本研究利用位於田中之實驗水田區進行現地試驗以探討水田之入滲水力特性。現場試驗包括土壤取樣、水田土壤剖面水份含量及基本入滲率之測定、決定牛踏層之厚度及其飽和水力傳導係數，並評估增加水田入滲量之各種方法。藉由微型張力計及雙環入滲計之量測結果顯示牛踏層位置介於翻耕過泥濘層（厚約20公分）與底層非翻耕層之間。厚度約爲7.5公分，飽和水力傳導係數介於0.034～0.083cm／day。入滲垂向水流在牛踏層以下發展成為重力／非飽和流，而底層土壤之滲透性較佳，各土層飽和水力傳導係數約為牛踏層之20～30倍。現地實驗另顯示增加湛水深（10公分）及打破牛踏層分別可使入滲率增加1.47倍及3.68倍。本研究所得之土壤特性資料若能配合驗證數學模式將能進一步瞭解水田入滲機制並提供較爲精確之資訊協助水利單位進行水田地下水補注量之推估。

關鍵字

入滲；水田；牛踏層；水力傳導係數

並列摘要

Since the paddy field has long term ponded with water, it becomes one of the major sources for groundwater recharge. The object of the study is to investigate the hydraulic characteristics of infiltration in paddy field. Field experiments are conducted in Ten-Chung flooded paddy field. The experiments include the soil sample analysis, the measurement of soil water content /infiltration rate, the determination of saturated hydraulic conductivity for the least permeable layer (hard pan), and assessing the methods for increasing the infiltration rate. By using the mini-tensionmeters and double-ring infiltration meter, the experimental results indicate that the least permeable layer is positioned at the interface of puddled topsoil and non-puddled subsoil, and the average thickness of this layer is 7.5 cm with the saturated hydraulic conductivity ranging from 0.034 to 0.083 cm/ day. The vertically infiltrated flow is under saturated condition within the hard pan layer and becomes unsaturated in the subsoil below the hard pan layer. The hydraulic conductivity of the subsoil is 20~30 times more permeable than the hard pan layer. In-situ measurements also show that the breakage of hard pan is the effective me to increase the infiltration rate by 3.68 times. Raise of ponded water level can only increase the infiltration rate by 1.47 times. The experimental data obtained from this study can be used to the numerical simulation which will help us to understand the detailed infiltration mechanisms and to accurately estimate the amount of groundwater recharge in paddy field.

並列關鍵字

Infiltration ； Paddy field ； Hard pan ； Hydraulic conductivity

主題瀏覽