應用三維地下水模式FEMWATER評估SRI與傳統灌溉制度之地下水補注

Applying 3D FEMWATER to Evaluate the Groundwater Recharge under SRI and Traditional Irrigation Schemes

蔡誠斌(Cheng-Bin Tsai)

指導教授 ： 陳世楷

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2014年)

https://doi.org/10.6841/NTUT.2014.00778

摘要

近年來因氣候變遷導致極端氣候事件頻繁發生，臺灣水資源之調配運用面臨極為重之挑戰，根據水利署統計農業用水佔總用水量約70%，其中又以水稻灌溉用水為主，因此傳統灌溉制度的改良顯得相當重要。目前國際上所推廣的水稻強化栽培法(The System of Rice Intensification，SRI) 以田間不湛水並提估供作物最小需水量為原則，許多研究亦指出在不影響產量下，SRI具有非常良好的節水效果。然而，長期湛水的水田具有涵養地下水的功能，因此本研究旨在探討不同灌溉制度對於淺層地下水補注效益之影響。
本研究以濁水溪沖積扇扇頂區之實驗水田區(位於彰化田中)為例，利用具有變動邊界之三維地下水模式FEMWATER模擬不同灌溉用水操作，量化比較在SRI與傳統灌溉制度(續灌、輪灌)對淺層地下水的補注效益。情境可分為SC1、SC2、SC3等三種，前兩種情境考慮有無利用有效降雨，且考慮田區底層土壤壓力水頭為為現地量值-1.2 m，SC3情境則為田間容水量-3.3 m。模擬結果顯示SC1與SC2間並無明顯差異，SC3則為導致較高之田間入滲率。以SC1模擬結果為例，續灌之平均入滲率為最高為4.04 mm/day；輪灌次之，平均入滲率為4.00 mm/day；SRI最小，平均入滲率為3.92 mm/day。SRI在補注效益上略低於國內現行制度，補注量相較於續灌及輪灌，SRI分別減少2%及4%。在田間灌溉用水量上，SRI則顯著優於續灌及輪灌，分別節省約35%及9%之田間灌溉用水量。綜合模擬分析結果，相對於補注量之減少，SRI所節省之用水量遠高於傳統灌溉制度對地下水之補注效益。研究結果可作為水利相關事業部門規劃整體水資源經營管理策略之參考。

關鍵字

傳統灌溉制度 ； SRI ； FEMWATER ； 地下水補注 ； 入滲率 ； 田間灌溉用水量

並列摘要

In recent years, the global climate change has frequently resulted in many extreme weather events in Taiwan, the water resource management and planning become a critical issue in this country. According to the WRA statistics that agricultural water occupies 70 percent of total water consumption, most of which are rice-cultivation irrigation. Therefore, improvement of the traditional irrigation schemes has become increasingly necessary. The System of Rice Intensification(SRI) has been internationally extended in recent decades, which is based on supplying crops with less irrigation water and do not continuously flood the paddy fields. Many researches also pointed out that this methodology has excellent water-saving effect without affecting rice yields. However, continuously flooding in the paddy field may be regarded as an important source for groundwater recharge. The objectives of this study was to evaluate the changes of groundwater recharge between the SRI and traditional irrigation schemes.
An experimental paddy field located in the proximal area of Choushui River alluvial fan (the largest groundwater region in Taiwan) was chosen as the study area. The three-dimensional finite element groundwater model (FEMWATER) with the variable boundary condition analog functions, was applied in simulating groundwater recharge under traditional irrigation schemes(continuous irrigation, rotational irrigation) and SRI methodology. The scenario analysis includes using effective rainfall or not (SC1, SC2), and the deep soil pressure head was set to be -1.2 m according to in-situ measurements. Soil moisture was set to be field capacity (-3.3m) in scenario SC3. The simulation results showed that there were no significant variations in SC1 and SC2, but low soil moisture in deep soil layers (SC3) will resulted in higher infiltration rate compared to SC1 and SC2. Taking the scenario SC1 as an example, the average infiltration rate for continuous irrigation, rotational irrigation, and SRI methodology were 4.04 mm/day, 4.00 mm/day and 3.92 mm/day, respectively. The groundwater recharge amount of SRI methodology was slightly lower than traditional irrigation schemes, reduced 4% and 2% compared with continuous irrigation and rotational irrigation, respectively. The field irrigation requirement amount of SRI methodology was significantly lower than traditional irrigation schemes, saving 35% and 9% compared with continuous irrigation and rotational irrigation, respectively. The SRI methodology obtained significant water-saving benefit compared to the disadvantage of reducing the groundwater recharge amount. The results could be used as a basis for the relevant government agency to formulate the integral water resource management strategies in the future.

並列關鍵字

Traditional Irrigation Schemes ； SRI ； FEMWATER ； Groundwater recharge ； Infiltration rate ； Field irrigation requirement

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