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

• Main Authors: Cheng-Bin Tsai, 蔡誠斌
• Other Authors: Shih-Kai Chen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/p2hgh3

碩士 === 國立臺北科技大學 === 土木與防災研究所 === 102 === 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.