Factors Affecting Soil and Water Conservation of Terraced Paddy Fields of Shuangxi Watershed

• Main Authors: Chao-Yang Hsu, 許朝陽
• Other Authors: Shin-Kai Chen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/bhn658

碩士 === 國立臺北科技大學 === 土木工程系土木與防災碩士班（碩士在職專班） === 103 === Terraced paddy fields play a significant role in soil and water conservation in mountainous areas. Yet, detailed experimental data to confirm this function is missing, as well as an identification of the most decisive factors for infiltration, groundwater recharge and soil erosion. Therefore, the objective of this study was to quantify groundwater recharge in terraced paddies both experimentally and by related water budget method. The in-situ measurements including water requirement rate, vertical infiltration rate, soil textures, hydraulic conductivity and soil moisture of different soil layers were investigated in two experimental terraced paddy fields (there were two regions on experimental field A(FA), one was terraced paddy field at slopeland and another was set-aside land, and experimental field B(FB) was flood plain) on Gongliao District of New Taipei City. The average field infiltration rate in FA maintenance was 7.72mm/day. The under-bound percolation rate was 3-10 times as high as vertical infiltration rate. In FB, The average field infiltration rate was 11.29mm/day. The under-bound percolation rate was 4-6 times higher than vertical infiltration rate. Soil moisture analysis showed that the saturations were near 100% at inside edge of the bounds, higher than the measurements at block center, indicating that ponding water trend to percolate through inside edge of the bounds to deep soil layer. In addition, using constant head permeability test showed that the average plow sole infiltration rate was 0.09cm/day and the average non-puddled subsoil infiltration rate was 0.229cm/day. The result indicated that water was difficult vertical infiltration in plow sole layer. The amount of groundwater recharge of FA and FB were estimated as 2,849 and 3,776mm/year, account for local average annual rainfall were 53.3% and 73.3%, respectively. Recharge benefits are far more significant than for lowland paddy fields or other land uses on slope with no ponding water recorded in other studies. Finally, intergrated data to estimate the amount of field soil erosion with the Universal Soil Loss Equation (USLE), and the field soil losses in FA was 77.98ton/ha-year. If field was abandoned to become bare soil, the field soil losses will increase to 2290.68ton/ha-year. The conclusion showed that the maintenance of terraced paddy field strengthen not only sediment trapped but also soil and water conservation.