Author(s): Asari Takada; Kazuaki Hiramatsu; Ngoc Anh Trieu; Masayoshi Harada; Toshinori Tabata
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Keywords: Rainfall-runoff analysis; Kinematic wave model; Rainfall change; Land use change; Vietnam
Abstract: It is necessary to incorporate the impact of climate change and economic growth on rainfall-runoff processes in advance. This study aimed to quantitatively analyze changes in runoff due to rainfall variations under climate change scenarios and land use variations under rural development scenarios. The study area was the Dau Tieng watershed in Southern Vietnam, with a total watershed area of 2700 km2. A distributed rainfall- runoff model was developed, which could overcome issues relating to calculation time and data scarcity in Southeast Asian watersheds. To capture a variety of land uses and spatially non-uniform rainfall characteristics of the tropical region, the distributed rainfall-runoff model was constructed by representing the watershed as a square mesh aggregate. To greatly reduce the calculation time, the original 90 m resolution digital elevation map data was scaled to a resolution of 4500 m. Four Sugawara’s tank models representing the rainfall-runoff characteristics of paddy, upland field, urban, and forest areas were incorporated into each mesh element to accurately represent land use in the watershed and simulate runoff from the different land uses. A watershed groundwater tank model covering the entire watershed was incorporated to represent a temporally stable base-flow component. Based on scenario analyses, future changes in rainfall-runoff processes with land use and rainfall changes were quantitatively evaluated not only using annual and peak runoff from the entire watershed but also changes in annual runoff and runoff patterns from each land use.
Year: 2020