Author(s): Yuki Inoue; Kei Nukazawa
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Keywords: Climate change; Environmental flow; Indicators of hydrologic alteration; Watershed management
Abstract: Climate change alters flow regime of river around the world these days, that leads to not only the occurrences of natural disasters such as flash floods and riverbank erosion, but also affects negative impacts on ecosystem like decreasing the area for some habitats. To date few studies have tackled evaluation of flow alterations involved with changing climates at a watershed scale. Here we evaluated retrospective climate-flow changes in multiple catchments in Japan and Indonesia, as well as their spatial patterns using a distributed hydrological model (DHM) and indicators of hydrologic alteration (IHA), which are popularly used environmental flow metrics that can assess variety of flow alterations including those related to ecosystem. DHM is a physically based distribution model that simulates hydrological processes of hillslope layers and channel stream flow throughout the watershed. We divided the study period into base and impact periods and the extents of the alterations were quantified by the ratio of IHA between those periods. One of the results shows that the monthly median flow during winter season increased although the flow during spring season decreased in the catchments in a catchment in southwest Japan. This is attributed to the decline of snowfall in winter due to temperature rise in the impact period compared with the base periods. In the same catchment, we also found significant positive alteration in the annual maximum daily streamflow over middle to upstream. This may cause negative impacts on the ecosystem especially in the upper streams through promoting hydraulic erosion and passive drifts of benthic animals.
Year: 2024