13:45 〜 14:00
[AHW18-11] Predicting the impact of climate change on stream temperatures according to watershed geology
★Invited Papers
キーワード：気候変動、河川水温、流域地質
Climate change is expected to have an impact on stream ecosystems due to rising water temperatures, including a reduction in suitable habitats for cold-water species in snowy regions. One of the factors controlling stream water temperature is the extent of groundwater inflow according to the basin geology; however, there was no method available to estimate stream water temperature using the amount of groundwater inflow in a process-based model. In the current study, we predicted future changes in stream water temperature using a water temperature estimation model based on the basin water cycle and reflecting differences in the watershed geology.
A model was developed to estimate stream flow and temperature according to two geological features, Quaternary volcanic rocks and Mesozoic rocks, for a watershed ranging from a few km2 to several hundred km2 in the upper reaches of the Sorachi River in Hokkaido, Japan. The model comprised a combination of models representing atmospheric and land surface processes, slope runoff, and stream network runoff processes. For slope runoff, different parameters were set for different geologic characteristics, and these parameters were used to calculate the response of water temperature to changes in past climate (end of the 20th century) and future climate (end of the 21st century in the IPCC RCP 8.5 scenario).
The model was verified to reproduce observed stream flow and water temperature with reasonable accuracy. The contribution of basal runoff is large in the Quaternary volcanic rock areas, suggesting that this stabilizes the stream flow and temperature throughout the year. The model was then used to predict future stream flow and water temperature under future climatic conditions. In the Quaternary volcanic rock distribution area, which is rich in groundwater runoff, summer water temperatures were kept lower than those in the Mesozoic distribution area, and the mean daily water temperature exceeded 20°C less frequently, indicating that these areas provide a refuge from the climate change for cold-water species vulnerable to high water temperatures. Further investigation will make it possible to utilize the data for the conservation and restoration of habitats of cold-water species.
This study was funded by a fund for the Ishikari and Tokachi Rivers (FY2018-FY2022) provided by the Ministry of Land, Infrastructure, Transport, and Tourism of Japan.
A model was developed to estimate stream flow and temperature according to two geological features, Quaternary volcanic rocks and Mesozoic rocks, for a watershed ranging from a few km2 to several hundred km2 in the upper reaches of the Sorachi River in Hokkaido, Japan. The model comprised a combination of models representing atmospheric and land surface processes, slope runoff, and stream network runoff processes. For slope runoff, different parameters were set for different geologic characteristics, and these parameters were used to calculate the response of water temperature to changes in past climate (end of the 20th century) and future climate (end of the 21st century in the IPCC RCP 8.5 scenario).
The model was verified to reproduce observed stream flow and water temperature with reasonable accuracy. The contribution of basal runoff is large in the Quaternary volcanic rock areas, suggesting that this stabilizes the stream flow and temperature throughout the year. The model was then used to predict future stream flow and water temperature under future climatic conditions. In the Quaternary volcanic rock distribution area, which is rich in groundwater runoff, summer water temperatures were kept lower than those in the Mesozoic distribution area, and the mean daily water temperature exceeded 20°C less frequently, indicating that these areas provide a refuge from the climate change for cold-water species vulnerable to high water temperatures. Further investigation will make it possible to utilize the data for the conservation and restoration of habitats of cold-water species.
This study was funded by a fund for the Ishikari and Tokachi Rivers (FY2018-FY2022) provided by the Ministry of Land, Infrastructure, Transport, and Tourism of Japan.