Long-term change of river water temperature flowing into reservoirs in Japan

Yusuke Kume, Makoto Umeda

Research output: Contribution to conferencePaperpeer-review

Abstract

Reservoirs play an important role in flood control and water use. In particular, from the viewpoint of water use, they are responsible for the major resources of domestic water in Japan as well as agriculture and industrial waters. On the other hand, various impacts from climate change are becoming apparent in various areas in recent years. Eutrophication phenomenon, especially occurrence of water bloom by cyanobacteria, seems more frequent possibly because of changes in river water discharge and nutrient load affected by alteration of precipitation as well as rising water temperature. Water temperature is generally considered the principal factor to control water quality and ecosystem in natural water bodies. In this study, we investigated the long-term changes in water temperature observed over the past several decades in many dam inflow rivers in all parts of Japan. The observed date of water temperature and air temperature contain seasonal periodic components, which were removed using Fourier series approximation to extract long-term trend components. The relationship between the long-term trend of water temperature change, meteorological data such as air temperature and precipitation, and geographical data with respect to the watershed of the reservoir were then analyzed. The air temperature tended to rise at the most of the reservoirs. On the other hand, a number of inflowing rivers exhibited decreasing trends in water temperature. Besides, the changes of the water temperature and the air temperature were almost uncorrelated. In addition, although some correlation was observed between other meteorological data and geographic data, and water temperature, it was not sufficient to express the change tendency of water temperature.

Original languageEnglish
Publication statusPublished - 2020
Event22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Creating Resilience to Water-Related Challenges, IAHR-APD 2020 - Sapporo, Virtual, Japan
Duration: 2020 Sep 142020 Sep 17

Conference

Conference22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Creating Resilience to Water-Related Challenges, IAHR-APD 2020
Country/TerritoryJapan
CitySapporo, Virtual
Period20/9/1420/9/17

Keywords

  • Climate change
  • Regression analysis
  • River water temperature

ASJC Scopus subject areas

  • Ecology
  • Environmental Engineering

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