Research Objectives

  The objective of this research is to further improve the accuracy of assessments of climate change and adaptation measures by developing bottom-up and top-down models in the water resources sector, then making comparisons and assessments of these models and integrating them. For this purpose, a total of four subgroups―two dealing with water resources and two with water usage―are being established to realize improved accuracy of the bottom-up model, as well as one subgroup dedicated to the development of a top-down model.

① Research on water cycle assessment
  By gaining an understanding of hydrological and climatological changes throughout Japan using satellite data and field data, items directly connected to water usage and water-related disasters, such as the spatiotemporal distribution of rainfall at different catchment basin scales as well as changes in hydrology, water quality, and sediment production that constitute flood and drought hazards, will be quantitatively elucidated, including in terms of accuracy, targeting different areas in Japan.
  The existing water cycle/water environment/sediment analysis models targeted at the regional scale will be expanded and integrated into a nationwide model (upgraded version of bottom-up models).
  A stochastic impact projection method will be developed for flow regimes, interannual variations in water quality of inland waters, and sediment production at the national level based on multiple climate projection results using the latest high-accuracy and high-resolution climate models and impact assessment/projection models. The reliability of the method, degrees of vulnerability, etc. will be analyzed, information will be provided to the damage estimation team, and a plan for sustainable water policies and adaptation measures in Japan will be formulated.

② Assessment of impacts on water quality in water resources
  Data concerning quality of water resources (dam reservoirs) will be gathered and systematized. Moreover, a field survey of individual dam reservoirs will be implemented.
  A numerical analysis model for impact assessments of water quality in dam reservoirs will be constructed. Based on future climate scenarios, changes in water quality due to changes in hydrological conditions, etc. will be investigated and impacts on the quality of water resources nationwide will be assessed.

③ Assessment of impacts on small-scale water supply systems
  Data on rivers, groundwater, etc. that serve as sources of water for small-scale water supply facilities will be gathered to analyze the relationship between temperature increase and water quality changes in recent years. In order to gain an understanding of the actual conditions of water supply facilities with receiving tanks, data from the Ministry of Health, Labour and Welfare as well as from individual prefectures, etc. will be obtained and analyzed, and hearings will be held with water supply utilities, etc. Moreover, information on water supply on islands will be gathered.
  Field surveys targeting small-scale water supply facilities will be conducted to extract information on which aspects are susceptible to impacts of climate change, etc. in the processes of obtaining water resources, water purification, water distribution, etc., and the appropriateness of responses to climate change and possible response measures, as well as their costs, will be investigated. With regard to water supply facilities with receiving tanks, their actual conditions, especially in terms of which aspects are susceptible to impacts of climate change, will be investigated. Damage caused by climate change (warming) to small-scale water supply facilities and water supply facilities with receiving tanks will be compiled at the national level and the accuracy of projections will be enhanced. In addition, damage will be projected based on multiple stabilization scenarios utilizing information from the summarization team. The accuracy of projections will be enhanced through comparisons with the results of projections by a top-down model, and comprehensive projections related to water resources will be carried out.

④ Research on assessment of impacts on water supply in large urban areas
  Long-term trends in water usage in large urban areas will be elucidated, and the relationships between temperature on the one hand, and water demand, raw water quality, and the quantities of chemicals and energy used on the other, will also be clarified. In addition, the relationships between weather conditions other than temperature on the one hand, and water demand and the quantities of chemicals and energy used on the other, will be verified. A model that makes it possible to assess changes in urban water demand and changes in quantities of chemicals and energy used in water supply businesses under various scenarios will be developed. Assessments will be made targeting cities nationwide to elucidate the effects of locality, size factor, etc.
  Information on core facilities and main pipelines in large-scale water supply utilities will be gathered and systematized to investigate methods for easy development of water supply facilities in areas where they have not yet been developed. Scenarios of impacts on water supply systems based on climate change scenarios will be presented. A method for extracting which districts are vulnerable to flood risk from the projection of flood damage will be formulated. In addition, a model for projecting damage to water supply facilities in large urban areas will be developed. Damage to water supply-related facilities will be projected from the flood damage projections to estimate the number of days of water supply suspension, costs of restoration, etc. Damage projections will be made based on scenarios presented by the summarization team, aiming at consistency with the top-down model. The water supply facilities damage projection model, by which assessments can be made that incorporate damage reduction measures such as the existence of alternative water resources and connecting pipes, will be expanded. The reliability and scope of application of the developed model will also be clarified. A method for comprehensively assessing impacts of climate change on water supplies in large urban areas will be established in order to propose decision procedures for reducing damage, as well as adaptation measures based on the results. Comparison and consistency with impact assessments by the top-down model will be aimed at, and comprehensive impact assessments will be made in cooperation with the other teams.

⑤ Development of top-down model for impact assessment
  In cooperation with the summarization team, various types of information concerning population, land use, climate, water resources, and water usage in local government areas will be gathered to construct a database, and local government areas will be classified according to type. Important factors when assessing impacts on water usage by classified type of local area will be elucidated, an impact assessment method using these factors will be constructed, and quantitative variations in damage due to climate change as well as effective adaptation measures for each classified type of area will be investigated. Multiple climate change projection scenarios and adaptation measure scenarios provided by the summarization team will be analyzed, and nationwide damage as well as damage avoided due to adaptation will be projected in quantitative terms. The top-down model will also be improved and refined through comparisons with the results obtained for other subthemes.

Group members (*: Leader)

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