『保健医療科学』 2020 第69巻 第5号 p.425-433（2020年12月）
特集：気候変動による日常生活や健康への影響を考える＜総説＞
気候変動影響に対する水道システムの適応策
小坂浩司，秋葉道宏
国立保健医療科学院生活環境研究部
抄録
水道システムは，気候変動によって水質，水量，水道施設に対して様々な影響を受ける可能性がある．水質への影響として，藻類の増殖による異臭味等の生物障害，消毒副生成物前駆物質濃度の上昇による消毒副生成物濃度の上昇，洪水による濁度の上昇，塩水遡上による原水への塩分の混入等が挙げられた．近年は，大雨や台風にともなう洪水によって，水道施設が大きな被害を受け，大規模な断水につながっている．水道システムは，インフラ・ライフラインであるため，断水によって，国民生活や事業活動も甚大な被害を受ける．減断水被害は，渇水によっても毎年のように発生している．これらの影響に対して，様々な適応策が検討されている．全般的な対策として，水道システムの危害の特定とそのリスク評価，脆弱性評価（洪水リスクマップ，渇水リスクマップ等）がある．水質の場合，適応策の具体的内容は水質項目によって異なるが，水源での管理や浄水場での対応が挙げられた．水害や渇水については，応急給水体制等のソフト面の対応と，施設の設置や更新等のハード面の対応が挙げられた．これら適応策は，実際に取り組みが行われているが，今後は，気候変動影響を考慮した水道事業に関する計画や水安全計画の作成も重要であると考えられた．また，気候変動影響の評価を行う上で，対象項目の観測の継続や強化，将来予測データの活用が望まれる．
キーワード：気候変動，水道システム，水質，水害，渇水
Abstract
Water supply systems are affected in various ways by climate change, in terms of water quality, quantity, and facilities. The effects on water quality include taste and odor problems due to algae growth, increased concentrations of disinfection byproducts due to increased concentrations of their precursors, high turbidity due to flooding, and salt contamination in raw water due to salt water run-ups. In recent years, heavy rainfall and typhoon-related flooding have caused extensive damage to water supply facilities, leading to largescale water outages. As the water supply systems represent infrastructure lifelines, water cut-offs result in serious damage to the lives and business activities of people. In addition, droughts have also caused water cutoffs every year. A variety of adaptations were applied to meet these effects. General adaptations include the identification of hazards to the water supply systems, risk assessment, and vulnerability assessment (e.g., flood risk maps and drought risk maps). In the case of water quality, although the adaptations that are applied depend upon the specific water quality issues, watershed management at the water source, as well as treatment at the water purification plant were mentioned. For floods and droughts, both intangible adaptations such as the emergency water supply systems and tangible adaptations, such as the installation and renewal of facilities were applied. While these adaptations have been implemented in practice, it is also important to develop a water supply management plan and a water safety plan that properly take the impacts of climate change into account. In order to assess these impacts, it is necessary to continuously monitor target items and work to achieve their enhancement, while utilizing predictive data on climate change.
keywords: climate change, water supply system, water quality, flood, drought
