https://www.mlit.go.jp/mizukokudo/watersupply/content/001741376.pdf
https://www5.cao.go.jp/keizai-shimon/kaigi/special/reform/ab1/20220411/shiryou19-5.pdf
https://www.kubota.co.jp/corporatehistory/ourchallenges/japan-water-02/3/
https://www.soumu.go.jp/main_content/000968725.pdf
https://www.mlit.go.jp/mizukokudo/watersupply/content/001741376.pdf