US lawWashingtonRegulationsTitle 173 — ECOLOGY, DEPARTMENT OFChapter 173-500 — WATER RESOURCES MANAGEMENT PROGRAM ESTABLISHED PURSUANT TO THE WATER RESOURCES ACT OF 1971173-500-990WAC 173-500-990WAC 173-500-990. Map—Water resources inventory areas sub-basinsLast amended: 1976Year: 2026Length: 6 wordsOfficial source water resources inventory areas sub-basins .PreviousWAC 173-500-080