水だめ is read as みずだめ (mizudame) and means sump.
みずだめ
mizudame
みずがめ
water jug
すいしゃ
violent wielding of weapons
みず
break granted to wrestlers engaged in a prolonged bout
すいちゅう
underwater
みずけ
water vapor (vapour)
みずいらず
(being) by oneself
すいじょう
aquatic
みずたまり
puddle
みずき
dogwood (Cornus controversa)
すいせい
aquatic (life)
みずいり
みずかさ
volume of water (in a river, pond, flood, etc.)