water storage capacity; volume of stored water
Refers to the amount of water held in a reservoir, tank, or similar facility. Often used in technical or news contexts.
The dam's water storage level is below the average year.
The storage capacity of this water tank is 500 liters.
水量 is a general term for water volume, whereas 貯水量 is specifically about stored water.
Compound of 貯水 (water storage) and 量 (amount, quantity).