According to Wikipedia, 11B cubic meters is the correct total capacity, with 8B cubic meters being the active capacity. Meaning, they try to keep it at 8B m^3,

According to Wikipedia, 11B cubic meters is the correct total capacity, with 8B cubic meters being the active capacity. Meaning, they try to keep it at 8B m^3, with 3B m^3 of flood-control capacity.