Lake Intake?

Lake Cachuma (or Cachuma Lake, if you prefer) is reporting at increasing levels of water containment, and always 193,000-plus acre-feet is shown as “capacity.” Is that true? How is capacity measured? And if that measurement is based on the original size and capacity of the lake when the dam was closed, has silting over the years since then been taken into account? Might the true capacity now be significantly less?