A unit of volume used by engineers to describe a large quantity of water. One milliard equals one cubic kilometer, which is 1 billion (109) cubic meters or about 810 767 acre feet
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}