To be fair it's really just an application of the same strange units. Once you've committed to acres for land and feet+inches for rainfall, acrefeet is the only

To be fair it's really just an application of the same strange units. Once you've committed to acres for land and feet+inches for rainfall, acrefeet is the only option you've really got for volume of rainfall. We have to fix land (square kilometers) and rainfall (millimeters) before we can fix volume of rainfall (cubic meters).