An acre-inch is defined as the volume of Environment-database.eu/cms/glossary/56-glossary-w/3441-water.html" title='Water is a liquid at normal temperatures but exists also solid (ice), and water vapor (cloud) in the air; A water molecule has the formula H2O which means that two hydrogen (H) atoms and. . .' rev="av:20190614002023">water that would be needed to cover an area of one acre to the depth of one inch. It is equal to 3630 ft³, 102.8 m3 or approximately 27154 (US, liquid) gallons.
The environment database and a glossary about facts, terms and descriptions