|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
The acre-foot is a unit of volume commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water, and river flows.
A traditional unit of volume for stone and other masonry. A perch of masonry is the volume of a stone wall one perch (16 1⁄2 feet or 5.03 metres) long, 18 inches (45.7 cm) high, and 12 inches (30.5 cm) thick. This is equivalent to exactly 24 3⁄4 cubic feet (0.92 cubic yards; 0.70 cubic metres; 700 litres).