Convert from gallon [US, liquid] to hectare meter

Unit Definition (gallon [US, liquid])
The gallon [US, liquid] is a traditional unit of liquid volume, derived from the Roman galeta, which originally meant a pailful. Gallons of various sizes have been used in Europe ever since Roman times. In the United States, the liquid gallon is legally defined as exactly 231 cubic inches; this is equal to the old English wine gallon, which originated in medieval times but was not standardized until 1707, during the reign of Queen Anne. Some scholars believe the wine gallon was originally designed to hold 8 troy pounds of wine. The U. S. gallon holds 4 liquid quarts or exactly 3.785 411 784 liters; a U.S. gallon of water weighs about 8.33 pounds. American colonists were also familiar with the Elizabethan beer and ale gallon, which held 282 cubic inches (4.621 liters).

Unit Definition (hectare meter)
The hectare meter is a unit of volume used to measure the capacity of reservoirs, equal to the volume of water one meter deep covering one hectare. The unit is used mostly in British Commonwealth countries, especially India, where it provides a metric unit comparable to the traditional English acre foot. Reservoir capacities are often stated in millions of hectare meters (Mha·m or MHM). One hectare meter equals exactly 10 000 cubic meters or about 8.1071 acre feet.