Montezuma Well

Montezuma Well (Yavapai: ʼHakthkyayva or Ahagaskiaywa), a detached unit of Montezuma Castle National Monument, is a natural limestone sinkhole near the town of Rimrock, Arizona through which some 1,500,000 US gallons (5,700,000 L; 1,200,000 imp gal) of water emerge each day from an underground spring. It is located about 11 miles (18 km) northeast of Montezuma Castle.

The Well measures 386 feet (118 m) in diameter from rim to rim and contains a near-constant volume of spring water even in times of severe drought. The water is highly carbonated and contains high levels of arsenic. At least five endemic species are found exclusively in Montezuma Well: a diatom, the Montezuma Well springsnail, a water scorpion, the Hyalella montezuma amphipod, and the Motobdella montezuma leech — the most endemic species in any spring in the southwestern United States.

Montezuma Well's steady outflow has been used for irrigation since the 8th century. Part of a prehistoric canal is preserved near the park's picnic ground, and portions of the canal's original route are still in use today.

As with Montezuma Castle, the label "Montezuma" is a misnomer: the Aztec emperor Montezuma had no connection to the site or the early indigenous peoples that occupied the area.

Montezuma Well is geologically very similar to the sinkholes and cenotes found in Florida and the Yucatán peninsula of Mexico - that is, a limestone cave that has collapsed to expose its subterranean water source. The Well sits at the northern end of what is called the Verde Limestone formation, a distinct layer of travertine limestone - more than 2,000 feet (610 m) thick in some places - deposited beneath a series of shallow lakes that covered Arizona's central Verde Valley region between eight and two million years ago.

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