Montezuma Well, a Unit of Montezuma Castle National Monument, Rimrock, Arizona
Montezuma Well, 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) 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, amounting to approximately 15,000,000 US gallons (57,000,000 L). The water is highly carbonated and contains high levels of arsenic. At least five endemic species are found exclusively in Montezuma Well: a diatom, a springtail, a water scorpion, an amphipod, and a leech — the most endemic species in any spring in the southwestern United States. It is also home to the Montezuma Well springsnail.
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 Yucatan 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.
Archaeological evidence suggests that humans have lived in the Verde Valley for at least 10,000 years. The earliest signs of permanent settlement in the area appear quite a bit later, however, around 600 CE.
The ruins of several prehistoric dwellings are scattered in and around the rim of the Well. Their erstwhile inhabitants belonged to several indigenous American cultures that are believed to have occupied the Verde Valley between 700 and 1425 CE, the foremost of which being a cultural group archaeologists have termed the Southern Sinagua.
The earliest of the ruins located on the property (with the exception of the irrigation canal), a "pithouse" in the traditional Hohokam style, dates to about 1050 CE. More than 50 countable "rooms" are found inside the park boundaries; it is likely that some were used for purposes other than living space, including food storage and religious ceremonies.
The existence of the Well was almost unknown to European Americans before the publishing of Handbook to America by Richard J. Hinton in 1878. In 1968, Montezuma Well was the subject of the first ever underwater archaeological survey to take place in a federally managed park, led by archaeologist George R Fischer.
The Yavapai people consider the Well a deeply sacred site, as they believe it is the place through which they emerged into the world.
The high concentration of dissolved carbon dioxide gas in the water of the Well (which amounts to more than 80 times the typical freshwater concentration), and to a lesser extent its alkalinity, has prevented the development of any kind of fish population, so the Well remains a fishless spring. However, other types of aquatic life have managed to adapt: the Well supports at least five endemic freshwater species. Many different bird species feed on these organisms and the plant life found in the water.