Aztec Ruins Water Investigation

Christensen, Paul

Aztec Ruins National Monument is situated in northwestern New Mexico near the town of Aztec by the Animas River. The ruins at the monument have been a subject of concern in order to preserve them from avoidable water deter!oration. A subsurface drainline was emplaced across the northern end of the monument to lower the water table beneath the ruins. Six observation wells were drilled to observe the fluctuation and depth to static water level. No records were kept of the above activities. A riparian woodland has encroached upon the northeast corner of the monument. The monument lies on the alluvial fill of the Animas River. Pleistocene sand and gravel terraces are located about 1200 feet north of the monument. The valley sides are of the Paleocene Nacimiento formation, which is predominantly a shale. The Nacimiento also underlies the alluvium and terraces. The alluvium produces large quantities of fair quality water to wells. The Nacimiento is a poor aquifer. The Aztec Ruins well log and samples from the three observation wells drilled July 1979 reveal that the monument is underlain by a clay unit 10 to 30 or more feet thick, and suggest that the drainline constructed lies in this clay aquitard. The drainline does not affect the groundwater in the sand and gravel aquifer beneath the clay aquitard. However, the drainline does remove some water from the aquitard. Irrigation water on fields north of the monument drains into a pond on the north side of the monument. At times, this water flows through breaks in. the dikes which contain the pond into the vegetal encroachment. This flooding is responsible for the encroachment.