Hydrogeology of Cibola County, New Mexico

The hydrogeology of Cibola County, New Mexico, was evaluated to
determine the occurrence, availability, and quality of ground-water
resources. Rocks of Precambrian through Quaternary age are present in
Cibola County. Most rocks are sedimentary in origin except for
Precambrian igneous and metamorphic rocks exposed in the Zuni Uplift
and Tertiary and Quaternary basalts in northern and central parts of the
county. The most productive aquifers in the county include (youngest
to oldest) Quaternary deposits, sandstones in the Mesaverde Group, the
Dakota-Zuni-Bluff aquifer, the Westwater Canyon aquifer, the Todilto-
Entrada aquifer, sandstone beds in the Chinle Formation, and the San
Andres-Glorieta aquifer.

Unconsolidated sand, silt, and gravel form a mantle ranging from
a few inches to 150 to 200 feet over much of the bedrock in Cibola County.
Well yields range from 5 to 1,110 gallons per minute. Dissolved-solids
concentrations of ground water range from 200 to more than 5,200
milligrams per liter. Calcium, magnesium, bicarbonate, and sulfate are
the predominant ions in ground water in alluvial material.

The Mesaverde Group mainly occurs in three areas of the county.
Well yields range from less than 1 to 12 gallons per minute. The
predominant ions in water from wells in the Mesaverde Group are calcium,
sodium, and bicarbonate. The transition from calcium-predominant to
sodium-predominant water in the southwestern part of the county likely
is a result of ion exchange.

Wells completed in the Dakota-Zuni-Bluff aquifer yield from 1 to 30
gallons per minute. Dissolved-solids concentrations range from 220 to
2,000 milligrams per liter in water from 34 wells in the western part of
the county. Predominant ions in the ground water include calcium, sodium,
sulfate, and bicarbonate. Calcium predominates in areas where the aquifer
is exposed at the surface or is overlain with alluvium.

Sandstones in the Chinle Formation yield from 10 to 300 gallons per
minute to wells in the Grants-Bluewater area. In the western part of
the county, sodium and bicarbonate predominate in water from the Chinle
Formation. In the eastern part of the county, water quality is more
variable than elsewhere and the predominant constituents include
calcium, sodium, sulfate, and chloride.

Well yields from the San Andres-Glorieta aquifer in the Grants-
Bluewater area are as much as 2,830 gallons per minute, whereas the
maximum recorded pumping rate from the aquifer in other areas of the
county is 88 gallons per minute. Dissolved-solids concentrations of
ground-water range from about 130 to 4,200 milligrams per liter, and the
water generally is a calcium bicarbonate sulfate type.