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Little Colorado River Watershed Coordinating Council

The Little Colorado River occupies much of the northeast portion of Arizona.  There are two distinct volcanic fields in the basin: one in the west around Flagstaff and another in the southeast in the White Mountains area.  The Little Colorado River is the main drainage for the basin.  The river flows to the northwest from the White Mountains area, leaving the basin near Cameron, Arizona.  The Little Colorado River Plateau basin is bordered on the north by Arizona-Utah state line, on the east by the Arizona-New Mexico state line, on the south by the Mogollon Rim, and on the west by U.S. Highway 89.  The presence of U.S. Highway 89 does not have any hydrogeologic significance to the basin boundary, but happens to coincide with the lithologic and tectonic changes in the aquifer system.


 

Watershed Studies

 

Related Documents will be included here in future updates.

 

[ Back to Watershed Map ]

Elevations in the Little Colorado River Plateau basin vary from, to 4,200 feet above mean sea level where the Little Colorado River flows out of the basin.

Local Aquifers

Local aquifers are of great importance for domestic water supplies where the three regional aquifers, the D-, N-, and C-aquifers, are too deep or have unsuitable water quality.  The local aquifers include alluvial deposits, which occur in washes and stream channels throughout the basin, sedimentary and volcanic rocks, and various sandstones.

The alluvium along the Little Colorado River and its tributaries is an important local source of water for domestic supplies.  Water enters the alluvium as discharge from the D, N, and C-aquifers, as streamflow infiltration, or as direct rainfall.  In thicker sections the alluvium is a steady source of water, but smaller washes can go dry because of overuse or drought conditions.  Water quality varies greatly in the alluvial aquifers.

Basaltic volcanic rocks occur along the southeastern and southwestern edges of the Little Colorado River Plateau basin.  The basaltic rocks form an irregular, eroded surface and vary in thickness from 0 to 3,000 feet.  Groundwater is found in fractures, cinder beds, and heavily weathered zones.  In the southeastern part of Navajo County, the saturated basaltic rocks, together with underlying sedimentary rocks, locally are known as the Lakeside-Pinetop aquifer.  Water quality is generally very good and water is used for domestic, stock, irrigation, and Lakeside/Pinetop public supply purposes.

The Bidahochi Formation forms a local aquifer in the northeastern part of southern Apache County and near St. Johns.  The Bidahochi Formation is composed of sedimentary and volcanic rocks.  The formation generally has three members: a basal sandstone, a middle volcanic unit, and an upper sandstone member.  Principal groundwater withdrawal is from the upper sandstone unit.  Recharge is derived from rainfall onto the outcrop exposures.

Aquifers of the Little Colorado River Plateau basin contain large quantities of groundwater in storage; however, they are in a sensitive relationship with the Little Colorado River and its perennial tributaries.  Lowering of hydrostatic heads by excessive groundwater withdrawals may cause some perennial reaches of the streams to dry up (Mann, 1976).

The C-aquifer is the source of water for Sterling Spring at the head of Oak Creek in the Verde River basin.  Future development of this aquifer and the limestone aquifer in the Flagstaff area should be preceded by an area-wide hydrologic study.  Local heavy withdrawals from the C-aquifer may also cause upward shifting of the salt water interface from the evaporates in the Supai Formation near Joseph City (Mann and Nemecek, 1983).

The D- and C- regional aquifers are still in hydrostatic equilibrium (steady-state); however, local groundwater sinks or cones of depression are developing in areas of heavy pumpage (Arizona Department of Water Resources, 1991) such as the paper mill near Snowflake and three of the power plants: Springerville Generating Station, Coronado Generating Station (St. Johns), and Cholla Generating Station (Joseph City/Holbrook).  The Navajo Generating Station, near Page, uses surface water from Lake Powell.  Water levels in wells that tap the confined area of the N- aquifer are declining because of heavy withdrawals for the Black Mesa coal mine slurry pipeline.

 

 





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