Highland Basins

The Highland Basins include the Salt River, Tonto Creek and Verde River basins, and the northern half of the Agua Fria Basin.  Basin-fill aquifers in the highlands are limited in areal extent and are hydrologically connected with stream alluvium.  Consolidated rock aquifers surround and underlie the basin-fill aquifers and contribute underflow. Basin-fill aquifers also receive inflow from stream infiltration and mountain front recharge.  Where the basin-fill aquifers are discontinuous, underflow between them may be restricted (Anderson, et al., 1992).

Tonto Creek Basin

In the Tonto Creek Basin groundwater is found in stream alluvium, basin-fill sand and gravel, Paleozoic sedimentary rocks and Precambrian igneous, metamorphic and sedimentary rocks.  The primary aquifer occurs in basin fill, which underlies a large portion of the basin, from near Rye to the southern basin boundary.  The basin fill consists of coarse-grained conglomerate in the lower part of the basin and along the basin margins and locally is overlain by fine-grained mudstone in the center of the basin.  The conglomerate may be up to 500 feet thick.  Groundwater is also found in the floodplain alluvium, which may be as much as 65 feet thick along Tonto Creek.  Along this Creek, the basin fill and alluvial aquifers are recharged primarily by stream infiltration.

A limestone aquifer is utilized along the Mogollon Rim where groundwater movement and well yield are dependent on faults, fractures and solution cavities.  Wells in the limestone aquifer generally yield less than 100 gpm.  Fractured bedrock also yields small volumes of water to wells east of Payson (ADWR, 1992).   These and other sedimentary-rock aquifers are recharged from precipitation on the southern edge of the Colorado Plateau (USGS, 2005a). 

Groundwater flow directions are from the Mogollon Rim to the south in the C-aquifer and from north to south along the Rye Creek and Tonto Creek drainages in the alluvial aquifer (Figure 5.3-7).  Natural recharge for the basin has been estimated at 17,000 to 37,000 AFA.  Estimates of groundwater in storage range from 2.0 to 9.4 maf.  With one exception, all wells measured in 2003-‘04 had a water level below 100 feet. Water levels in wells measured between 1990-‘91 and 2003-‘04 were either slightly declining or slightly rising ((Figure 5.3-7).  The median well yield reported on registration forms for large (>10-inch) diameter wells was 120 gpm. Since most of the basin is National Forest land, there has been little basin-wide groundwater development and aquifer characteristics are not well defined.  Groundwater quality is generally good, although drinking water standards for arsenic, radionuclides, nitrate and organics have been equaled or exceeded in some wells.

Click for Figure 5.3-7 Tonto Creek Basin

Groundwater Conditions

Click for Figure 5.3-8 Tonto Creek Basin Hydrographs Showing Depth to Water in Selected Wells

Click for Figure 5.3-9 Tonto Creek Basin Well Yields

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References and Supplemental Reading for the Tonto Creek Basin