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Water Supply of the Southeastern Arizona Planning Area - Groundwater

Water supply in the Southeastern Arizona Planning Area inlcudes Surface Water, Groundwater and Effluent.  Local aquifers are the primary water supply for the planning area for municipal, industrial and agricultural use as shown in Figure 3.0-13.  Approximately 15% of the cultural water demand is served by surface water.  Most of the surface water is for agricultural use, and includes diversion from the San Pedro River, Aravaipa Creek and the Gila River. Gila River diversions are substantial, accounting for 92% of all surface water diversions in the planning area during the period 2001-2005. Small amounts of surface water are diverted for municipal use in the Morenci, Upper San Pedro and Willcox Basins and for industrial use in the Morenci Basin.  Some communities utilize effluent for golf course irrigation and for groundwater recharge.  Sites of environmental contamination may impact the availability of water supplies in some locations.


Groundwater is the major water supply in the planning area, meeting 85% of the total demand, 92% of the municipal demand, 83% of the agricultural demand and 97% of the industrial demand during the period 2001-2005. The location of registered exempt and non-exempt wells is shown in Figure 3.0-14. Groundwater is the sole supply utilized in Bonita Creek, Cienega Creek, Donnelly Wash, Douglas, Dripping Springs Wash, San Bernardino Valley and San Rafael Valley basins. Major aquifers supplying groundwater are basin fill, sedimentary rock (Gila Conglomerate), volcanic rock and recent stream alluvium. Groundwater is relatively abundant and well yields are high in most basins.

Water supply

Figure 3.0-13 Water Supply Used in the Southeastern Arizona Planning Area

In the north and northeastern portion of the planning area (Bonita Creek, Dripping Springs Wash, Duncan Valley and Morenci basins), groundwater development is primarily from wells that tap the younger basin fill or the Gila Formation.  Median well yields from large (>10 inch diameter) wells ranges from 395 gpm in Dripping Springs Wash Basin to over 1,100 gpm in the southern part of Bonita Creek Basin. Estimated groundwater in storage ranges from as low as 150,000 acre-feet in Dripping Springs Wash Basin to as high as 19 maf in the Duncan Basin.

Groundwater is a stock and domestic supply in the Bonita Creek and Dripping Springs Wash basins. In the Duncan Valley Basin groundwater meets about half (10,000 acre-feet) of the agricultural demand and supplies all the municipal and industrial water.  Groundwater is the primary water supply for mining and municipal uses in the Morenci Basin.


Cotton in Safford

Cotton in the Safford Basin. 

The Safford Basin contains almost 5,000 registered wells that utilize basin fill, the major aquifer, and the stream bed alluvium along the Gila River drainage.  Well yields are generally high with a median well yield of 600 gpm reported from almost 1,500 wells. Groundwater in storage may be as high as 69 maf in the basin. While surface water is an important agricultural water supply in the basin, groundwater is now the largest supply utilized, with over 121,000 acre-feet pumped annually from the basin during the period 2001-2005, particularly from the Gila Valley sub-basin, which contain the basin’s population and agricultural centers.

Basins located on the western side of the planning area (Aravaipa Canyon, Donnelly Wash, Cienega Creek, Lower and Upper San Pedro), yield groundwater from the stream alluvium and basin fill. Most irrigation wells are located in the stream alluvium while most industrial and domestic wells are located in the basin fill. Stream alluvium aquifers support stock, agricultural and domestic uses in the northern and southwestern parts of the Cienega Creek Basin, while basin fill is the principal aquifer in the central valley.

As shown in the groundwater data tables for each basin, median well yields range from 62 gpm in the Donnelly Wash Basin to as high as 1,000 gpm in the Lower San Pedro Basin. Groundwater in storage estimates range from as low as 140,000 acre-feet in the relatively undeveloped Donnelly Wash Basin to as high as 26.1 maf in the populous Upper San Pedro Basin.

Groundwater supplies the domestic and about half of the small scale farming demands in the Aravaipa Canyon Basin. Historically, mining and grazing activities were also important land and water uses.  Groundwater is the sole water supply available for domestic uses in the Donnelly Wash Basin and for municipal, agricultural and industrial purposes in the Cienega Creek Basin. All of the industrial demand, the largest demand sector in the Lower San Pedro Basin (almost 16,000 AFA), is met by groundwater, which is also the primary water supply for agricultural and municipal purposes.  In the Upper San Pedro Basin, groundwater meets almost all the municipal demand (17,300 AFA) and the majority of the agricultural demand.

Almost all the water supply available for agricultural, municipal and industrial purposes in the Willcox Basin is groundwater found primarily in basin fill deposits. Median well yield is 750 gpm with as much as 59 maf of groundwater in storage (Table 3.14-6). Groundwater has been heavily utilized for agricultural purposes for many years and there are concerns about the future availability of this water supply, prompting recent water level monitoring investigations (USGS, 2006b). 

The three basins with groundwater outflow to Mexico have differing groundwater supply conditions. In the San Bernardino Valley Basin, groundwater is obtained from thin units of sand and gravel interbedded with basalt flows or from shallow alluvium. There are only 12 registered wells with a pump capacity greater than 35 gpm in the basin with a range of 22 to 600 gpm reported for three of them.  Groundwater is the water supply for stock and domestic uses. The main aquifer in the Douglas Basin is basin fill, which is used to support extensive agricultural irrigation in the basin. As with the Willcox Basin, there are concerns about the long-term pumpage of groundwater from the basin aquifers and future groundwater supply availability. Protection of the groundwater supply from agricultural expansion was first initiated in 1965 when the area was designated as a Critical Groundwater area and its subsequent designation as an Irrigation Non-expansion Area in 1980. In the City of Douglas area, groundwater is pumped from basin fill with interbedded volcanic rock. Median well yield in the Douglas basin is 600 gpm (Table 3.5-6).  In the San Rafael Basin, where ranching is the primary activity, groundwater is obtained from stream alluvium and basin fill and median well yields are about 145 gpm from large diameter wells (Table 3.12-6).


Windmill in the San Rafael Basin

San Rafael Basin


The Department’s Groundwater Site Inventory (GWSI) database, the main repository for statewide groundwater well data, is available on the Department’s website.  The GWSI database consists of over 42,000 records of wells and over 210,000 ground-water level records statewide. GWSI contains spatial and geographical data, owner information, well construction and well log data, and historic groundwater data including water level, water quality, well lift and pumpage records. Included are hydrographs for statewide Index Wells and Automated Groundwater Monitoring Sites, which can be searched and downloaded to access local information for planning, drought mitigation and other purposes. 

Approximately 1,700 wells are designated as Index Wells statewide out of over 43,700 GWSI sites. (GWSI sites are primarily well sites but include other types of sites such as springs and drains). Typically, index wells are visited once each year by the Department’s field staff to obtain a long-term record of ground water level fluctuations. Approximately 200 of the GWSI sites are designated as Automated Wells. These systems measure water levels 4 times daily and store the data electronically. Automated groundwater monitoring sites are established to better understand the water supply situation in areas of the state where data are lacking.  These devices are located based on areas of growth, subsidence, type of land use, proximity to river/stream channels, proximity to water contamination sites or areas affected by drought.

Volume 1 of the Atlas shows the location of index wells and automatic water-level recording sites as of January, 2009.  At that time there were a total of 250 index wells and 9 ADWR automatic water-level sites in the Southeastern Arizona Planning Area.  The automated sites are located at Bowie, Sunizona, Kansas Settlement, near Sierra Vista, south of Safford, Benson (3) and near the San Pedro River near the southern boundary of the Lower San Pedro Basin. The most updated maps may be viewed at the Department’s website.

Information on major aquifers, well yields, estimated natural recharge, estimated water in storage, aquifer flow direction, and water level changes are found in groundwater data tables, groundwater conditions maps, hydrographs and well yield maps for each basin in the basin sections.


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