Major aquifers, well yields, estimated water in storage, number of index wells and date of last water-level sweep are shown in Table 7.11-5.  Figure 7.11-7 shows aquifer flow direction and water-level change between 1990-1991 and 2003-2004.  Figure 7.11-8 contains hydrographs for selected wells shown on Figure 7.11-7.  Figure 7.11-9 shows well yields in five yield categories.  A description of aquifer data sources and methods as well as well data sources and methods, including water-level changes and well yields are found in Volume 1, Appendix A. 

Major Aquifers

• Refer to Table 7.11-5 and Figure 7.11-7.
• The major aquifer is basin fill.
• Flow direction is generally toward the Colorado River and south toward Mexico.

Well Yields

• Refer to Table 7.11-5 and Figure 7.11-9.
• As shown on Figure 7.11-9, well yields are generally greater than 2,000 gallons per minute (gpm). 
• One source of well yield information, based on 327 reported wells, indicates that the median well yield is 2,456 gpm.
• The line of wells along the international boundary is the 242 Well Field.  These wells collect groundwater and deliver it via the 242 Lateral to Mexico to meet a portion of the International treaty obligations.

Natural Recharge

• Refer to Table 7.11-5.
• The natural recharge estimate is 213,000 acre-feet per year (AFA).

Water in Storage

• Refer to Table 7.11-5.
• Storage estimates range from 34 million acre-feet (maf) to 49 maf to a depth of 1,200 feet. 

Water Level

• Refer to Figure 7.11-7. Water levels are shown for wells measured in 2003-2004.
• The Department annually measures 11 index wells in this basin. Hydrographs for 10 of these wells are shown on Figure 7.11-8. 
• The deepest water level shown on the map is 152 feet on the Mexican border and the shallowest is nine feet east of Yuma.

Table 7.11-5 Groundwater Data for the Yuma Basin

Figure 7.11-7 Yuma Basin Groundwater Conditions

Figure 7.11-8 Yuma Basin Hydrographs Showing Depth to Water in Selected Wells

Figure 7.11-9 Yuma Basin Well Yields

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References and Supplemental Reading for the Yuma Basin