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Surface Water Conditions in the Lower Gila Basin

Streamflow data, including average seasonal flow, average annual flow and other information are shown in Table 7.4-2.  Flood ALERT equipment in the basin is shown in Table 7.4-3.  Reservoir and stockpond data, including maximum storage or maximum surface area, are shown in Table 7.4-4. The location of streamflow gages identified by USGS number, flood ALERT equipment, USGS runoff contours and large reservoirs are shown on Figure 7.4-4.  Descriptions of stream, reservoir and stockpond data sources and methods are found in Volume 1, Appendix A. 

Streamflow Data

  • Refer to Table 7.4-2.
  • Data from four stations located at three watercourses are shown in the table and on Figure 7.4-4.  Two stations have been discontinued and two are real-time stations.
  • Average seasonal flow varies at the four stations.  At one station, Colorado River below Imperial Dam, the average seasonal flow is similar in all seasons due to releases from Imperial Dam.  The Rio Comez station near Ajo, with a small, local drainage area, receives 79% of its average seasonal flow in the summer season (July-September).  The Gila River stations report highest average seasonal flow the spring (April-June) season.
  • The largest annual flow recorded in the basin is 10 million acre-feet in 1984 at the Colorado River below Imperial Dam station with a contributing drainage area of 188,500 square miles. 

Flood ALERT Equipment

  • Refer to Table 7.4-3.
  • As of October 2005 there were nine stations in this basin.

Reservoirs and Stockponds

  • Refer to Table 7.4-4.
  • The basin contains five large reservoirs.  The largest, Imperial, has a maximum surface area of 1,402 acres. 
  • Surface water is stored or could be stored in six small reservoirs in the basin. 
  • There are 65 registered stockponds in this basin.

Runoff Contour

  • Refer to Figure 7.4-4.
  • Average annual runoff is highest, 0.2 inches per year or 10.66 acre-feet per square mile, in the southeastern portion of the basin and decreases to 0.1 inches, or five acre-feet per square mile, in the remainder of the basin.

Click here for Table 7.4-2

Table 7.4-2 Streamflow Data for the Lower Gila Basin

Click here for Table 7.4-3

Table 7.4-3 Flood ALERT Equipment in the Lower Gila Basin

Click here for Table 7.4-4

Table 7.4-4 Reservoirs and Stockponds in the Lower Gila Basin

Click here for Figure 7.4-4

Figure 7.4-4 Lower Gila Basin Surface Water Conditions





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References and Supplemental Reading for the Lower Gila Basin

Colorado River
Lower Colorado River Planning Area
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Imperial Dam
Welton Mohawk Agriculture