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Lower Colorado River Water Supply - Surface Water

Water supplies in the Lower Colorado River Planning Area include groundwater, surface water, Central Arizona Project (CAP) water and effluent.  As shown on Figure 7.0-13, most water used is surface water.  Colorado River water is the major supply in the Lower Gila, Parker and Yuma basins and CAP water is the largest supply in the Harquahala Basin. Gila River water combined with effluent discharge from the Phoenix AMA is an agricultural supply in the Gila Bend Basin.  Elsewhere, groundwater is the primary water supply.  Colorado River water is also used to meet environmental needs at the Imperial Wildlife Refuge in the Parker and Lower Gila basins. A discussion of Colorado River water entitlements and accounting is presented below.  For purposes of the Atlas, water diverted from a watercourse or spring is considered surface water and if it is pumped from wells it is accounted for as groundwater.  This is reflected in the cultural water demand tables in each basin section.

Figure 7.0-13 Average Annual Water Supply Utilized in the Lower Colorado River Planning Area, 2001-2005 (in acre-feet)

Figure 7.0-13

Surface Water

The Gila River in the Gila Bend Basin is the only major surface water supply in the planning area in addition to the Colorado River. The river is intermittent or ephemeral in the planning area and the volume available for use is a mixture of upstream releases of water from dams, storm runoff from precipitation events, irrigation return flows and effluent flows from the 23rd Avenue and 91st Avenue Wastewater Treatment Plants (WWTPs) located in the Phoenix AMA.  The 91st Avenue WWTP, located near the confluence of the Salt, Gila and Agua Fria Rivers, has a current treatment capacity of 179 mgd (over 200,000 AFA).  In typical years, most if not all water in this reach of the river is wastewater effluent (ADWR, 1994a).  An average of 54,000 AFA of this water supply is used for irrigation in the basin.

Gila River and Gilespie Dam

Gila River and Gilespie Dam, Gila Bend Basin.


Legal availability of a surface water supply is also an important consideration. The following discussion applies to non-Colorado River surface water. As described in detail in Appendix E, the legal framework and process under which surface water right applications and claims are administered and determined is complex.  Rights to surface water are subject to the doctrine of prior appropriation which is based on the tenet “first in time, first in right”. This means that the person who first put the water to a beneficial use acquires a right that is superior to all other surface water rights with a later priority date. Under the Public Water Code, beneficial use is the basis, measure and limit to the use of water. Each type of surface water right filing is assigned a unique number as explained in Appendix E and shown in Table 7.0-8. On the other hand, the act of filing a statement of claim of rights to use public waters (36) does not in itself create a water right. A Certificate of Water Right (CWR) may be issued if the terms of the permit to appropriate water (3R, 4A, or 33, and in certain cases 38), are met.  CWRs retain the original permit application number.

Surface water rights may also be determined through judicial action in state or federal court in which the court process establishes or confirms the validity of the rights and claims and ranks them according to priority. Court decreed rights are considered the most certain surface water right. A court decree, Arizona v. California 373 U.S. 546 (1963), confirmed the apportionment of waters from the mainstem of the Colorado River to the Lower Basin States, set Arizona’s allotment of Colorado River water at 2.8 maf and reserved irrigation water for reservations along the river including the CRIT, Cocopah and Quechan (Fort Yuma) reservations in the planning area.

Arizona has two general stream adjudications in progress to determine the nature, extent and priority of water rights across the entire river systems of the Gila River and the Little Colorado River. The adjudications will recognize existing water right settlements and decrees (see discussion below) and adjudicate all remaining water rights claims in the river systems. Pertinent to the Lower Colorado River Planning Area, the Gila River Adjudication is being conducted in the Superior Court of Arizona in Maricopa County. The Gila Adjudication was initiated by petitions filed by several parties in the 1970’s, including Salt River Project, Phelps Dodge Corporation and the Buckeye Irrigation Company. The petitions were consolidated in 1981 into a single proceeding. The Gila Adjudication includes seven adjudication watersheds - Upper Salt, San Pedro, Agua Fria, Upper Gila, Lower Gila, Verde, and Upper Santa Cruz.  Only the Lower Gila Adjudication Watershed is within the planning area boundaries (see Figure 7.0-15). This watershed includes all of the Gila Bend, McMullen Valley and Tiger Wash basins, most of the Lower Gila and Harquahala basins and a small part of the Yuma Basin. These watersheds do not coincide with the 6-digit HUC watersheds discussed previously and shown in Figure 7.0-5. The entire Gila Adjudication includes over 24,000 parties.

Table 7.0-8 Arizona v. California decree accounting of the consumptive use of Colorado River water in the

Lower Colorado River Planning Area (in acre-feet/year)

Table 7.0-8

Click to view Figure 7.0-14

Click to view Figure 7.0-15

Table 7.0-8 summarizes the number of surface water right filings in the planning area. The methodology used to query the Department’s surface water right and statement of claimant (SOC) registries is described in Appendix E.  Of the 3,142 filings that specify surface water diversion points in the planning area, 108 CWRs have been issued to date. Most of these (46) are located in the McMullen Valley Basin.  Figure 7.0-15 shows the general location of surface water diversion points listed in the Department’s surface water rights registry. The numerous points reflect the large number of stockponds and reservoirs that have been constructed in the planning area as well as diversions from streams and springs. Locations of registered wells, many of which are referenced as the basis of claim in SOCs are also shown in Figure 7.0-15.

The location of surface water resources are shown on surface water condition maps and maps showing perennial and intermittent streams and major springs for each basin, and in basin tables that contain data on streamflow, flood ALERT equipment, reservoirs, stockponds and springs.



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