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Water Supply of the Upper Colorado River Planning Area - Colorado River Water

Water supplies in the Upper Colorado River Planning Area include Colorado River water, other surface water, groundwater, and effluent. Colorado River water is the primary water supply in the Lake Havasu and Lake Mohave basins.  It is also used to meet environmental water demands for the Havasu National Wildlife Refuge in the Sacramento Valley Basin.  Elsewhere, groundwater is the primary water supply.  A discussion of Colorado River water entitlements and accounting is presented here.  Subsequent water supply and demand discussions and basin chapters report the use of Colorado River water as either groundwater, if it is pumped from a well within the hydraulically connected aquifer, or as surface water when it is directly diverted from the river.

Decree Accounting

The right or authorization to beneficially use Colorado River water is defined as an entitlement.  Entitlements held by Colorado River water users are created by decree of the United States Supreme court in Arizona v. California et al. (Decree), through a contract with the Secretary of the Interior (Secretary) under Section 5 of the Boulder Canyon Project Act (BCPA) of December 21, 1928, or by Secretarial Reservation.

Table 4.0-7 Arizona v. California Decree Accounting of the Consumptive Use of Colorado River Water in the Upper Colorado River Planning Area (in acre-feet per year)

Click to view Table 4.0-7

Table 4.0-7 shows the average annual Colorado River water that was consumptively used within each basin in the planning area based on an accounting system established by Decree.  Article V of the Decree directs the U.S. Bureau of Reclamation (Reclamation) to prepare an annual report of diversions from the mainstream, return flows to the mainstream that makes water available for downstream consumptive use in the U.S. or in satisfaction of the Mexican Treaty obligation, and the consumptive use of such water.  The Article V report lists diversions and return flows separately by diverter for each lower basin state.

According to the Article V report, consumptive use of Colorado River water in the planning area for agricultural, municipal, industrial and environmental purposes averaged 107,923 AFA for the 2001-2005 time period. Table 4.0-7 lists the total quantities of Colorado River water diverted by surface water diversions, in-river pumps, or pumped from wells assumed to be located within the hydraulically connected aquifer of the Colorado River.  When determining consumptive water use, the Article V accounting system considers measured return flow and estimates of unmeasured return flows to the mainstream.  

Reclamation has made a preliminary delineation of the lateral and vertical extent of the Colorado River aquifer to provide a basis for accounting of withdrawals against river water allocations.  On July 16, 2008, Reclamation proposed to develop a rule for Regulating Non-Contract Use of Colorado River Water in the Lower Basin (73 Federal Register 40916 et seq.) to prevent non-contract Colorado River water use from depleting the river and taking water from holders of Colorado River water entitlements.  Reclamation’s most current assessment indicates that most existing non-contract water use results from water withdrawn from wells located within the hydraulically connected aquifer of the Colorado River or from river pumps. The proposed rule would establish a methodology that Reclamation would use to determine if a well pumps Colorado River water and a process for a water user to appeal a subsequent finding (USBOR, 2008). As of June 2009, Reclamation had not adopted a rule.

Because of the complexity of the accounting system and its unique methodology that includes return flow and other considerations, the surface water and groundwater discussions in this overview section and the cultural water demand tables in sections 4.2, 4.3, 4.5, 4.6 and 4.9 (those basins that utilize this supply), reflect the amount of water pumped from wells and diverted from streams. This approach is comparable to that used for other planning areas. The tables do not attempt to distinguish whether the water is used pursuant to the Colorado River entitlement system. 

Havasu National Wildlife Refuge

Colorado River, Lake Mohave Basin

Entitlement Priority Levels

Rights to Colorado River water include the following priority levels in the State of Arizona: 

a. 1st Priority: Satisfaction of Present Perfected Rights as defined in the Arizona v. California decree;

b. 2nd Priority: Satisfaction of Secretarial Reservations and Perfected Rights established prior to September 30, 1968;

c. 3rd Priority: Satisfaction of entitlements pursuant to contracts between the United States and water users in Arizona executed on or before September 30, 1968 (2nd and 3rd priority are coequal);

d. 4th Priority: i) Contracts, Secretarial Reservations and other arrangements between the U.S. and water users in Arizona entered into after September 30, 1968, for a total quantity not to exceed 164,652 acre-feet of diversions annually and ii) contract No. 14-06-W-245, dated December 15, 1972, as amended, between the United States and the Central Arizona Project (CAP).  Entitlements having a 4th priority as described in (i) and (ii) are coequal;

e.   5th Priority: Unused Arizona entitlement; and

f.    6th Priority: Surplus water

Lake Havasu

London Bridge, Lake Havasu City

In general, the lower priority entitlements will be the first to be impacted when the Secretary declares a shortage on the Colorado River system.  Within the planning area, entitlement holders with a first priority or present perfected rights include the Fort Mojave Indian Reservation and several private entities within the Mohave Valley Irrigation and Drainage District.  Second and third entitlement holders (which are coequal during a shortage), include Havasu National Wildlife Refuge, Bureau of Reclamation (Davis Dam), and the National Park Service.  Fourth priority entities include Arizona-American Water Company (Lake Havasu), Bullhead City, Golden Shores Water Conservation District, Lake Havasu City, Mohave Water Conservation District, Mohave Valley Irrigation and Drainage District, and the Mohave County Water Authority.  Lake Havasu City and the Mohave County Water Authority also have fifth and sixth priority entitlements.

Mohave County Water Authority

The Mohave County Water Authority (MCWA) was organized pursuant to A.R.S.§ 45-2201 primarily for the purpose of acquiring the city of Kingman’s unused 18,500 acre-feet entitlement and making it available to other authority members for municipal and industrial water uses.  Authority members include Arizona-American Water Company, Bullhead City, Golden Shores Water Conservation District, Kingman, Lake Havasu City, Mohave County, Mohave Valley Irrigation and Drainage District and Mohave Water Conservation District.  As well as providing other services and functions, the Authority can acquire additional water supplies, including effluent, and it may store, recharge and recover these supplies for the benefit of Mohave County water users.  The Authority can also assist members with the development and operation of water diversion, conveyance, treatment, storage and recharge facilities and the development of augmentation and conservation programs.

Arizona Water Banking Authority

The Arizona Water Banking Authority (AWBA) was created in 1996 to protect Arizona’s Colorado River interests and to provide for interstate water banking opportunities.  Among its statutory authorities is the requirement to reserve a reasonable number of long-term storage credits developed with general fund appropriations for the benefit of Municipal and Industrial (M&I) water users located near the Colorado River (on-river users), during times of shortage.   Fourth priority on-river Colorado River M&I water users have no alternate water supply during times of shortage.  Regardless of whether water is diverted directly from the Colorado River or pumped from wells within the hydraulically connected river aquifer, the limit of an entity’s water right is its Colorado River entitlement.  On January 1, 1998, the AWBA adopted 420,000 acre-feet as the reasonable number of long-term storage credits for on-river M&I “firming.”  Contractors may recover this firmed or stored water in times of shortage. (For more information on the AWBA click here).

The manner in which the general fund credits would be reserved, and then recovered and distributed during a shortage, has long been an issue of concern to the on-river users.  In recognition of the concerns, the AWBA and the MCWA entered into the Agreement to Firm Future Supplies (Agreement to Firm).   The Agreement to Firm recognizes that the MCWA can enter into subcontracts with on-river M&I water users having the same priority as the CAP.  These are the same water users for whom the AWBA must firm M&I supplies.  Upon execution of the subcontracts and payment of the appropriate fees, the AWBA would reserve the appropriate quantity of long-term storage credits as described in the Agreement to Firm. 


The parties executed the Agreement to Firm on February 4, 2005.  The MCWA offered all entities in Mohave County the option to participate in the Agreement.  Subcontract entities included in the Agreement to Firm are Arizona State Parks, Bullhead City, Lake Havasu City, and Mohave Water Conservation District.  Pursuant to the Agreement to Firm, 230,280 acre-feet of the current 396,499 acre-feet of credits in the General Fund Account were transferred to a sub-account in MCWA’s name.  The remaining credits in the General Fund Account could still be available to firm on-river supplies.


The Colorado River reservoirs are operated in accordance with the Colorado River Basin Project Act of 1968 (P.L. 90-537).  Hydrologic conditions in the Colorado River Basin affect reservoir operation.  The Colorado River Basin experienced five consecutive years of extreme drought during water years 2000-2004 and, while there was above average inflow to Lake Powell and record-breaking tributary flows in the Lower Colorado Basin in 2005, there was below average streamflow in 2006 and 2007 (USBOR, 2006a and 2007c).  During this period, storage in Colorado River reservoirs dropped from near capacity to 54 percent of capacity by the end of 2007.  Conditions improved somewhat in 2008 but by April 2009 Lake Powell water levels were at 52% of capacity. 

Lake Mead Elevation

Figure 4.0-13 Lake Mead End of Month Elevation 1980-2006

Reclamation lacked specific guidelines to address the operation of Lake Mead and Lake Powell during drought.  To address this situation, in February 2007, Reclamation released a draft environmental impact statement on proposed adoption of specific interim guidelines for Lower Basin shortages and coordinated operation of the two reservoirs. The Final EIS was adopted in November 2007 and the Record of Decision was signed in December (USDOI, 2007). One of the purposes of the guidelines is to provide greater predictability regarding the amount of annual water deliveries to mainstream Colorado River water users in the Lower Division states (USBOR, 2007a).  The effect of drought and other hydrologic conditions on water levels in Lake Mead is shown in Figure 4.0-13.  Lowering water levels have resulted in closure and relocation of boat marinas at Lake Mead, and formation of a rapid at Pearce Ferry which had been a boat ramp.



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