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Miguel and Dolores Rivers begin near the southwestern corner of the state and flow north along the <br />western border. The San Juan River and its tributaries collect the water in the southernmost regions of <br />Colorado west of the Continental Divide and carry it through northwest New Mexico and southeastern <br />Utah to Lake Powell. <br />The Colorado River flows through Utah to Lake Powell, thence through the northwest corner of Arizona to <br />Lake Mead. From Hoover Dam it flows southward to Mexico forming the border between Nevada, <br />California and Arizona, and yielding major diversions to central Arizona and southern California. The river <br />is the lifeblood of the southwestern US and its development and management have been the focus of <br />attention by the member states for more than a century. Waters of the Colorado River System have been <br />apportioned by a treaty with Mexico, compacts, and a Supreme Court decree to the seven basin states. <br />WATER MANAGEMENT ISSUES <br />Compacts, an international treaty, a Supreme Court decree and numerous Federal and State laws play <br />an important role in Colorado River water management. The Colorado River Compact of 1922 divided the <br />use of waters of the Colorado River System between the Upper and Lower Colorado River Basin. It <br />apportioned in perpetuity to the Upper and Lower Basin, respectively, the beneficial consumptive use of <br />7.5 million acre feet (maf) of water per annum. It also provided that the Upper Basin will not cause the <br />flow of the river at Lee Ferry to be depleted below an aggregate of 75 maf for any period of ten <br />consecutive years. The Mexican Treaty of 1944 allotted to Mexico a guaranteed annual quantity of 1.5 <br />maf. These amounts, when combined, exceed the river's long-term average annual flow. <br />~1~r~.~~ Fir pp~rti~rLmnt <br />~f <br />Lower <br />Basin <br />(7.5 maf <br />Within Colorado water allocations are based on the Doctrine of Prior Appropriation or the First-in-Time, <br />First-in-Right Doctrine. This doctrine is found in most arid states because when there is too little water to <br />satisfy all users, sharing of the remaining water would be of little value to any user. Also, some guarantee <br />of water is required to secure the value of investments. These appropriative rights are administered by <br />Division of Water Resources (DWR) officials who follow state law and established procedures in <br />administering and allocating water to users according to decreed priorities. <br />It is of great interest to the State and other water users to be able to assess the impacts of water rights <br />transfers or water resource developments. Water rights in Colorado can be viewed as private property <br />whereby a individual owns the rights to beneficial use of the water. These rights can be changed from one <br />type of use to another or from one place to another, but only if no other water right is injured. Such <br />changes require water court approval. Because changes of agricultural ditch and reservoir rights to <br />municipal use are fairly common, concerns arise over whether a transfer of water will affect the supply <br />available to owners of other decreed water rights. <br />Upper Mexico <br />Basin (1.5 maf) <br />