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The Lower Basin The Lower Basin states - with their rapidly growing cities such as Phoenix, Las Vegas. San Diego and Los Angeles - have driven the development of water for a century, beginning with California's efforts in the late 1800s to divert Colorado River water into the Palo Verde and Imperial valleys and in the 1920s in to the greater Los Angeles area. The ellort to increase Colorado River diversions continued through the years, and was joined by Arizona. and ultimately Nevada, both of which have seen dramatic population increases into the 21st century. Because the Lower Basin states could not reach agreement on apportionment of the Lower Colorado River under the Boulder Canyon Project Act. the secretary of the Interior - as watermaster through the Bureau - controls the lower Colorado River, in- cluding Lake Mead. A portion (~rrhe Central Arizona ProjecllranSpofts Colorado River 1Hlter through Scotf.wlale. Ar;zono. The Southwest experienced one of the most severe droughts on record from 1987.1992. The drought oc- curred at the same point in time the Lower Basin began using close to its full apportionment of 7.5 million acre- feet in years of "normal" water sup- ply. Under the Coordinated Long Range Operating Criteria of 1970, the secretary of the Interior is required to annually deter- mine whether a normal, shortage or surplus water supply condition exists. which governs whether the Lower Basin will receive 7.5 million acre-feet of water (normal) or more (surplus) or less (shortage) each calendar year. These factors motivated the seven basin states and 10 Tribes possessing water entitlements to the Colorado River to form a working group in 1991 to discuss and seek resolution to Colorado River issues of mutual concern. Included in the discussion were California's continued, long-term use of more than 4.4 million acre-feet per year when the Lower Basin unused apportionment ot Arizona and Nevada (that 16 California is using) would no longer be available due to the completion of CAP. Securing an additional water supply for the rapidly growing Las Vegas-area of Nevada also was given priority in the discussions. Other topics have included water demands. environmental needs, interstate water banking, river system operations and the leasing of water rights long held by American Indians. Historically. the leasing of Indian water rights has not been allowed. In 1994. the Bureau released a preliminary draN of regulations to add flexibility to the Law of the River and establish legal means to deal with unauthorized Colorado River water uses. The regulations generated a great deal of confroversy - delaying the Bureau's proposal. but extending the time for all the states and American Indian tribes to discuss water banking, interstate transfers and for California to develop a plan to reduce its annual Colorado River use to 4.4 million acre-feet when conditions on the river so dictate. In November 1999, an interstate bankmg rule - an oils hoot of the 1994 document - was released (see page 20). Issues such as water transfers and water banking are rapidly becoming the new water vocabu- lary for the Lower Basin as the three states adapt to a new era of water management. It has been strongly suggested by former Secretary Babbitl that California reduce its consumption by 800.000 acre-feet (to remain within the state's 4.4 million acre.feet allocation) and the state is developing a plan to do so. Nevada will soon outgrow its apportionment of the river and Arizona could hold the key to the future with the advent of its Arizona Water Banking Authority. Similarly, in 2000, Arizona and Nevada, in concert with the Upper Basin States and Interior. agreed to Interim Surplus Guidelines that will allow California to use additional water as it reduces its overall use of the river over the next 15 years (see page 21). Ironically. the Lower Colorado River (though highly impacted and modified) presently supports the most significant stocks of endangered fish. For the entire Colorado River Basin. the Lower Basin holds 97 percent of the adult population of razorback suckers - the only wild stock of bonytail chubs - and the largest stock of humpback chubs. The designation of nearly 1,800 miles of the Lower Colorado River as critical habitat has been a driving force behind establishing the Lower Colorado Multi- Species Conservation Program to recover endangered species, including the aforementioned native fish popufations.