AN ACTION PROGRAM FOR CONSERVING WATERS OF THE COLORADO RIVER, USA
Abstract
The Colorado is one of the world's great riverso One of the longest on the
North American Continent, it rises in the Rocky Mountains of the United States of America 14,000 feet above sea level, and flows 1,400 miles south-westwardly through deep canyons and across desert valleys, to empty into the Gulf of California on the Pacific Ocean.
The Colorado River has been manls lifeline in the southwest since he settled in the basin 2,000 years ago. The river continues to be a lifeline, but the demands of an exploding population have placed new strains on the stream's insufficient water supply.
The Federal Government established the Colorado River Indian Reservation in 1865 near Parker, Arizona. And 2 years later, a white man named Jack Swilling diverted water from the Salt River to grow food and forage near Phoenix,
Arizona. The Federal Reclamation development of the Colorado River Basin began in 1903, a year after passage of the National Reclamation Act, with authorization of the Salt River Project in central Arizona. The Yuma Project, authorized in 1904, became the first Reclamation project on the lower Colorado River.
Multipurpose Hoover Dam, completed in 1935, controlled the Colorado River for the first time. This pioneer or forerunner of the great Reclamation dams serves a multiplicity of purposes, including flood control, improvement of navigation and river regulation, water storage for irrigation, domestic and
industrial uses, hydroelectric power generation, recreation, fish and wild-life benefits, and sediment control.
Hoover Damqs control of the Colorado River made it possible to construct the All-American Canal System and other projects downstream.
Hoover Dam stood for many years as the only major storage structure on the river. Completion of Glen Canyon Dam, 370 miles upstream, in 1964 has afforded additional and similarly effective control.
Glen Canyon Dam is the backbone of the revenue-producing Colorado River Storage Project, authorized in 1956. Other storage units of this project are Flaming Gorge Dam on the Green River, Navajo Dam on the San Juan River, both completed, and three dams on the Gunnison River, two of which are under construction. The project's hydroelectric powerplants will have 1.3 million kilowatts of installed capacity. There are 28 participating irrigation proj-ects, now in all stages from early planning to completion, which will benefit nearly 1.5 million acres of land in the project area.
The inadequacy of the Colorado River to meet the water needs of the Colorado River Basin has highlighted the need to seek new sources of water, and to conserve that now available. Accordingly, the Department of the Interior has proposed the Pacific Southwest Water Plan, which calls for conservation and development of water resources on a regional basis. The plan recommends a 5-State regional complex of dams, hydroelectric plants, aqueducts, canals, water salvage, and conservation programs. Meanwhile, the Bureau of
Reclamation is active in water salvage and conservation programs such as channelization, phreatophyte eradication, evaporation control studies, groundwater recovery, and sea water desalinization studies. All of these programs are aimed at the conservation and utilization of e~ery available drop of water in the Colorado River Basin.
AN ACTION PROGRAM FOR CONSERVING WATERS OF THE COLORADO RIVER, USA Paper by Assistant Commissioner Gilbert C. Stamm, Bureau of Reclamation, United States Department of the Interior, for presentation at Sixth Regional Conference on Water Resources Development, sponsored by the Economic Commission for Asia and the Far East, Bangkok, Thailand, November 12-19, 1964
Historical
The Colorado River in North America--like the Mekong River in Southeast Asia--is one of the great rivers of the world. Both are lifelines--the Colorado River to the Pacific Southwestern United States of America and the Mekong River to the Asian States, This paper is about the Colorado River--the old and the new in its million-year history.
The Colorado River is one of the longest rivers on the North American Continent. It rises in the snowcapped mountains of the northcentral part of the State of Colorado at an altitude of 14,000 feet, and zigzags southwestwardly for 1,400 miles to pour into the Gulf of California. The Colorado River's basin covers 242,000 square miles in the United States, or one-twelfth of the country's continental land area, and 2,000 square miles in Mexico. Parts of seven large Western States drain into this mighty river system.
Through the ages, the river has slashed great gorges and chasms like world-famous Grand Canyon--a titanic cleft 217 miles long, from 4 to 18 miles wide, and a mile deep.
From lofty mountain tops and through deep canyons, the river makes its way across desert plains bordered by mountain ranges--the hottest, driest region in the United States, where temperatures run as high as 125 degrees Fahrenheit, and rainfall as low as an average of 3 inches a year.
Man's trek to the banks of the Colorado River and its tributaries began 2,000 years ago. The Ho-ho-kam Indians (meaning people who are gone) settled in the Salt River Valley of Arizona along the banks of the Salt and Gila Rivers, tributaries to the Colorado River. When the Spaniards arrived centuries later looking for gold and new territories to claim, they found dried-up canals and other remains of this ancient civilization. The Ho-ho-kam had left. Why? Perhaps their brush dams on the Salt and Gila Rivers could not control the floods and store water for their crops; or, it might have been because their lands became waterlogged. Historians just don't know.
The Spaniards found Indians living along the Colorado River and its tribu-taries. These Indians--who are believed to have migrated to the North American mainland from Asia many centuries ago--planted corn, squash, and
other seeds along the riverbanks, letting spring floods irrigate and
sprout them. Later on in the summer these early settlers dipped water from the streams to hand-irrigate their meager crops.
Man's dependence on the Colorado River has grown with migration from east to west, across the North American continent. Colorado River water has been a major determining factor in the rapid population and industrial growth of the Colorado River Basin States into which several thousand people are pouring daily. This growth has far outstripped the Colorado River Basin's water supply and that supply which one day seemed limitless is now being overdrawn. Today, more than 10 million people in the basin depend on water and power benefits from the Colorado River. The river annually irrigates more than a million acres of farmland, generates nearly
5 billion kilowatt-hours of hydroelectric energy, and provides vast bodies of water for recreation, fish and wildlife.
First Irrigation
Step by step over the last 100 years, man has put to use the Colorado River's water. The river's development, as we know it today, began in 1865 when the United States Congress established the Colorado River Indian Reservation on
the lower river to provide for settlement of several tribes. Meanwhile, a pioneer named Jack Swilling in 1867 dug a ditch from the Salt River through what is now the heart of Phoenix, Arizona, and irrigated a sizeable acreage of food and fiber. Some years later, in the early 1880's, Thomas H. Blythe established the white man's first irrigation development in the Palo Verde Valley of California on the Colorado River.
Near the turn of the century, private irrigators diverted Colorado River water to Imperial Valley in California through the old Alamo River bed which ran in part through Mexico. At this same time, settlers along the Colorado and Gila Rivers near Yuma, Arizona, were irrigating adjacent flood plain
lands from those streams and more remote areas from wells.
But farming was uncertain, and often disastrous. These streams were often rivers of mud when spring floods swept away farms and towns. Conversely,
they became rivers of dust when they dried to a trickle in the late summer and fall. Then, crops, livestock, and man thirsted, suffered and often died. Without upstream control, there was either too much or too little water.
Though underdeveloped and erratic, the muddy Colorado River was manls life-line in this arid area. He settled out the red mud and drank the water. He diverted the river--mud and all--onto his fields. He learned how the river got its name "Colorado," meaning "red."
Federal Development Began in 1902
It took a great catastrophe to spur man to push for control of the Colorado River. In 1905, the river broke through its banks below the Mexican border and for 2 years flowed unchecked into Imperial Valley of southern California--forming the Salton Sea which still exists as mute testimony to the river's vagaries. Similar tragedies--resulting in great losses of life and property--occurred elsewhere on the river and its tributaries. Settlers pleaded for help--for protection against the river. Many people in authority heard
them--understood their problems. Among these was President Theodore Roosevelt, 26th President of the United States. The settlers, however, lacked the money and knowledge to build the dams and canals needed to give them a year-round regulated water supply. Congress, therefore, in 1902 provided the means for furnishing both money and technical assistance by passing the Reclamation Act. The Act, amended since to encompass all of the multipurposes of water resources development, launched the Federal Reclamation program.
The Salt River Project in central Arizona on the Gila River, a tributary of the lower Colorado River, was authorized a year later and construction followed. The project's key storage structure, Theodore Roosevelt Dam, was dedicated in 1911 by the President for whom it was named. The Yuma Project near the Mexican border was authorized in 1904 as the first Reclamation development on the lower Colorado River. Reclamation's first dam on the
Colorado River, Laguna, which diverted water to the Yuma Project, was com-pleted in 1909.
Arthur Powell Davis, Reclamation Director and Chief Engineer, is considered to be the father of the present Federal Colorado River development which was highlighted by construction of Hoover Dam in the 1930's. Davis had traveled up and down the Colorado River surveying--looking over potential damsites. In 1918, Davis proposed to the Congress that the Federal Government build a dam of unprecedented height and size in a canyon on the Colorado River between Nevada and Arizona. A year later, a special board recommended construction of the All-American Canal, which would solve the many complexities of divert-ing water through the Alamo River channel in Mexico to Imperial Valley in southern California. In 1922, Secretary of the Interior Albert Fall and Reclamation Director Davis recommended to the Congress that both the high dam and the All-American Canal be constructed as one project.
Colorado River Compact
However, the seven Colorado River Basin States demanded that their respective rights to the stream's water be spelled out before any action was taken to authorize the project. This resulted in the signing of the Colorado River Compact by representatives of the seven Basin States at Santa Fe, New Mexico, November 24, 1922. The Colorado River Compact divided the Colorado River Basin into the Upper and Lower Basins at Lee Ferry, a point on the main stream about midway. The Upper Basin States include those parts of Arizona, Colorado, New Mexico, Utah and Wyoming within and from which water naturally drain into the Colorado River system above Lee Ferry in northern Arizona, The Lower Basin States include those parts of the States of Arizona,
California, Nevada, New Mexico and Utah within and from which waters naturally drain into the river's system below Lee Ferryo The Colorado River Compact apportioned water from the Colorado River system in per-petuity to the Upper Basin and to the Lower Basin, respectively.
Initial Legislation and Construction
The first legislation to authorize the high dam and canal Davis envisioned, which we know today as Hoover Dam and the All-American Canal System
compris-ing the Boulder Canyon Project, was introduced the year the Compact was signed and enacted in 1928. The Boulder Canyon Project Act approved the Colorado River Compact and authorized construction of the dam to provide flood control; improvement of navigation and regulation of the flow of the Colorado River; storage and delivery of stored waters of the Colorado River for reclamation of public lands and other beneficial uses exclusively within the United States; and the generation of electrical energy.
The Boulder Canyon Project Act also established liThe Colorado River Dam Fund" for financing construction. The Secretary of the Interior was required to provide for revenues adequate to insure operation, maintenance and
amortiza-tion of the construcamortiza-tion cost of the dam. These revenues were to repay, within 50 years, all advances for construction of the dam and its powerplant with interest, except for $25 million allocated to flood control.
Construc-tion of Hoover Dam was started in 1931 and was completed in 1935, 2 years ahead of schedule. Hoover Dam and Lake Mead, behind the dam, are the Western Hemisphere's highest dam and largest man-made lake. Imperial Dam and the All-American Canal were started in 1935 and completed in 1940.
Other Reclamation works on the lower Colorado River were being constructed during this period. Parker Dam, 155 miles downstream from Hoover Dam, was designed and constructed by the Bureau of Reclamation with funds advanced by the Metropolitan Water District of Southern California. Parker Dam
primarily provides a forebay and desilting basin for the District's Colorado River Aqueduct, which delivers water to the Los Angeles and San Diego metro-politan areas. The construction of Parker Dam began in 1934 and was
com-pleted in 1939. Davis Dam, 67 miles downstream from Hoover Dam, was completed in 1953 to provide regulation of Colorado River water delivered to Mexico at the International Boundary, as required by the Mexican Water Treaty. The Davis Powerplant teams with Hoover and Parker Powerplants to service markets in the Pacific Southwest. The three plants have a combined capacity of
1-2/3 million kilowatts. Davis Dam and Powerplant, Parker Dam and Powerplant, and a 1,600-mile transmission system serving Nevada, California, and Arizona, comprise the Parker-Davis Project.
Other construction included the Gila Project, comprising 115,000 acres of land in Arizona near the Mexican border. The Gila Project system delivered its first water to the Yuma Mesa Division in 1943, and to the Wellton-Mohawk Division in 1952.
The Bureau of Reclamation completed the Palo Verde Diversion Dam--its last barrier on the lower Colorado River--in 1957. The dam diverts water into the Palo Verde Irrigation District's canal system, now serving about 85,000 acres in California's Palo Verde Valley.
An International Stream
Like many rivers of the world, the Colorado is an international stream, serv-ing the United States and Mexico. It originates in the United States, and flows across the International Boundary, forming the line between the Mexican States of Baja and Sonora, and empties into the Pacific Ocean in the Gulf of California. A treaty between the United States of America and the United Mexican States relating to the division of the waters of the Colorado and Tijuana Rivers, and of the Rio Grande River, was signed by representatives of the two Governments in Washington, D. C. on February 3, 1944, and was ratified by the United States and Mexican Senates the following year. The treaty requires the United States of America to deliver a minimum of 1-1/2 million acre-feet of water each year across the border to Mexican water users, except in years of extraordinary drouth, when the delivery may be less. The offstream Senator Wash Dam and Regulating Reservoir, now under construction near Imperial Dam, will facilitate the scheduling and delivery of water to downstream users in the United States and Mexico and thus con-serve an average of 170,000 acre-feet of water annually,
Basking in year-round sunshine, the low-lying valleys in Arizona and California along the lower Colorado River were the first to tap and make use of the stream's flow. The so-called "easy" projects, to which water from the river could be diverted by gravity, were the first to be developed. Irrigable lands in the Upper Basin were not so fortunate. Most of the Upper Basin lands were considerably higher than the river and thus beyond
the reach of gravity flow. This explains in part why the lower Colorado River Basin projects were developed ahead of those in the Upper Basin.
Upper Colorado River Basin
But, at present, the upper Colorado River Basin States are developing their water resources on a large scale under the Colorado River Storage Project Act which the United States Congress authorized in 1956. This Act authorized the construction of four large storage units with a combined capacity of 34 million acre-feet, all of which are under construction or completed, Colorado River Storage Project hydroelectric powerplants, along with several small power-plants on the participating irrigation projects, will have a total installed capacity of about 1,300,000 kilowatts,
Of the dams, Flaming Gorge Dam on the Green River in northern Utah and Navajo Dam on the San Juan River in northern New Mexico are completed and work is underway on the Curecanti Unit on the Gunnison River in Colorado. Glen Canyon Dam on the Colorado River in northern Arizona, 370 miles upstream from Hoover Dam, is the keystone of the Colorado River Storage Project. The 710-foot-high concrete dam--only 16 feet lower than Hoover Dam--was topped out in 1963 and is substantially complete, Storage of water in the dam's reservoir--Lake Powell~
began in March 1963 and hydroelectric power generation in Glen Canyon Dam's 900,000-kilowatt powerplant began in the fall of 1964.
Colorado River Storage Project has 28 participating irrigation units, now in all stages from early planning to completion of construction. These projects will benefit a total of 1,448,000 acres of land, about 835,000 acres of which are now inadequately irrigated. The Colorado River Storage Project--like the Boulder Canyon Project and other basin developments--will also provide water for cities and factories, recreation, fish and wildlife, flood control and silt control benefits,
Transmountain Diversions
Transmountain diversion projects are very important in the Bureau of Reclama-tion's utilization of the Colorado River's flow. What is perhaps the Bureau of Reclamation's most spectacular transmountain diversion effort--the
Colorado-Big Thompson Project--was constructed a score of years ago. The l3-mile-long Alva B. Adams Tunnel takes Colorado River water through the Con-tinential Divide from the west side to the east side more than 5,000 feet below the crests of the Rocky Mountains. This project has served as a model in constructing other great transmountain diversion projects in other countries such as the Snowy Mountains Project in Australia. Many of the Australian
engineers who are building that project trained in our Chief Engineer's office in Denver, doing much of their design work there. The Bureau of Reclamation has started construction of another transmountain diversion system in
Colorado the Fryingpan-Arkansas Project. This recently authorized project will transport water from the Colorado River watershed eastward across the Continental Divide by tunnel to the Arkansas River. It is another step in the development of projects to utilize the Upper Colorado River Basin's share of water allocated under the Colorado River Compact.
Water Shortage
Up to the last 2 years there has been no major upper basin storage capacity. Flows far in excess of the annual 7.5 million acre-feet, which the upper basin must deliver to the lower basin under terms of the Colorado River Com-pact, have gone into storage in Lake Mead above Hoover Dam. Released through the Hoover Dam hydroelectric turbines, these waters generated electrical energy and made possible the tremendous agricultural, municipal. and
industrial growth in the lower basin, particularly in southern California. During recent years, however, the annual yield of the Colorado River water-shed has been substantially below earlier average flows. The increased usage in the upper basin, together with the current water drought, has created a water shortage crisis in the basin, particularly in the Pacific Southwest. Secretary of the Interior Stewart L. Udall, more than a year ago, warned that the Colorado River Basin was facing a water crisis and appointed a task force to investigate a 5-State Regional Plan which would develop new sources of water and conserve that which we now have. The objective was to design a plan which would utilize and conserve every available drop of water.
Pacific Southwest Water Plan
The Bureau of Reclamation's report on this plan--the Pacific Southwest Water Plan--has had initial hearings before the Congress. The plan calls for
immediate authorization for Federal construction of two dams between Hoover and Glen Canyon Dams, above and below the world famous Grand Canyon of the Colorado. Hydroelectric revenues from these two dams--Marble and Bridge Canyon--and from Hoover, Davis and Parker Dams when the construction costs of the latter are fully paid out, will go into the Pacific Southwest Develop-ment Fund to help pay for the wide range of projects needed to meet the region's water needs.
The Pacific Southwest Water Plan also may provide for enlargement of a por-tion of the California Aqueduct of the $2 billion California State Water Plan, now under construction by the State of California, to convey nn
additional 1.2 million acre-feet of water per year from the Sacramento-San Joaquin River Delta southward into southern California.
In addition to Marble and Bridge Canyon Dams, the plan calls for immediate authorization of the Central Arizona Project (with Hooker Dam and Reservoir in New Mexico as one of its components); the Southern Nevada Water Supply Project; the Moapa Valley Pumping Project, Nevada; and the Dixie Project, Utah. On September 2, 1964, the Congress authorized the Dixie Project.
The Pacific Southwest Water Plan proposes continued construction of irriga-tion distribuirriga-tion and drainage systems on the Colorado River Indian Reserva-tion and other Indian reservaReserva-tions in the lower basin. Also, new fish hatcheries, wildlife refuges and other fish and wildlife facilities are planned. Water salvage problems such as lining of the All-American and other canals, eradication of undesirable phreatophytes, channelization of streams, and evaporation control are an integral part of the plan.
Desalinization
More research and development in the reuse of waste water and desalinization of sea water are a part of the Pacific Southwest Water Plan. Great quantities of sewage and industrial water are flowing to the sea unused. This water can be reclaimed and reused to recharge underground aquifers and for industrial uses. Also, there is unlimited water that can be taken from the seas through
large desalinization plants. The Department of the Interior's Office of Saline Waters and private firms are doing extensive pilot plant testing of this process. Progress in this field promises to reduce the cost of desalted water so that it will become competitive with other sources for municipal and
industrial water and even for irrigation water in some cases. Coastal
cities may well obtain their supplies from such plants in the not too distant future, making surface water supplies available in greater quantity to inland cities.
It is possible that great nuclear electric generating plants will turn out large quantities of fresh distilled water as a joint function, The Office of Science and Technology, a part of President Johnson1s White House Staff, has published results of a study in this field which indicates that large, combination power-water desalinization plants could be developed using nuclear energy by about 1975-80 at costs which could be reasonably amortized. Stated more specifically, combined installations producing 1,000 to 1,500 megawatts of marketable electrical energy and 500 to 800 million gallons of water per day, with the water costing 20 to 25 cents per thousand gallons at the plant site (exclusive of conveyance costs) and the electric power valued at 2,3 to 2.5 mills per kilowatt-hour, can be envisioned by about 1975 if an appropriate research and development program is actively pursued.
And while we look to the Pacific Southwest Water Plan, its conservation pro-grams and its studies on reuse and desalinization, we go ahead with conserva-tion and salvage programs now underway.
Evaporation Retardation
Scientists estimate that up to 25 million acre-feet of water are being evaporated from exposed bodies of water in the Western States each year. Lake Mead is losing by evaporation a maximum of 7 feet off its top every year and other reservoirs and bodies of water in the hot southwestern desert are
losing similar amounts. This has caused the Bureau of Reclamation to join other agencies in research to stop this staggering annual loss. We have conducted tests on Lake Mead on the Colorado River and at Lake Sahuaro behind Stewart Mountain Dam on the Salt River. A large scale research proj-ect on Lake Sahuaro, using a monomolecular chemical film, a mixture of hexa-decanol and octohexa-decanol, has shown promise.
Channelization and River Control
The Colorado River Front Work and Levee System Act of June 28, 1946, gave the Bureau of Reclamation the authority to perform channelization, riverbank stabilization, and other river control work. The Bureau of Reclamation currently is channelizing a l6-mile stretch of the Colorado River through the Cibola Valley after completing 32 miles of new channel 125 miles upstream in the Mohave Valley below Davis Dam. These two dredging projects, in addi-tion to other planned channelizaaddi-tion work, will result in an overall saving of about 190,000 acre-feet of water which we estimate is being lost every year. Ground-water recovery would make available an annual average of 220,000 acre-feet of water for future beneficial use along the lower Colorado River. These waters would be pumped from the ground-water reservoir on the Yuma Project. Undesirable phreatophytes now infest over 160,000 acres of Federal and nonarable Indian land on the flood plain of the Colorado River. These water-robbing plants consume many thousands of acre-feet of water every year. Mechanical eradication of these worthless plants and future control with
chemicals combined with the construction of 141 miles of drains, would effect the salvage of an estimated 100,000 acre-feet of water annually on 42,000
work and levee system program, including the savings to be realized by the construction of Senator Wash Dam and Reservoir, it is conservatively esti-mated that a total of 680,000 acre-feet of water will be salvaged on the Colorado River annually.
Water Management
Several of the irrigation organizations are lining their canals, farm laterals, and making other water saving improvements under the Rehabilitation and Better-ment and Small Project Loans programs. For example, the Salt River Water Users Association has lined 129 miles of canals and laterals, and has replaced 211 miles of unlined laterals with concrete pipelines, since it began its rehabilitation program 14 years ago. Many of its open laterals have been placed underground in monolithic cast-in-p1ace concrete pipe. To date, $12.8 million has been spent on its rehabilitation and betterment program. This project has also made substantial progress in measuring water deliveries with resultant water savings. Several years ago it installed a pushbutton automatic gate control system on its main canals, which is considered to be one of the finest and most modern in the world.
The current water shortage on the Colorado River has prompted the Bureau of Reclamation to call upon water users to practice the utmost frugality in water use. More careful scheduling of water deliveries, more prudent
tion practices, more precise land leveling, and generally improved irriga-tion project operairriga-tions have become the rule throughout the Colorado River Basin.
Atmospheric Water Resources
A newly organized Office of Atmospheric Water Resources in the Bureau of Reclamation is presently commencing an expanded program in the field of weather modification. The major endeavor will be in the Colorado River-Continental Divide area where a long-range atmospheric water development program will attempt to produce and document precipitation increase by artificial cloud nucleation. Because of the extensive Bureau system of storage reservoirs, increases in precipitation, especially in the winter snowpack, will provide additional storage water for late season irrigation in this water-hungry Colorado River Basin. This program will be carried out by contracts and memorandum agreements with universities, private and Federal agencies.
Sediment Retention
Sediment retention is one of Hoover Dam's major benefits. Engineers set aside approximately 3 million acre-feet of the reservoir's original
32 million acre-feet capacity for accumulation of sediment. The Bureau of Reclamation has engaged the U. S. Coast and Geodetic Survey to conduct a hydrographic survey to determine the quantity of sediment deposited in Lake Mead since the first such study was completed 15 years ago. This sur-vey will be especially meaningful because it is timed to coincide approxi-mately with the closing of the gates at Glen Canyon Dam which thereafter will trap about 75 percent of the sediment in the Colorado River above Lake Mead. Meanwhile, below Imperial Dam and the All-American Canal Desi1ting Works, a dredge has constructed a sediment retention basin and inlet channel as part of the silt removal program.
Multipurpose Water Use
The Bureau of Reclamation operates its reservoirs on the Colorado River, for a multiplicity of purposes. These include flood control, irrigation, municipal and industrial use, hydroelectric power production, recreation, fish and wild-life and sediment control. These functions are not always compatible, in fact, they frequently are at least to some extent in competition one with another. Thus, at times, it is not possible to operate multiple-purpose projects in such a way as to provide maximum benefits to each of the several purposes. In this respect our objective and policies are to assign priorities of use to each purpose and adopt operating criteria which will maximize bene-fits to the various functions without infringing on the legal and contractual obligations of the project to its primary functions. Within this framework it frequently is possible to adopt year-to-year or day-to-day operational procedures which maximize the compatibility of conflicting functiDns.
Hoover Dam's primary purpose is to control and store the yearly floods which formerly caused destruction along the lower Colorado River. Lake Mead has been operated on a flood control schedule according to criteria developed
jointly by the U. S. Army Corps of Engineers and the Bureau of Reclamation. Operating regulations require that adequate reservoir space be available at certain specified seasons to accommodate anticipated inflow. For example, the reservoir is drawn down to its lowest point by mid-April and that point is determined by the amount of space required to hold the forecasted April through July runoff, which averages about 8.3 million acre-feet of water, well over half of the river's annual flow. Lake Mead will continue to have
upstream reservoirs of the Colorado River Storage Project will be considered in determining space required at any given time in Lake Mead. An expected result is that Lake Mead will be operated at higher water levels hereafter and will not fluctuate so greatly during the year.
The Bureau of Reclamation's River Control offices in Boulder City, Nevada, and Salt Lake City, Utah, keep close watch over the water supply and related conditions on the Colorado River. Reservoir storage and releases are sched-uled seasonally, monthly, and even daily, to meet the complicated and inter-related project functions recognizing requirements for flood control space, demands for irrigation water, demands for municipal and industrial water, opportunities and commitments for power generation, commitments and needs for fish and wildlife enhancement, and opportunities to enhance recreational benefits.
In summary, the Colorado River has been the life blood of the civilization in the Pacific Southwest as we know it today. Since Hoover Dam initially created the vast storage capacity in Lake Mead, a plentiful water supply has been available in all years to those who had rights and facilities for tak-ing it. But with the rapid population expansion in the Colorado River Basin and the current drouth cycle, the need for virtually complete control of the river for long-range carryover is clearly evident. Even then, the Lower Colorado River area will continue to be a water-deficient area and must look elsewhere than the Colorado River Basin for its future water requirements.
The Pacific Southwest Water Plan and other even more comprehensive projects of the future obviously are needed and will eventually be built to keep
water flowing in the farmer's furrow, and in the water pipes of homes and factories in the great Southwest. Thus the long-range development program for the Colorado River Basin envisions not only the complete development and control of the river resources but integration of water resources from
several major basins into a unified water plan which may well involve the United States, Canada, and Mexico.
