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LTHOUGH the present agricultural and commercial development of the Colorado River has been accomplished during the past 75 years, practically four centuries have elapsed since the first white man gazed upon its waters. During these centuries, the information left by the diaries of the intrepid Padres and explorers from time to time have given brief mention of the high waters and terrific floods which prevented their crossings or fought them in their endeavors to sail up the Lower River below Yuma.

The Colorado River has a total length of approximately 1750 miles, a drainage area of 244,000 square miles and a total annual water supply of approximately 21,700,000 acre feet. The larger portion of this water is supplied by the melting snow from the summit of the Rocky Mountains in western Colorado and Wyoming, but an appreciable portion is also furnished by the drainage area below the junction of the Green with the Colorado, a section subjected at certain seasons to violent storms of short duration commonly known as cloud-bursts. The effect of these storms and of the fluctuation in the melting snows is indicated by the differences in the river flow, annual discharges as great as 26,000,000 acre feet and as low as 8,000,000 acre feet having been recorded at Yuma.

Magnitude of Floods

While records have indicated the low flow of the river at less than 1300 cubic

feet per second or second feet, in flood season-May and June-the discharge at times is more than 200,000 second feet by actual measurement, and the flood of 1884 was estimated at 384,000 second feet. Marks left by high water at some time previous to known records would indicate a discharge greatly in excess of this figure and reaching possibly 500,000 second feet.

Silt

In addition, due to the flood characteristics and to the effect of heavy storms on a large portion of the area, as well as the soil and topography of the country through which it flows, the river carries a tremendous burden of silt estimated from direct measurements at approximately 113,000 acre feet, or more than 182,000,000 cubic yards per

annum.

Imperial Valley

Originally the Gulf of California extended approximately 200 miles north of its present shores and 100 miles north of the present Mexican boundaries into southeastern California. The Colorado River, heavily laden with the silt brought from the upper regions, has, during the centuries, deposited its burden as it entered the Gulf from the east side, gradually forming a huge delta which, working its way across, finally separated entirely the upper portion from the Gulf proper. After the separation and due to the silt formation, the river swung to and fro, flowing first into the Gulf and

then into the inland lake. The long intervals of time between, however, permitted the removal of the water by evaporation until finally a basin-like valley, now known as the Imperial Valley, some 40 miles in width and 80 miles in length, with its lowest point approximately 250 feet below sea level, is the result.

Though, due to the very meagre annual rainfall, this valley was one of the worst sections of desert traversed by the early pioneers, an ample water supply will make possible the irrigation of approximately a million acres of land unexcelled in richness within the United States.

Some 25 years ago a group of men with keen vision and faith in their convictions sensed the possibilities of this land, and after tremendous effort were successful in constructing the necessary works to bring water from the Colorado River to irrigate a part of the Imperial Valley. Today the results of such foresight and enterprise are shown by 462,000 acres of land reclaimed and under cultivation, a population of over 60,000 people with several well-built cities and an assessed property valuation of over $100,000,000.

Other Reclamation Projects

On the Arizona side, directly east of the Imperial Valley, is an equally fertile section of approximately 110,000 acres known as the Yuma Valley, and in addition, at various locations on both sides of the Lower River, are several projects including the Parker Project, 110,000 acres; the Palo Verde Valley, 78,600 acres; the Mohave Valley, 34,000 acres and the Cibola Valley with 16,000 acres; all of which, immediately adjacent to the river banks, have been formed by the deposition of silt. This land is extremely fertile and in a climate productive to the best form of agricultural development.

Flood Menace and Damage

The achievement in reclaiming the Imperial Valley has not been lightly won. The Colorado River, flowing along the eastern rim of the valley, has deposited a large portion of its silt along its bed, raising the level nearly a foot per annum until the river now flows on top of a silt ridge 300 feet above the lowest point of the valley.

Protective works of the levee type have been constructed at great expense to prevent the waters of the Colorado from returning to the valley. These have proved inadequate, and in 1905 and 1906 the river breaking through flowed for 18 months into the valley, forming the present Salton Sea, and in addition not only destroyed a large amount of property and land but entailed an expense of some $4,000,000 before it was again controlled and confined to its banks. Prior to and including the year 1924, more than $10,000,000 was expended for flood protection alone, and this expense continues. Each year the people of the valley are called upon to spend large sums of money for the maintenance and repair, and also the raising and extension of these levees. In addition to these expenses the annual cost for the removal of silt from their irrigating ditches and from their lands is approximately $1,350,000.

Mississippi floods in that the only way that the water could be removed would be by evaporation, necessarily taking many years for its accomplishment.

Both the Yuma and Palo Verde Projects have been also subjected to disastrous floods within the past 20 years, causing great damage to property and crops on each occasion, the last one causing over $2,000,000 damage to the Palo Verde Project alone. The Mohave Project, after large amounts had been expended for levees, was forced to abandon further work due to their inability to provide protection from the flood menace.

Mexican Situation

During the early development of the Imperial Valley the finances were limited. In order to reduce the first cost an agreement was entered into with the Republic of Mexico, whereby a canal could be constructed with its diversion within the United States but immediately passing for a distance of 60 miles through the Republic of Mexico before again returning across the boundary to the lands of the Imperial Valley. As the price for this concession by the Mexican Government, the American farmers were forced to agree that Mexican lands would be entitled to one-half the flow through the canal. With the present area under direct irrigation of 462,000 acres in the Imperial Valley and 217,000 acres in Mexico, the low flow of the river is inadequate for all. This was clearly shown in 1924, when the total flow in the river was below 1300 second feet and for 76 days every drop of water in the river was diverted. It is also apparent that under such conditions, if Mexico insists on her present plans of development and one-half of the water, then for each additional acre placed under cultivation in Mexico an acre in the Imperial Valley must

return to desert conditions unless there is storage and regulation of the flood waters.

The extremely serious situation of Imperial Valley may be appreciated by pointing out that this canal forms the only possible source of water for not only irrigation but for domestic use, and if interfered with for only a week it would mean not only financial ruin by destruction of crops, but the entire population and all live stock would have to be removed from the valley. Domestic Water

The phenomenal growth of Los Angeles and the coastal cities of Southern California since the war has resulted in such an increase in the consumption of water for domestic and commercial purposes that the limit of the available supply is dangerously close to complete absorption.

In 1906 the city of Los Angeles began construction of an aqueduct to bring water from the Sierra Nevada Mountains 250 miles away for the use of its inhabitants. At that time the population of the city was approximately 160,000. It was estimated that the aqueduct would supply a sufficient quantity of water for a population of 2,000,000 and at the rate of growth it would certainly last for many years before this population was reached. Today with a population of over 1,200,000 and with the rapid growth continuing, urgent haste is necessary in obtaining an additional source of supply. This same condition, due to the rapid increase in population, exists in the surrounding communities and cities now dependent upon the small streams available and the percolation of flood waters into the underground gravel, a supply rapidly approaching complete utilization.

With this urgent necessity in mind, these cities, including Los Angeles,

have made careful investigation as to the available sources of additional supply and find that the Colorado River furnishes the only source of sufficient magnitude to meet their necessities for an appreciable length of time. Filings have been made for the appropriation of 1500 second feet for domestic use in the cities above mentioned, and the formation of a metropolitan water district to finance the proposed $150,000,000 aqueduct project for carrying this water from the Colorado to the coastal plain cities has been formed. The city of Los Angeles has voted and expended nearly $2,000,000 on preliminary engineering rights of way. Government Recognizes Necessity

Due to the magnitude of the project necessary to furnish relief from the flood menace and to provide the necessary storage and regulation of the flood waters as well as the large quantity of silt, appeal was made to the United States Government for assistance. That the problem demanded solution and immediate action by the Government was very clearly stated by Dr. Hubert Work, Secretary of the Interior, in his report to the Committee on Irrigation and Reclamation of the House of Representatives, on March 17, 1924, when he said:

The Colorado River has been under observation, survey and study, and the subject of reports to Congress since the close of the Civil War. More than $350,000 have been expended by the Bureau of Reclamation since the Kinkaid Act of May 18, 1920. More than $2,000,000 have been expended by other agencies of the Government. The time has arrived when the Government should decide whether it will proceed to convert this natural menace into a national resource.

Government Plans for Relief

As indicated by the Secretary of the Interior in his report referred to above,

the United States Government has expended large sums of money in an investigation looking toward the best solution of the problems comprising flood and silt control, storage and regulation of flood waters for irrigation and domestic uses. The first and preliminary report made public was the so-called Fall-Davis Report published as Senate Document 142, 67th Congress, 2nd Session. The latest and most comprehensive report is the Weymouth Report to the Secretary of the Interior dated February, 1924, together with the supplemental report of June, 1924. This report incorporates a careful analysis and study of the resources and possible development of the entire river below the junction of the Green and the Colorado River.

Complete development, under the comprehensive plan thus determined, of which the proposed Boulder Canyon Project is a part, will result in the minimum amount of water lost by evaporation from the storage reservoirs and the maximum amount of hydroelectric power equaling 6,800,000 horsepower of peak capacity. The report shows further, that the first logical step in the program and the one providing the maximum amount of relief in the immediate crisis would be the building of the proposed dam in the main stream of the Colorado at the lower site of the so-called Boulder Canyon Storage Project, approximately 30 miles east of Las Vegas, Nevada; the river at this point forming the boundary line between the states of Arizona and Nevada.

CHARACTER OF PROJECT

General Description

The Boulder Canyon storage location furnishes one of the most remarkable dam sites in the United States as the walls rise abruptly to a height of

approximately 1000 feet, forming a narrow gorge. The foundation rock is admirably suited in every way for the construction of such a structure. It also provides a natural reservoir site which could, if necessity should demand it at any future time, provide a storage capacity of perhaps twice that now contemplated. The present plan of the Reclamation Service calls for a dam 550 feet in height above the low water level of the river, which would impound in the storage reservoir approximately 26,000,000 acre feet of water. With bed rock of approximately 110 feet below the present low water of the river, the total height of the dam structure will be 660 feet, a material increase over the highest dam now in existence. The tentative design as prepared calls for a structure of the gravity type arched up stream, a length at the foundation of 275 feet at the present low water line and across the top of the dam of 1100 feet.

Although such a structure is a new adventure in magnitude of design, it is well to remember that the engineers of the Reclamation Service who will build the dam under Government plans have also designed and built not only more dams than any other organization in the United States but practically all of the larger ones. Careful investigation has been made as to the type of structure and estimates prepared on the cost for both rock fill and concrete designs. Adequate spillways will be provided by means of tunnels through the rock wall on the Arizona side to a small side canyon which enters the river a short distance below the dam. The cost of a 550-foot dam complete is estimated to be $41,500,000 exclusive of interest during construction.

Hydro-Electric Power

The United States Reclamation Service, in its early conceptions of the plan

for the proposed Boulder Canyon Project, realized that there would be incident to the Project an opportunity for the development of a large block of hydro-electric power. Investigations as to probable power market were made and resulted in ample assurance that conditions were such that there would be a market for the power and that the revenue from that source would be sufficient to repay the Federal Government for its total investment in the Project, over a period of years, with interest, and also the cost of operation and maintenance.

Accordingly, the Secretary of the Interior has caused to be written into the proposed legislation alternative methods of providing for revenue from the power. One plan contemplates that the Government itself build a power plant of approximately one million horsepower installed capacity. The average or firm horsepower, if generated continuously day and night through the year, would be approximately 550,000 horsepower, hence a one million horsepower generating plant would carry peak loads during the hours of heavy demand such that the average load would be 55 per cent of the peak; that is, the power would be developed on a 55 per cent load factor.

The investigations and reports referred to estimate the cost of the power plant to be $31,500,000, exclusive of interest during construction, and it is proposed that the Government sell the power at the switchboard of the power plant at a price that will cover the cost of operation and maintenance and the repayment to the Government of the cost of the storage and power project combined over a period of years, with interest. The plan, therefore, contemplates that the Federal Government would loan its credit but be fully reimbursed for its investment, with interest, and the proposed legisla