Development of the Colorado River: The Justification of Boulder Dam
THE Colorado is one of the largest and most notable drainage basins of the United States. It drains the major portion of the Rocky Mountain region, and has an area of 244,000 square miles. The basin is divided rather sharply by nature into three main regions. The upper or mountain region, which furnishes large precipitation and most of the water for the system, reaches altitudes above 14,000 feet, and lies mainly in Wyoming, Utah, Colorado, and New Mexico. These are called the states of the upper basin. Arizona is a state of the lower basin, but also contributes the waters of the Little Colorado, most of the Gila, and some smaller streams. Nevada contributes less water than Arizona, while California contributes still less, but has large areas of land upon which water has been applied and to which rights have accrued.
The mountain regions around the sources of the Colorado merge into a second and more arid region in which the river cuts profound canyons, through which it runs at elevations too low to be diverted on any of the adjacent lands. The river emerges from these canyons where it forms the boundary between California and Arizona, and below this point is the third division, containing wide rich valleys favorable for irrigation, with a very arid and semitropic climate.
Most of the water comes from the upper reaches and, flowing through the canyons, has a fall of thousands of feet, which furnishes opportunity for the development of vast quantities of power. As the tributaries of the river leave the high mountain regions, they are usually clear and limpid; but as the branches unite, and thus concentrate the volume of water, the high velocities induced by the rapid fall in the canyons cause rapid erosion. The river grinds the rocks into gravel, the gravel into sand, and the sand into fine silt, gradually accumulating large quantities of sediment, and, according to estimates, carrying an average of over 100,000 acre feet of mud to the ocean every year. This is discharged into the Gulf of California, which formerly headed a hundred and fifty miles farther north than its present boundary.
The river, flowing for millions of years, loaded with sediment, gradually built a delta across the Gulf at its mouth and cut off the northern end of the Gulf, leaving an inland sea which, in that arid region, gradually evaporated and formed a depressed valley, the bottom of which is about three hundred feet below sea level. This great valley extends from the foot of the mountains north of Indio southward across the Mexican line, and comprises over two million acres, mainly of rich agricultural alluvium, the larger part of which is in Mexico. The name of ‘Imperial Valley,’ given to this region, is expressive of its vast extent and fertility.
Lying between the northern end of this valley and the valley of the Colorado River is a ridge of sand hills several hundred feet above the valley, gradually declining in elevation until it terminates south of the Mexican line. About the year 1900, the Colorado was diverted near the point where it leaves the United States and carried through artificial and natural channels to irrigate the Imperial Valley in California. In reaching this point it passes through about sixty miles of Mexican territory.
The richness of the Imperial Valley has led to rapid development, and there are now nearly 500,000 acres of land under irrigation, devoted largely to winter vegetables and citrous fruits.
The diversion of the river was accomplished with American capital, by a company incorporated in Mexico, and under a concession from the Mexican Government which allows the water to flow through Mexican territory on condition that one half of the amount so flowing shall always be available for use on Mexican lands. This concession from Mexico to a Mexican corporation has no binding effect on the United States.
About 200,000 acres are irrigated from this canal in Mexico, and, under the concession, this is given half the low-water flow of the river. The agricultural development has reached the point where, in the low-water season of the late summer and fall, there is insufficient water in some years for the land under cultivation; and, under the concession, more than half of this is taken in Mexico, leaving the losses to be sustained by the American farmers who have borne all the financial burdens of water diversion and flood protection. The crop losses from this cause have been very heavy. In addition to this, the Mexican authorities frequently hamper the work of repair and flood protection by onerous tax levies and irritating restrictions. These, with the recurring shortages of water, — which will become greater as the Mexican development proceeds, — have produced an acute condition which has halted the development of the Imperial Valley, and threatens the safety of the farms already cultivated.
A still greater hazard to the Imperial Valley is the persistent growth of the Colorado Delta, by which the river is building up its channel by the deposit of sediment at the rate of one foot of altitude per year. It is flowing on a ridge south and east of the Imperial Valley, and the farmers have provided a long, high levee to prevent its overflow into the valley. As the river is progressively building up its channel, this protection is temporary and precarious.
In 1905 the river broke through the protection works and poured in flood volume into the bottom of the Imperial Valley, known as Salton Sea, and cut deep channels in the alluvium between the Mexican line and the Salton Sea. About 40,000 acres of excellent valley land were thus destroyed, including a large number of farms, numerous houses, and some lives. After nearly two years’ effort, this flow was stopped, the river was forced to the southward into the Gulf of California, and levees were built to prevent the recurrence of the menace; but as the river is continually building up its channel with the accumulated sediment, it may, at any flood season, break over its barriers and again flow into the valley. With the channels already cut, and with the increased elevation of the river, this flow will be nothing less than torrential during flood season, and it will be impossible to stop it until the low-water season, and very difficult then. Two seasons of maximum discharge would flood the valley and destroy 10,000 farms and practically all of the development in the valley. The people would be rendered homeless, and the valley could not be drained, because it is below sea level. The slow process of evaporation would be necessary to restore the valley even after the river had been controlled, and for purposes of the present generation the valley would be annihilated. Unless flood control through storage is provided, this catastrophe is inevitable — the only doubt being when it will occur. Whether it will be five years hence, fifteen years, or twentyfive, it is a constantly growing menace with constantly growing costs for alleviation.
Realizing this situation, President Roosevelt in 1906, in a message to Congress, emphasized the necessity of permanent Colorado River control and development work. During the past twenty years the farmers of the Imperial Valley have annually expended large sums of money building levees and controlling the flow of the river.
In 1920, owing to the acute situation, Congress enacted what is known as the Kincaid Act, authorizing a detailed survey and study of the lower Colorado River, with a view to finding a permanent solution of its flood problem. The study was entrusted to the supervision of the author hereof, who had been conducting investigations of the entire Colorado River basin for over twenty years. These studies, so far as related to the lower Colorado, were collected and digested, and an intensive investigation made of the water and flood problem of the Imperial Valley. The results of these studies were submitted to Congress in 1922, and were published as Senate Document No. 142.
It was recommended that the Government construct a dam about 555 feet high in Boulder Canyon on the Colorado River. This would form a reservoir of 27,600,000 acre feet capacity at the lowest point on the river where such a storage could be secured. It would be large enough practically to control the entire flow of the Colorado River, regulating it for supplying the deficiency of irrigation water in the Imperial Valley and for extending this over large areas of public land adjacent to the present irrigation district.
To avoid recurring conflicts with Mexico and to reach higher lands not commanded by the present canals, it was recommended that the Government construct, entirely within the United States, a canal leading from the Colorado River into the Imperial Valley, to be paid for by the lands benefited.
In addition to the control of the floods and the regulation of the river for irrigation, the dam proposed would furnish the head and regulate the water supply to an extent sufficient to develop about 600,000 continuous horse power of hydroelectric energy. With the growing demand for power in the Southwest, it has been shown that this amount of power would be absorbed within three or four years after its development, and would yield a revenue sufficient to amortize the cost of the dam and power plant within forty or fifty years.
The recommendations of this report are in the main embodied in the provisions of the Swing-Johnson Bill, recently passed by Congress and approved by President Coolidge on December 21, 1928.
Municipal Water Supply
In addition to the flood menace, the irrigation demand, and the power asset, the Boulder Dam, by regulating the river and settling out the silt, will furnish a supply of water to the municipalities of Southern California, which are rapidly developing an acute need of such a supply. That district has nearly exhausted its local supplies, obtained by storage and by pumping from underground, and these sources have been so depleted by overdraft that this region must seek a new, distant supply or shut down abruptly upon further development.
The cities of Southern California have for years been seeking state authority to combine in a workable district to finance and build a connection with the Colorado River in order to furnish a municipal supply for the future. The necessary authority was obtained at the last session of the State Legislature, and the Metropolitan Water District now has a legal existence, twelve cities having voted by large majorities to join and other cities legally eligible now preparing to join.
The conduit for carrying water to these cities will be a prodigious structure over 260 miles in length, with 50 miles of tunnels, and pumping lifts aggregating about 1300 feet to raise the water to the tunnel through the Coast Range. This aqueduct will create a large demand for power, which will furnish a considerable portion of the market for the Boulder Canyon development, thus assuring its success to that extent. In fact, municipalities of Southern California have agreed to subscribe and become responsible for the purchase at its estimated price of all of the power to be developed at Boulder Canyon beyond that taken by other customers. The responsibility of these municipalities is beyond question and gives convincing assurance of the financial solvency of the undertaking so far as the Boulder Dam is concerned.
Other Dam Sites
The Grand Canyon of the Colorado is a profound gorge cut in the various formations of the great Kaibab Plateau, and is a continuation of Marble Canyon, which begins at Lee’s Ferry, near the Arizona line. These canyons of the Colorado, and the canyons above on the river and its tributaries, contain numerous gorges which furnish favorable dam sites for the development of power; but none of them are capable of economical development to an extent approaching the storage capacity of the Boulder Canyon site as proposed. Moreover, none of them would intercept the entire flow of the river, because numerous tributaries of importance flow in below. Therefore, even if capacity were available, they would not furnish flood control with the completeness that is attainable at Boulder Canyon. This site has been thoroughly investigated by a large number of borings and careful geological investigations, supervised by eminent engineers and geologists of long experience employed for their special qualifications in these lines. No competent expert who has examined this site has any criticism to make of the physical conditions for the construction of such a dam and the provision of such a reservoir. That it will thoroughly control the floods of the river and efficiently regulate its flow for the development of power and later use for irrigation is undisputed. Nevertheless, certain objections have been advanced.
It has been argued by the opponents of Boulder Canyon Reservoir that 600,000 horse power, if developed, could not be absorbed by the available market for power for many years, and that in the meantime the interest charges would accumulate to such an extent as to make the development a failure. Finally, the matter was referred to Mr. Lester S. Ready, for many years Chief Engineer of the California Railroad Commission, and Mr. H. G. Butler, an eminent expert on power markets; and these two competent authorities, after a thorough examination of the subject, proved that if the Boulder Canyon power were immediately provided it would be absorbed within three or four years after it was produced. This estimate was confirmed after full Investigation by the consulting board appointed for the purpose by the Secretary of the Interior.
Notwithstanding this authoritative finding, the opponents are still expressing doubts as to the wisdom of so large a development and repeating their former recommendations that the river should be developed by a series of small dams.
As represented by actual schemes of construction submitted, dams have been proposed of heights, respectively, of 158, 163, 194, 209, 223, and 225 feet, in portions of the canyon where much larger development would be far more economical.
In general, the power developed by means of a low dam in the Colorado Canyon is far more expensive per unit than the power produced by a high dam. In either case, the floods of the river must be controlled to permit the excavation of foundations, which are everywhere deep. These control works cost as much for a low as for a high dam.
The same is true of the railroad that must be built to convey the machinery and materials to the site, which, in any case, is a heavy expense. This is also true of the great construction plant. The cost for a low dam would thus be relatively much higher per unit of power developed, on account of these major costs being about the same for both.
The production of power by a low dam would be less in proportion to the height of the dam, owing to the better regulating effect of the water by the wider pond produced by the high dam, and the fact that each reservoir must be provided with a margin for the rise and fall of floods without interfering with the next development above.
Careful estimates of cost, based upon extensive detailed surveys at the Boulder Canyon site, show that a dam 555 feet high, as proposed, will develop power nearly 30 per cent cheaper per unit than a dam fifty feet lower. A still lower dam would be similarly more expensive per unit of power produced, and in varying degrees the same principle applies to the development of any power site in the canyon region within the limits of feasible construction. To develop the river by a series of low dams, as proposed by the opponents of Boulder Canyon, would be fatal to cheap power. Under such a plan, power development on the Colorado River would be no longer a menace to investments in future power sites in the Sierra Nevada Mountains, for it would make the cost of Boulder Canyon power about as high as that produced in the Sierras, and it is such development as this that might be expected if it were turned over to private exploitation. This would largely destroy the great natural asset which the nation owns in the power possibilities of the canyons of the Colorado.
Cost of Power
It is being asserted that recent improvements in steam-turbine and other generaling machinery have so reduced the cost, of steam power when generated by large units as to make it lower than the estimated cost of hydroelectric power produced by the proposed Boulder Canyon Dam. These claims have been urged partly on the ground of low fuel costs in Southern California, where oil is abundant. Recent investigations, however, have disproved these claims.
In the Electrical World for October 27, 1928, arc given the results of detailed investigations into sixteen of the largest modern steam plants in the country. The table printed below, condensed from the Electrical World, shows the total cost per kilowatt hour of power generated in each of these sixteen stations, from which it will be seen that the average cost in practice is 0.853 cents per kilowatt hour — which is nearly double the cost of delivering the electric current from Boulder Canyon Dam to the cities of Southwestern California.
Even the lowest of the costs shown in the table is substantially higher than the cost of Boulder Canyon power. The first plant in the list is the one that would be most directly in competition with Boulder Canyon power, and shows a cost nearly three times as great as the estimated cost of that power delivered to the same metropolis.
The result of the development of Boulder Canyon would be much cheaper power and the employment of existing steam-power stations for stand-by purposes and for meeting future growth. For these purposes, of course, the result would be to supersede the more wasteful of steam-power stations and preserve the cheapest and best.
The vast fuel saving which the Boulder Canyon Dam would effect is one of its major virtues, and would substantially postpone the time, now Average cost per kw. hr. (cents) 0.853 rapidly approaching, when our oil resources will be exhausted.
SUMMARY OF COST DATA ON REPRESENTATIVE POWER STATIONS
|CAPACITY KVA.||NO. OF GENERATORS||DOLLARS PER KVA.||CTS. PER KW. HR.|
|Station||Building||Equipment||Fixed Charge||Total Production||Total|
One criticism of the Boulder Canyon plan is that a high dam would produce so large a lake that the losses by evaporation would be excessive; that the reduction of the floods to a maximum of 40,000 cubic feet per second, as proposed, is not necessary, but that a reduction to 80,000 would answer. A fair summary of the argument is that it is unwise to store this water because the reservoir would lose part of it by evaporation, and that it is better to allow the floods to continue to flow to the sea unused, and to fight, them on the way by means of high levees and other expensive and perilous provisions.
The same authority, criticizing evaporation from Boulder Canyon reservoir, proposes to substitute for it a reservoir in Mohave Canyon, which would have a much larger water surface and entail about 75 per cent more evaporation in proportion to the water stored. It would also submerge the city of Needles, a large railroad hotel, roundhouse, machine shops, large icing plants, twenty-four miles of yard track, and twenty miles of doubletrack main line, and the length of the transcontinental railroad would be increased by about three miles. It would require the reconstruction of a similar length of the Santa Fe Trail Highway, and of two great bridges over the Colorado River. It would also submerge over 30,000 acres of excellent land in the Mohave Valley, susceptible of easy irrigation after the river is controlled, which could not be replaced. It is true that other areas could be irrigated with the same water, but these other areas could be reached only by very expensive canals, long tunnels and high pumping lifts, which would cost from two to three hundred dollars per acre for construction, and incur prohibitive prices for operation and maintenance. Such enterprises are not feasible now, and may never be, and while it is wise not to prejudice their future possibilities, still the argument that they justify the destruction of rich bottom land along the river is untenable and destructive of natural resources.
The dam in Mohave Canyon that would entail all of this destruction would produce very little power, because of lack of head. It would be the most expensive power site in the Colorado Canyon that is seriously proposed by anybody, involving more than double the cost per horse power of the proposed development in Boulder Canyon, aside from its enormous evaporation losses. Its construction would be a signal victory for anyone opposed to the development of cheap power on the Colorado.
The Silt Problem
The Colorado River, in its natural state, is normally a muddy stream, as indicated by its name. It carries to the sea an enormous amount of finely divided, almost impalpable silt, except when this is diverted with the water for irrigation.
The quantity of silt is so excessive as to be an intolerable nuisance in the irrigation canals. As the water is diverted into smaller and smaller channels to carry it to the point of use, its velocity is checked at various points, and it deposits portions of its sediment in the canals and laterals, which necessitates frequent cleaning of the same. It is estimated that the Imperial District expends more than a million dollars per annum in cleaning out of the canals the surplus silt which the water deposits therein. In addition, the farmers themselves spend two dollars per acre, or a million dollars per year, in cleaning laterals and farm ditches. This silt, accumulating on the banks, is building them higher and higher, and the difficulty of silt removal is steadily increasing.
The Boulder Dam will intercept all of the waters that flow in the river at the reservoir site, and the sediment will settle therein. Thus only clear water will be drawn through the water wheels and pass on down the canyon. The desilting process is a great benefit to irrigation and is absolutely indispensable for the domestic supply, so that this is one of the major benefits promised by the Boulder Canyon reservoir.
The large quantity of the sediment carried by the Colorado River naturally raises the question whether or not the reservoir will fill with sediment too soon to justify its construction.
The estimated amount of sediment passing the Boulder Canyon Dam site averages about 100,000 acre feet per annum. The capacity of the proposed reservoir is about 27,000.000 acre feet. Therefore, if all the sediment were deposited in the reservoir and none of it taken out, it would require 270 years in which to fill, and the dam would still remain a good power site, provided the river were regulated above by other reservoirs.
In order to secure the necessary head for development of power, the lower portion of the reservoir will be held permanently filled with water to about one third the capacity of the whole. This lower part is available for the storage of sediment without any depletion of the storage capacity available for irrigation and for flood control. It would require nearly one hundred years to fill this portion of the reservoir, and until that is done there would be no impairment whatever of the functions of the reservoir by sediment.
Long before the hundred years have elapsed, other dams for the development of power and other purposes will be constructed farther up the river, which will intercept all of the sediment that now passes those points, and the quantity reaching Boulder Canyon will be diminished by this amount. In all probability these developments will proceed to a fair degree of completion within the next forty or fifty years, and it will, in fact, be many centuries before the lower third of the Boulder Canyon Reservoir is filled with sediment. If desirable, this sediment can be removed by hydraulic processes by means of the power to be developed either at Boulder Canyon or at points above, and the life of the reservoir thus indefinitely prolonged without interfering with its functions in any degree.
One objection heard is the allegation that the Boulder Canyon Reservoir would be rendered unfit for irrigation or domestic use by reason of salt deposits that occur therein. This question was thoroughly investigated by an eminent geologist of the United States Geological Survey, who reported that the quantity of salt, as compared with the volume of water, was negligible, and that in any event a brief period of solution would so undermine the overlying earth that it would cave in and cover up the deposits before any injurious amount could be dissolved.
All competent experts who have examined this subject are agreed with Professor Ransom in the above conclusions, and their opinions have been duly published and made available to the public.
Glen Canyon Project
The Boulder Canyon development has been antagonized by a proposition to build a large reservoir in Glen Canyon in the northeastern part of Arizona, nearly twice as far from the markets and much more expensive in construction. Estimates of relative costs show that the development of power in Glen Canyon would be nearly twice as expensive per unit as in Boulder Canyon, and the cost of transmission to points of use would be over twice as great. The power would be much less reliable, owing to the enormous length of transmission line through country remote from construction and maintenance facilities.
The Glen Canyon reservoir would not solve the flood-control problem, because it would leave uncontrolled about 50,000 square miles of mountainous drainage between Glen Canyon and Boulder Canyon, which would cause the flood menace to be very dangerous.
Furthermore, a high dam in Glen Canyon is of doubtful feasibility, owing to the very soft and friable condition of the rock, which resembles that which failed to support the St. Francis Dam in Southern California. It is in sharp contrast to the hard, tough rock which forms the base and abutments of the proposed Boulder Canyon Dam.
Benefit to Upper Basin
The states of California, Arizona, and Nevada would benefit enormously by production of a large quantity of cheap power, which would stimulate the mining and industrial development of these regions. California and Arizona would also benefit greatly by the regulation of the floods, which would render the water available for irrigating the large valleys in those states. There is also a very great and indirect benefit which this storage would confer upon the states of the upper basin. Here there are large areas of irrigated lands, some of which have been placed under irrigation since the Imperial Valley was reclaimed and are junior thereto in the appropriation of water. Under the decisions of the Supreme Court of the United States, in times of shortage the Imperial Valley, having a prior appropriation, has the legal right to compel the closure of the head gates to the canals in the upper basin in order that the water may flow down to the senior appropriator, the Imperial Valley. These shortages are annually growing more extensive and acute, and the situation furnishes a formidable barrier to any further development of irrigation in the upper basin. Indeed, many of the projects already developed are seriously menaced as to their water rights, and this includes two projects in Colorado and one in Utah already put into operation by the United States Government, which would be deprived of water at times if the rights of the Imperial Valley were strictly enforced.
If a large reservoir were built at Boulder Canyon, the people of the Imperial Valley and the lower Colorado valleys in general would depend upon this reservoir for their supply, and would waive all rights to the natural flow of the streams above and release this for development and use in the states of the upper basin. The Imperial Irrigation District has already offered to make this exchange.
If the large enterprise such as proposed at Boulder Canyon were carried out, the appropriation of water for its development would, under normal operations of law, require the waters in future to run past this point, as at present, for the use of the development there, and thus the future diversion of water in the upper basin would be forestalled unless this right were waived.
To meet this situation, immediately after the proposal by the author of the Boulder Canyon enterprise a movement was started to secure an agreement among the seven states within the Colorado River basin concerning the division of water, and a compact was signed by representatives of all of those states and of the United States, forming the Colorado River Commission, headed by President-Elect Herbert Hoover, then Secretary of Commerce and representative of the United States upon the Colorado River Commission. This compact provided for the division of water between the two main regions into which this river system is divided — the upper states, composed of Wyoming, Utah, Colorado, and New Mexico, where most of the waters rise; and the lower division, consisting of Nevada, California, and Arizona. This compact provides in a general way for the equal division of the water at Lee’s Ferry, near where the river leaves the upper states and enters the lower states, and gives the lower states, in addition to one half of the waters of the main stream, all of the yield of its tributaries below that point. It virtually leaves the upper states untrammeled in their development, both for power and for irrigation, and leaves the lower states an abundance of water for the development of power and of the irrigable lands adjacent to the river, and also for municipal supplies.
The recent legislation provides that at least six of the seven states shall ratify this compact before the legislation becomes operative. It also provides that the executive officer of the United States must secure firm contracts for the purchase of sufficient power to ensure the financial solvency of the project before the money is spent. Thus the financial end is carefully guarded, and safeguards against injustice to any portion of the basin are furnished by the recent legislation, which removes any valid objections that might be raised on these points.