The Central Arizona Project

CENTRAL ARIZONA PROJECT

This expert article was originally published in The Reclamation Era, and is reproduced with permission.

Before the dawn of the Christian Era, man first joined battle with the forces of nature in an effort to subjugate the unruly streams of Arizona.

This was a battle to water fertile desert waste lands and to nurture a verdant oasis in a region where the climate is such that under natural conditions only the hardiest of desert vegetation can survive. Down through the ages the battle has raged as step by step man has constrained the rivers to flow according to his will and has carved an irrigated empire from the desert. The tide of battle has varied. At times in ages past it has appeared that man's beachhead would be lost entirely and that the desert would reclaim its own forever. At times man has infiltrated far into the enemy territory only to be driven back by the relentless forces of drought.

Today this battle is approaching a crisis. Man has reached a high tide in his efforts to expand his agriculture. However, once again the forces of nature are gathering for a counteroffensive. Man must retreat or fight. Today man fights with weapons never before available. He has developed engineering methods to the point where it is in his power to build developments which would consolidate his present gains for virtually all time.

The Bureau of Reclamation points out these facts in a recently completed report on the Central Arizona project, which reveals that development of this area was begun centuries ago by a people known to us as the Hohokam. At several places in the valley today, a few canals and laterals built by these prehistoric farmers may still be found.

Investigation shows that, all told, something like 250,000 acres were cultivated by these ancient peoples in the course of their existence here. Of course, their irrigation system was rudimentary. Diversions were made by crude brush dams laboriously laid across the river. Between-season storage was unknown.

Despite their crude methods, these farmers had probably the highest-developed economy in North America at that time. They grew their own food and stored it for the future. They raised cotton and wove it into cloth. Socially and economically, they were far advanced in comparison to their wandering neighbors who lived by hunting and pillaging.

These first Gila River Valley farmers disappeared from the valley centuries ago, leaving only crumbling adobe ruins, potsherds, and remnants of their canals overgrown with desert brush and cactus.

Spanish conquistadores, searching for the famed Seven Cities of Cibola, entered the Gila River Valley in the second quarter of the Sixteenth Century and found the Papago, Pima, and Maricopa Indians irrigating their lands by diversions through canals in much the same manner as these prehistoric farmers. Jesuit Missionaries followed the early explorers and reportedly aided the Indians' agriculture by giving them new varieties of grain and vegetables. But nearly two centuries were to pass before the present agricultural industry of central Arizona became to take shape.

Today's irrigated empire was born shortly after the Civil War when settlers cleared and extended one of the prehistoric Indian canals. The first rich harvests of these desert wastelands were not easily reaped. Depredations of the notorious Apache renegades served to discharge all but the most determined settlers. The mystic lure of easy wealth in California proved far more enticing to many than the prospect of a continual struggle for water in Arizona.

Water to serve the thirsty lands of this new empire was obtained by diverting the unregulated stream flow. During the spring months, when the crops did not need much water, flood after flood boiled down the river channels sweeping away diversion dams, demolishing ranch houses, and destroying lowland farms. When the burning heat of the desert sun scorched the earth there was frequently little more than a trickle of water to serve the parched crops.

Despite these difficulties, the irrigated areas increased year by year. By about 1880 irrigation along the Gila and Salt Rivers was approaching the maximum that could be sustained by the perennial flow. However, the settlers of those days had no way of knowing what this maximum figure might be. Encouraged by past successes and urged onward by a series of years in which the run-off was greater than normal, this maximum was reached and exceeded.

Then came drought. Day after day, month after month, and year after year, the anxious farmers waited in vain for the life-giving rains needed to replenish their depleted streams. Despair invaded the homes and hearts of these people and it seemed that this new agricultural empire was doomed.

The answer to the problem was obvious. Reservoirs were needed to conserve the spring floods for use during the summer. However, no one individual or company was in a posi-tion to construct developments of such magnitude. The answer lay with the Federal Government. Realizing this need, the farmers of Arizona played an important part in obtaining pass-age of the Reclamation Act of 1902.

age of the Reclamation Act of 1902.

Floods of 1904 and subsequent years forestalled the immediate threat of drought. However, this relief was recog-nized as merely a temporary abatement and the havoc wrought by the drought-breaking floods of 1904 served to emphasize the need for harnessing these waters.

These pumped waters were discharged into canals and re-used to irrigate additional lands. Irrigation by pumping proved to be such a profitable undertaking that wells were drilled with ever-increasing rapidity throughout the area. The water thus obtained was used to serve the ever-expanding irrigated area.

On this basis new acreage was continually being brought under cultivation. Some of this area was watered by surface flows, some by pumped water, and some by a combination of both.

However, beginning the early part of the 1930's, a condition was arising which was to have serious repercussions. A few farsighted citizens saw a specter reappearing on the horizon and foretold disaster but many refused to heed the warnings. Once again the ogre of drought was coming.

Many felt that even though such was the case there was no cause for alarm because water shortages could be supplied by pumping. Underground waters were believed to be virtually inexhaustible. People held firm to the concept of vast underground rivers pouring endlessly to the sea and proceeded to develop more land.

The seriousness of the situation was not generally realized until 1940 when virtually all of the surface reservoirs throughout the central part of the State of Arizona were emptied. An economic disaster seemed imminent. Fortunately the winter of 1940-41 was one of the wettest during the recorded history of the area. Reservoirs were filled and disaster was again forestalled. Some persons believed that the floods of 1940-41 solved the water problem of the area.

However, many residents realized that the flood period merely served to temporarily abate a serious problem.

Once again the content of reservoirs in Arizona has dropped to a dangerously low level. Unless abnormal runoff occurs within a very few months Arizona once again will be faced with economic disaster. Groundwater storage will serve in some degree to alleviate the present drought. But recent experience has proven that wells in this area do not draw from an inexhaustible supply. On the contrary, the groundwater reservoirs underlying central Arizona have very definite capacities and yields. It has recently become increasingly evident that withdrawls from these reservoirs greatly exceed the inflow. The groundwater budget is out of balance. The pump lifts in this area are increasing with alarming rapidity. Unless some steps are taken to forestall such an occurrence, the time will come when the surface reservoirs will again be empty and the underground water storages will be too depleted to maintain sustained overdrafts.

There is a third though more obscure problem arising to threaten the irrigated agriculture of central Arizona. That is the problem of salt accumulation. It has been estimated that water diverted each year to irrigated lands in this area contains approximately 846,000 tons of salt. Salt outflow from these lands is but a fraction of this amount. Tremendous quantities of salt are remaining in the area and accumulating in the soils and groundwaters.

Mild concentrations of salts of this nature are not deleterious to crop production. However as salts in the soils and groundwaters become more concentrated they become increasingly toxic to plant life. Ultimately enough water must be released to permit sufficient salts to flow out of the area to prevent accumulation in the soils and groundwater. The net effect of this release will be to decrease the water supply available to the agricultural lands.

Unless remedial measures are taken, over one-fourth of the cultivated land in Arizona must revert to desert waste if the remainder is to receive a full water supply. The effects of such an enforced retrenchment would be varied. To some families it would mean displacement-a revival of the jalopy caravans which carried human flotsam away from another drought while dust blotted out the sun over Kansas. Other families would not leave, but would stay on the fight desperately for subsistence. Every family in the State would feel the effects of such a catastrophe and even State boundaries would not restrain the impact of lost production.

It is only recently that the seriousness of this situation has been fully realized. However it is now generally acknowledged that Arizona must find some source of additional water to supplement the supply available to her irrigated lands. The Bureau of Reclamation first began to study this problem in 1940. These studies were interrupted shortly after the advent of World War II and were not resumed again until 1944. At that time the State of Arizona appropriated $200,000 to be used by the Bureau of Reclamation on a cooperative basis to study the water resources of the State and their potential development.

It was readily apparent that stabilization of central Arizona agriculture would necessitate development of some new source of water. Under present conditions the Gila River and its tributaries are virtually fully developed. The entire southern part of the State of Arizona is drained by the Gila River and its tributaries. The extent of development along those streams may be appreciated when it is realized that for the past 7 years the mouth of the Gila River has been completely dry. The only source of supply adequate to solve the water problems in Arizona is the Colorado River.

Diversion of this stream to the central part of the State had been proposed and considered for a quarter of a century prior to the beginning of investigation in this area by the Bureau of Reclamation. Various groups and individuals had proposed numerous alternative projects whereby Colorado River water could be diverted to the central part of the State. However most of these plans were somewhat nebulous. Hampered as they were by inadequate funds, the various individuals and groups had been unable to conduct the necessary investigational work.

Having determined that importation of Colorado River water was essential to solution of the water-supply problems in central Arizona, the Bureau of Reclamation undertook to ascertain which was the most feasible route for bringing this water into the State. Analysis of the situation indicated that every reasonable route had been suggested at one time or another. With the data which were available at the time, the Bureau of Reclamation undertook to determine which might be the most feasible plan. These data were admittedly inadequate and in many cases inaccurate. However, sufficient data were available to permit the elimination from further consideration of some plans for diversion which were materially less feasible than others. From the results of these first studies the Bureau of Reclamation determined that three routes remained which should be analyzed in greater detail.The Bureau undertook to obtain field data to the extent necessary to make a selection among the three alternate routes.

Selecting the best of these routes proved to be a difficult task. On the basis of studies outlined in a report issued in September 1945, it was possible to narrow consideration to two routes. However, it was not until February 1947 that a report was issued covering studies which supported the recommendation that all further studies be confined to the Parker Route.A short time prior to this recommendation. Senator E. W. McFarland, of Arizona, submitted to the Senate a bill to authorize construction of the Central Arizona project. In June and July of 1947 the Irrigation Subcommittee of the Senate Public Lands Committee held hearings to consider this project. At those hearings it was decided that the Bureau should proceed with the studies which were then in progress and submit to the committee a more detailed report on the project.

Such a report has been prepared and recently released by Secretary of the Interior J. A. Krug.

The primary purpose of the Central Arizona project would be to deliver supplemental water to approximately 640,000 acres of land now irrigated with an inadequate or insecure water supply or formerly irrigated, but now idle for lack of water. However, the project would serve many additional purposes. Almost 41/2 billion kilowatt-hours of electric energy would be generated each year by the Central Arizona project. Slightly less than one-third this amount would be used to operate project pumping plants. The remainder would flow to the kilowatt-hungry power market of the great Southwest. Features of the project would be located in four States, and thus would directly affect the daily lives of literally millions of people. The users of irrigation water, municipal water, and power, the fishermen, the vacationists, all these and many more would use the project directly.

Full development of the Central Arizona project would involve construction of: Bluff Dam on the San Juan River; Coconino Dam on the Little Colorado River; Bridge Canyon Dam on the main stem of the Colorado River: the Havasu pumping plants near Lake Havasu: the Granite Reef Aqueduct extending from Lake Havasu to the Granite Reef Dam: the McDowell pumping plant; the potential McDowell Dam on the Salt River; the Salt-Gila Aqueduct; Buttes and Hooker Dams on the Gila River; the Charleston Dam on the San Pedro; and a pipe-line to the city of Tucson. The project also contemplates improvement of the irrigation system in the Safford Valley and enlargement of the existing Horseshoe Dam. In addition, an irrigation distribution system, an irrigation drainage system, and a power transmission system would be required and provided for under the project plan of development.

At first glance many of the features contained as a part of the Central Arizona project may seem unrelated. Consideration of these various features individually is needed to see the inter-relationship which each bears to the other and to the project as a whole.

Bridge Canyon Dam on the Colorado River would be located at the upstream end of Lake Mead. Its prime purpose would be to provide energy for the Parker pumping plants. It would, in addition, provide a large block of electric power for commercial sale. The revenue thus derived would represent a sizeable portion of the income necessary to repay project costs. Bridge Canyon Dam would be approximately 740 feet high, 80 feet higher above tail water level than Hoover Dam and requiring 75 percent more concrete.

Despite its height, Bridge Canyon Dam would create a relatively small reservoir of approximately 3,700,000 acre-feet which is only a little more than 10 percent of the capacity of Lake Mead. At the present time well over 100,000 acre-feet of silt passes through the Grand Canyon every year. Such a slit inflow would soon encroach on necessary storage capacity in Bridge Canyon Reservoir, unless some provision were made to prevent such an occurrence. In addition, because of the small available capacity it would be highly desirable to provide upstream flood control and river regulation.

For the foregoing reasons two upstream dams have been considered as essential adjuncts to the Bridge Canyon Dam. Bluff Dam, furtherest upstream of these, is on the San Juan River. This structure would be tri-purpose in that it would serve to detain silt, control floods and provide river regulation in addition to incidental uses. Although it is a small unit in the Central Arizona project it would be a sizeable feature in its own right. It would have a height of 340 feet and a reservoir capacity of 3,000,000 acre-feet. Coconino Dam on the Little Colorado River would serve the dual purposes of silt detention and flood control. The reservoir thus created would be slightly larger than the lake impounded by Roosevelt Dam which was built as the first unit of the Salt River project shortly after the turn of the Century. Coconino Dam would be approximately 20 feet lower than Roosevelt.

Granite Reef Aqueduct. Diversion of Colorado River water would be accomplished by pumping from Lake Havasu into the potential Granite Reef Aqueduct. Four pumping plants to be installed along the western end of Granite Reef Aqueduct would lift the water a total of 985 feet. By way of comparison, the Colorado River Aqueduct of the metropolitan district of southern California involves pumping a total of 1,617 feet.

Granite Reef Aqueduct would transport water from Lake Havasu to Granite Reef Dam. It would have a total length of 241 miles. The westernmost 25 miles of the aqueduct would be located in extremely rugged mountain terrain. The remainder would pass through typical desert country occasionally skirting small mountain ranges and crossing a few major drainage channels such as Cunningham Wash. Centennial Wash and Hassayampa, Aqua Fria and New Rivers. By far the major portion of the aqueduct would be open canal. However, siphons would be provided as necessary.

Studies have revealed that maximum efficiency demands that Granite Reef Aqueduct be designed to operate at a continuous rate of flow as now considered. The capacity of the aqueduct has been adopted as 1,800 cubic feet per second. Diversions from the Granite Reef Aqueduct would serve lands in the northern and western parts of the project area.

The aqueduct terminus would be in the diversion pool behind the existing Granite Reef Diversion Dam. Since delivery would be made at a constant rate through the Granite Reef Aqueduct there would be times when the deliveries would exceed the requirements. McDowell Pumping Plant. At such times, delivered water would be lifted 88 feet by the potential McDowell pumping plant and delivered by a short canal to the McDowell Reservoir for retention until months of high irrigation demand. The potential McDowell Dam would also regulate floods and provide for some additional regulation of Salt and Verde River flows.

A Power Plant at the McDowell Dam Site would generate electrical energy for the commercial market. McDowell Dam, itself would be relatively low, having a maximum height of only 131 feet. The reservoir thus created would impound more than half a million acre feet.

McDowell Reservoir would inundate the intake for the Phoenix Municipal Water Supply System. This intake would be placed by a pipe line connecting the reservoir to the existing city aqueduct. A filtration and softening plant would be constructed to insure the city of a continuous supply of water equal in quality to that now utilized.

Enlargement of Existing Horseshoe Dam. To obtain the maximum practical utilization of existing water supply within the Central Arizona Project area the over-all plan of development would provide for enlargement of the existing Horseshoe Dam. The Horseshoe Reservoir now has an active storage capacity of approximately 68,000 acre-feet. Increasing the dam by 40 feet in height and installing spillway gates would permit storage of water to the extent of 298,000 acre The miracle of irrigation in the arid land has resulted in the growth of Phoenix, in the heart of Arizona's great Salt River Valley.

feet. This additional capacity would serve to capture the major portion of the Verde River flood water which now spills uncontrolled over Granite Reef.

Installation of a Power Plant at the Horseshoe Site would permit utilization of Verde River flows for power generation.

Salt-Gila Aqueduct. Assuming Colorado River water could be exchanged for Salt River water it would then be possible to serve irrigated lands in Pinal County with water diverted from Salt River at Stewart Mountain Dam. Delivery of this water would be accomplished by the Salt-Gila Aqueduct. This aqueduct would also consist primarily of open concrete-lined canal. A few short tunnels would be required in the northernmost end of the aqueduct to transport the water through the exceedingly rugged terrain which lies along the south bank of the Salt River. Major siphons would be required at Queen River and the Gila River. The total length of the aqueduct would be 74 miles. Its capacity has been adopted at 1,275 cubic feet per second. As currently conceived the aqueduct would terminate in the Picacho Reservoir south of Coolidge. Diversion would further be accomplished by a distribution system emanating from Picacho Reservoir.

Buttes Reservoir. Water delivery through the Salt-Gila Aqueduct would not only provide for the supplemental requirements of the area but also would provide additional water to be used as a basis for exchange to permit increased upstream diversion. In line with the policy of making a full development of the existing water supply the Central Arizona project would involve construction of a dam at the Buttes site. This dam would be virtually the same height as the existing Roosevelt Dam and would also provide for generation of power. Buttes Reservoir would control and conserve the flood water of the San Pedro and tributary washes entering the Gila River below Coolidge Dam. It would also impound silt which is contained in large quantities in the waters which are now diverted to the irrigated lands during the summer months. and which present a serious problem to farmers of the area.

Charleston Dam. With water from the Salt River provided to lands in the middle Gila area as a basis for exchange, construction of a dam at the Charleston site on the San Pedro River could be accomplished without infringement on the rights of downstream water users. This dam would be located about one-half mile north of Charleston, Arizona. It would provide flood control for the protection of downstream developments. In addition, it would regulate the erratic flows of the San Pedro River, and facilitate diversions to lands now irrigated along the river.

Tucson Aqueduct. In addition, the Charleston Dam would serve as a diversion structure for the Tucson Aqueduct. The Tucson Aqueduct would consist of approximately 70 miles of closed conduit through which water would be conveyed to the city of Tucson. As a part of the aqueduct, a pumping plant would be installed to lift the diverted water 300 feet for delivery to Tucson.

As a part of the Central Arizona project, certain developments above San Carlos Reservoir would be required to meet the needs of the upstream irrigated areas. Numerous plans of development have been proposed for these upper lands. In general, there appear to be four areas in need of additional development, namely, the Safford Valley; the Duncan-Virden Valley; the Red Rock Valley; and the Cliff Valley.

The Safford Valley improvements would be built to conserve and utilize the existing water supply to best advantage. A permanent diversion structure at the upper end of the Safford Valley to supply a high-line canal would be included as a part of this development. A high-line canal would extend along the south side of the valley, and a branch canal would cross the Gila River near Safford to serve the north side. Pumps for the development of groundwater, to supplement available surface water, would be installed as part of this development.

Construction of a dam at the Hooker site, on the upper Gila River, about 7 miles northeast of Cliff, N. Mex.. is considered as a potential development to serve requirements upstream from the Safford Valley. Such a structure would provide flood control and silt retention and eliminate serious problems for downstream irrigators. It would also regulate the flood flows of the river, for use at a time when the normal flow of the river would be insufficient to meet irrigation requirements. Lands in the Cliff Valley, the Red Rock Valley, and the Duncan-Virden Valley would all be benefited by this regulation.

Irrigation Distribution System. Some of the districts included under the Central Arizona project maintain their own

ROBERT MARKOW

Where water is brought to the desert green fields and productive acres are the result. The rich land needs only water.

distribution systems. However, many of these areas which are irrigated by pump water do not. In addition, some areas irrigated by surface water have inadequate distribution facilities. Under the Central Arizona project, an irrigation distribution system would be designed to deliver water as required.

Irrigation Drainage System. Despite water shortages throughout the major part of the Central Arizona project, some of the lower lying lands are faced with the problem of water-logging. The Central Arizona project would include an irrigation drainage system to prevent water-logging, and to remove excess dissolved salts from the area. Open gravity drains would be used where possible. Additional drainage as required would be accomplished by pumping from wells.

Power Transmission System. Under this project a power transmission system would be needed to convey power from Bridge Canyon power plant to the Havasu pumping plants, and from the various power plants throughout the project to the power market areas. In discussing these various features, the primary purposes of each have been outlined. In addition to those enumerated, each of the features would have secondary purposes, or incidental benefits, which are of considerable importance.

Recreation Facilities. In an arid country, such as that in which the Central Arizona project is located, the importance of lakes for recreational uses is of far greater significance than commonly realized by residents of more humid climates. Fish and wildlife propagation would be another important purpose served by all the reservoirs to be created under the Central Arizona project.

The Central Arizona project is an enormous development. On the basis of costs prevailing in April 1947 it would cost approximately $738,400,000 to construct the features which we have just discussed. In recommending that this vast project be authorized, Secretary Krug has concurred in the recommendation of E. A. Mortiz, Regional Director of Region III, under whose direction the report was prepared. This recommendation is not, however, unqualified. Mr. Moritz has pointed out in his recommendation that there is a controversy between Arizona and California for the amount of water legally available to Arizona from the Colorado River. If Arizona's contentions in this controversy are correct, it will be legally possible for Arizona to divert 1,200,000 acre-feet of water each year. However, it is California's contention that there is no water available for such purpose. Mr. Moritz points out that the Bureau is not authorized to resolve this difference, but takes his opportunity to point out and assumes that Congress will give due consideration to the matter of water rights.

The report points out that the project cannot repay the reimbursable costs which would be charged against it under the Secretarial authorization provisions of Reclamation Law. However, the report sets forth certain repayment provisions which, if applied to the Central Arizona project, would make it possible for the development to repay its obligations. In general these provisions would require repayment of reimbursable costs, within 78 years, from revenues derived through the disposition of irrigation water, municipal water and electrical energy. Funds spent for constructing power features would be repaid at 2.5 percent interest on the unpaid balance. Costs allocated to irrigation would be interest free. Project costs allocated to flood control, silt control, recreation, fish and wildlife propagation, and salinity control, would be nonreimbursable.

The report states that project revenues are based on a charge of $4.50 an acre-foot at the farm headgates for irrigation water developed by the project; 15 cents a thousand gallons for municipal water at the city storage reservoir; and 4.8 mills a kilowatt hour for electric energy delivered at the load centers. The total revenue from those three sources would be sufficient to repay the reimbursable construction costs.

The report further recommends that the State of Arizona enact an adequate ground-water code to limit the pumping from the ground-water in the project area to the safe annual yield; and establish an organization in form and with powers to tax properties within the project boundaries and to contract with the Government for payment of costs allocated to irrigation and municipal water supplies.

These are but recommendations dependent upon the will of the people and the final authorization of the Congress of the U. S. Should they become realities, the Bureau of Reclamation may soon undertake what may be the final stage in development of the irrigation potentialities in central Arizona.