Omar Turney Hohokam Canals

Dr. Omar Turney (November 1, 1866 – December 21, 1929) was an American archaeologist and engineer. He had been employed beginning in 1888 as an assistant engineer on the rebuilding of the Arizona Canal Dam. And was later employed as a surveyor for the Santa Fe, Prescott and Phoenix railway. He also served successively in the United States geological survey and in the United States reclamation service. He was one of the principal sponsors of the Roosevelt Dam, and is largely responsible for the name given to the Dam. For 12 years after leaving the government service Dr. Turney served the cities of Phoenix, Mesa, Tempe and Glendale as city engineer.

In his last year of life Dr. Turney published a series of articles in the Arizona Historical Review entitled “Prehistoric Irrigation“, the result of the collection of data over a period of more than 40 years.

In 1929, Dr. Omar Turney, created a map of the Salt River Valley showing the results of exhaustive surveys cataloging Hohokam Canal systems in the Salt River Valley. Dr. Turney’s astonishment and respect for the accomplishments of these ancient Hohokam engineers is evident in the text of the map “these were the original engineers, the true pioneers who built, used and abandoned the canal system when London and Paris were cluster of wild huts”.

Turney’s survey is the most definitive of the Salt River Canal system ever created. It was the product of observations made over the course of more than 40 years of study, and the map shows dozens of prehistoric canals on both sides of the Salt River in the vicinity of Phoenix, Tempe and Scottsdale. The map accompanied Turney’s multi-installment prehistoric irrigation in the 1929 Arizona Historical Review.

Turney’s map provides a record of the Hohokam Canal System which would be unmatched until extensive aerial surveys became available, and goes beyond this to supply irreplaceable archaeological evidence for the ruins of abandoned prehistoric temples and settlements in the area, subject to destruction at the hands of European settlers.

Turney laments: “40 years ago few [Hohokam Canals] had been destroyed. One by one we have seen them torn down, but so many remained that it seemed the whole story of the early race could be told many times over from those that remained. With keen resentment we heard an outsider come here and declare that all were gone. When this report was begun, it still seemed that plenty remained, we drove about to measure them up and with astonishment found that 31 edifices of the past are now of the past themselves: only two remain. As a report, this preliminary has become an obituary!”

Also, many of the Hohokam ruins found in the Salt River Valley are recorded with precision only on this map. In addition to specific temples in pueblos, the map notes the location of pictographs, pictoglyphs, and hieroglyphs throughout the region. A ceremonial grotto is marked on the Camelback Mountain, as does Phoenix’s famous “Hole in the Rock” landmark.

Confusingly, several of the names of ruins found on the map are drawn from Mormon scripture. Turney noted in his third installment of prehistoric irrigation that: “Casa de Nephi was so named in thanks to the leaders in the Mormon church for their long and untiring efforts to check and verify every detail of the Turney map in their part of the [east] valley. Names in this locality are taken from the book of Mormon.” Other such place names include Pueblo Moroni and Pueblo Lehi.

The personalizing feature appearing on the map is on the north bank of the Salt River is the “Park of Four Waters“. Turney chose this location – now part of the Pueblo Grande Museum – to be the final resting place of his ashes after his death.

Water Associations Co

  • Central Arizona Groundwater Replenishment District
  • Central Arizona Project
  • Water Asset Management, hedge fund
  • Greenstone, hedge fund
  • PICO Holdings, the public company that owns Vidler
  • National Climate Assessment
  • Arizona Land and Water Trust
  • Arizona Water Banking Authority- In 1996, the state created the Arizona Water Banking Authority to take that water and store it underground. But even the water bank didn’t have the space or the money to store it all.
  • Mohave County Water Authority- Maureen George, was an attorney who represented Mohave County until she retired.
  • Water Resources Research Center at the University of Arizona
  • Scottsdale’s Water Department
  • Bureau of Reclamation
  • Bonneville Environmental Foundation
  • Business for Water Stewardship

In Arizona, an investor can speculate on water can try their hand in a few ways. They can buy land with rights to water, either ground or surface. Or they can purchase what’s called “paper water”— tradable credits for water artificially stored underground. They can also buy water, store it, and create those credits themselves.

In 1997, Vidler decided to build a storage facility on the land it purchased from Borowsky and his partners. The structure would transfer water to an aquifer, either by letting it sink through layers of silt, sand, clay, and gravel or by using a new technology, vadose zone wells, to inject it. Timian-Palmer estimated the company spent $15 million just to build the recharge project. “It was, by far, the state of the art in those days,” said Small, the groundwater hydrologist who designed the pilot site.

By October 1998, the Vidler Recharge Facility pilot project was up and running. It was likely “the first privately-owned water storage facility for the Colorado River system,” parent company PICO Holdings reported in its 10-K filing to the Securities and Exchange Commission in 2000. Once expanded to a full-scale facility, it would take in 100,000 acre-feet of water per year and could cumulatively store more than 1 million acre-feet, the company predicted.

“We anticipate that in the future, a significant amount of Vidler’s revenues and asset value may be derived from [this] single asset,” it said. “Potential users include local governments in Arizona, the Las Vegas metropolitan area, California, and the Bureau of Reclamation.” Vidler would charge users a fee depending on the amount of water stored, then more fees for recharging and recovering the water.

In those days, Arizona “pretty much encouraged people to come in and recharge water,” said Timian-Palmer. Excess Colorado River water was “competitively priced” if it went to underground storage.

Vidler started purchasing that water — at first about 1,000, maybe 2,000 acre-feet a year — in 1998 and storing it underground. By 2001, it had expanded its facility. That year, it was in the midst of negotiating with the Arizona Water Banking Authority “to begin recharging water and generating cash flow from the facility.”

That income never materialized. Although they signed an agreement, “water was never stored by the bank at Vidler,” said Virginia O’Connell, the water bank’s current manager, because Vidler’s was more expensive than other facilities.

In 2010, Vidler purchased a company with water credits in Phoenix. In 2013, it made $6.3 million selling about 1,000 acres of land and groundwater rights in the Harquahala Valley to Scottsdale for two of the city’s golf courses. But the company continued to lose money, operating at losses of more than $12.5 million in 2014 and nearly $4 million in 2015. In 2017, Vidler sold the Arizona Water Banking Authority about 50,000 acre-feet of its Phoenix credits, and the same amount to the Central Arizona Groundwater Replenishment District, for a total of $25.9 million.

The District, created by the Legislature in 1993, has been key in creating demand for credits in Arizona. In the areas around Prescott, Tucson, and Phoenix, state law requires developers to put as much water back into the ground as they take out, all in roughly the same geographic area. The District helps developers meet that requirement, but it doesn’t have to buy actual water and put it in the ground. Instead, it can buy credits from others who’ve already done so. Critics level that the District allowed development in areas that had no renewable water supply.

“What we’re talking about is transfers of water from the place where there is water to a place where there isn’t water,” said Sarah Porter, director of the Kyl Center for Water Policy at Arizona State University. “I think that there’s more speculation in water as a result of the creation of [the District].”

Vidler has stashed away more than 250,000 acre-feet of water in its recharge facility in the Harquahala Valley — a quarter of its capacity of 1 million acre-feet. The final year Vidler bought excess Colorado River water was 2010, when it put 50,000 acre-feet into the aquifer. After that, the supply dried up.

Last fall, the District hadn’t been interested in Vidler or Water Asset Management’s water because of the pending deal with the Gila River Indian Community, Grignano said. The District ultimately inked a $97.5 million deal to buy enough water from the Gila River Indian Community to fulfill “a substantial portion” of the water it would need over the next 25 years.

Arizona Water Canals

The Ancient Desert Dwellers

The ancestors of present-day Salt River Pima-Maricopa Indian and Gila River Indian communities were farmers who lived in central and southern Arizona for about 1,400 years before European and American explorers came to the region. The intricate canal system that they built spanned nearly 500 miles and may have served as many as 50,000 people at one time.

Archaeologists don’t know exactly why the ancient farmers stopped maintaining their canals around 1450 A.D. It is thought that environmental changes, drought, violent floods or eroding rivers may have made it difficult to farm the Salt River Valley.

The ancient desert dwellers set the groundwork for the water canal system, which follows many of the same paths today.

The Pioneers

In the 1860s, a central Arizona gold rush brought an influx of people to the Salt River Valley. In December 1867, a group of 17 of these new arrivals formed the Swilling Irrigation and Canal Company. This group planned to take water from the Salt River by canal so they could grow crops to sell to miners at Wickenburg and the U.S. Cavalry stationed at Fort McDowell. The waterway became known as the Swilling Ditch, later the Town Ditch or the Salt River Valley Canal.

By March 1868, farmers under the Swilling Irrigation and Canal Company had harvested their first crops on land near the present-day Arizona State Hospital. During that same month, a government survey party came to the Valley and noted that a small community calling itself “Phoenix” had appeared on the scene.

Settlers Form a Water Association

A severe drought in the late 1890s created a water shortage in the Salt River Valley. At one point, river flow dwindled to 25 cubic feet (about 187 gallons) per second. Thousands of acres of agricultural land went out of production and hundreds of people moved away.

For those who remained, the obvious solution was to build a water storage dam to capture spring runoff. In 1902, the National Reclamation Act was passed into law. The Act provided for government loans to “reclaim” arid lands in the Western United States with irrigation projects. In 1903, the Valley settlers formed the Salt River Valley Water Users’ Association. The Association pledged more than 200,000 acres of land as collateral in order to secure a government loan to build a water storage and delivery system.

While the major effort in Arizona was the Theodore Roosevelt Dam, government engineers also saw an opportunity to improve existing Valley canals and create efficiencies by unifying the canal system. One by one, the government purchased the Valley’s private canals.

In 1917, operation of the canal system was turned over to the Salt River Valley Water Users’ Association, which still operates the canals for the federal government today.

Salt River – Rio Salado

In the late 1800’s there were 9 canals siphoning water off the Salt River as it flowed south and then west across the wide desert floor. Most followed the tracks of canals built hundreds of years earlier by the Hohokam Indians. Three canals, the Grand, Salt River and Maricopa, drew north of the westward flowing river. Five canals drew from the south. The newest canal, the Arizona, drew further north, feeding vast acreage across the northwest.

Arizona’s Major Water Canals

Over the past 100 years, nine major water canals have emerged across the greater Salt River Valley.

1. Arizona Canal (1883)

Measuring more than 38 miles long, the Arizona Canal is the longest canal in Arizona. It’s the main canal that transports water to all others on the north side of the Salt River.

The canal was the work of the Arizona Canal Company, which was formed in December 1882. Construction began in May 1883 and was completed in 1885. Water began flowing the next year. The Arizona Canal helped bring water to the north and across to the West Valley, allowing for development of these areas.

The original heading was the old Arizona Dam, located on the Salt River about a mile below the mouth of the Verde River. Unfortunately, that dam was destroyed in a spring flood in 1885. A stronger Arizona Dam was rebuilt by December 1886. Though the second Arizona Dam was the only pioneer diversion dam that survived the big flood of February 1891, it was damaged by a flood in 1905 during the construction of Roosevelt Dam. In an effort to unify the Valley’s water delivery system, the Secretary of Interior agreed to purchase the canal in 1906. The government assumed operations of the Arizona Canal in May of 1907.

2. Grand Canal (1878)

The Grand Canal is the oldest remaining pioneer canal on the north side of the Salt River. It was planned in 1877 and constructed in 1878 by the Grand Canal Company. The original heading of the Grand Canal was plagued by washouts, which would interrupt its water supply for months at a time, so the Old Crosscut Canal was built to provide a more reliable water supply from the Arizona Dam and the Arizona Canal. Today, the Grand Canal receives water from the Arizona Canal by way of the New Crosscut Canal.

The Grand Canal provided a better route for service of central Phoenix than the Salt River Valley Canal, which led to the abandonment of the Salt River Valley Canal in 1925.

The federal government purchased the Grand Canal for $25,731 in June 1906. At that time, the canal served about 17,000 acres.

3. The Crosscut Canals: Old and new (1889 and 1912)

The Old Crosscut Canal was built near 48th Street by the Arizona Improvement Company to unify the entire northside canal system by connecting the Arizona and Grand canals. After the New Crosscut was built near 64th Street, the Old Crosscut was used only for drainage, emergency flood relief or during repairs to the New Crosscut.

The New Crosscut (or Arizona Crosscut) was financed and built by the Water Users’ Association in 1912 and turned over to the U.S. Bureau of Reclamation upon completion in 1913. This canal leaves the Arizona Canal near 64th Street and crosses Papago Park before it drops 116 feet through penstocks (pipes) to the Crosscut Hydroelectric Generating Station south of Washington Street. Then it enters the Grand Canal. The completion of the New Crosscut Canal and hydro plant made electric power generation possible on the canals while still allowing for the efficient delivery of irrigation water.

When it was built, the Crosscut Hydro Plant was the second-largest generating station, the Roosevelt Dam was the largest. The New Crosscut Canal’s bank is where the Valley’s first concrete canal-side bicycle path was built in 1975.

4. South Canal (1908)

The South Canal serves the very important purpose of taking water from the Salt River at the Granite Reef Diversion Dam to all of the other canals on the south side of the Salt River.

The South Canal was built by the federal government between 1907 and 1909 to unify the entire southside canal system. Originally, the South Canal was only 2 miles long before splitting into the Consolidated and Eastern canals. However, the Consolidated Canal, nearer to the river, was repeatedly damaged by floods. In 1920, the Eastern Canal was widened to become the main canal for the southside system. The entire 10-mile stretch to the division gates where the Consolidated and Tempe canals separate is now called the South Canal. The first South Canal hydro plant, built in 1912 at the split of the Consolidated and Eastern canals, was moved to its present site in 1924 to take advantage of a drop in the canal. From 1927 to 1929, the South Canal and parts of the Eastern and Consolidated canals were lined with concrete. The concrete liner saved water and increased the supply to the Roosevelt Water Conservation District (RWCD).

The three most significant features along the canal are the Val Vista Water Treatment Plant, the Hennessy Wasteway and the South Consolidated Hydroelectric Plant.

The Hennessy Wasteway is used to discharge excess rainwater from the Salt River. It is also used as the turnout to the Granite Reef Underground Storage Project (GRUSP). Located on a 350-acre site southwest of Granite Reef Diversion Dam, GRUSP stores water from the Salt River and water delivered through the Central Arizona Project. Water is contained at the site and allowed to sink into the ground, recharging the underground aquifer and bolstering groundwater resources.

Another feature on the South Canal is the RWCD pumping plant, which takes water from the South Canal into the RWCD Canal. West of Lindsay Road, the South Canal splits and becomes the Eastern Canal to the southeast and the Consolidated Canal to the southwest.

5. Eastern Canal (1909)

The Eastern Canal is a branch of the South Canal that originates west of Lindsay Road near McDowell Road in northeast Mesa. Built by the federal government in 1909, the Eastern Canal replaced the old Highland Canal, which was one-quarter mile to the west. The Highland Canal had been completed in 1888.

Concerns about water rights, coupled with droughts in the late 1890s and early 1900s, helped motivate landowners served by the Highland Canal to pledge their property as collateral to form the Association. Today, the Eastern Canal is the site of the Town of Gilbert’s water filtration plant.

6. Consolidated Canal (1891)

Although it is the largest canal in Mesa (roughly 18 miles long), the Consolidated Canal wasn’t built to serve any of the land within the present city limits.

Started in 1891, the canal was masterminded by Dr. A.J. Chandler and his Consolidated Canal Company. Chandler’s desire was to bring water to the area that now bears his name.

Because the canal was built during one of the driest periods in the Salt River’s history, its owners faced supply problems. Lands with older water rights had first claim on the meager water supply in the Salt River, and the occasional surpluses that occurred were too small to cultivate new land.

Nevertheless, Dr. Chandler was imaginative. Recognizing the problems that owners of the Mesa and Tempe canal companies were having with brush diversion dams, he began bargaining.

In exchange for water to be saved by his proposals, Dr. Chandler offered to build a new diversion dam made of huge boulders. The south end of the dam tied into granite masonry abutments and wing walls – the head of the new canal.

Using a huge dredge, Dr. Chandler built a canal up to 26 feet deep. Two miles south of the heading, the canal emptied some of its water into the old Mesa Canal. The Consolidated Canal then divided into two branches as it does today. The Consolidated Canal also delivers to the Chandler Water Filtration Plant, which is located south of Pecos Road.

The branch heading west was called the Crosscut Canal, and for about two miles, it followed what is now Brown Road to the edge of a small mesa near the Tempe Canal. This spot is where Chandler built the Chandler Falls Power Plant that provided electricity to Mesa and Tempe.

By carrying Tempe Canal water through the Consolidated Canal, instead of through a sandy riverbed, canal owners were able to prevent a considerable amount of water loss from seepage. This “new” water became part of the Consolidated Canal, which followed the old Mesa Canal to Baseline Road and on to Chandler.

Recognizing the water savings that the Consolidated Canal made possible, the federal government later sought to acquire the canal as part of a unified water distribution system for the Association. Government engineers saw that all canals south of the Salt River could be interconnected by building a new 6-mile length of canal from Granite Reef Diversion Dam to the Consolidated Canal.

7. Tempe Canal (1871)

The Tempe Canal is the oldest continuously used canal in Arizona. Construction of the Tempe Canal was undertaken by the Tempe Irrigating Canal Company, which had originally been incorporated in 1870 as the Hardy Irrigating Canal Company, though the name was changed the following year. The first Tempe Canal headed in the Salt River near what is now Mesa Drive in Mesa. It flowed along 8th Street to downtown Tempe and on to the west where it also supplied the San Francisco Canal. A branch served the Broadway-Alameda area south of downtown. In the 1880s, further branches were dug south along Price Road (a portion now known as the Tempe Canal), west along Guadalupe Road and around the base of South Mountain to south Phoenix.

Charles Trumbull Hayden, the “Father of Tempe,” was among the early homesteaders served by the canal. He first came to the Valley in 1870 and saw the need for a store, ferry service and flour mill at the river near what is now Mill Avenue. Hayden began building the mill in 1872. It began operation two years later, using power generated by water from the Tempe Canal by way of an extension ditch. Some of the earliest pioneers in this area were the Sotelo and Gonzales families, who both worked on the construction of an early branch of the Tempe Canal, the McKinney-Kirkland Ditch, and farmed in the area as well.

The increase in irrigation brought about by Roosevelt Dam raised the water table all over the Valley. Because of geological formations, land in Tempe was at high risk for waterlogging. The Association had the resources — including the electric power — to drain these lands with pumps, and its commitment to make Tempe a priority for drainage convinced the Tempe farmers to join the Association.

8. Western Canal (1912-1913)

Work on the Western Canal was started in 1911 and the government dug the canal from Price Road to 48th Street before was suspended in 1912 due to funding problems. The government also built three feeder laterals to bring a water supply from the Consolidated Canal and a siphon to carry the Western Canal under the Tempe Canal. Farmers in the south Phoenix area formed the Western Canal Construction Company in 1912 to fund and build the canal from 48th Street to 19th Avenue. When completed, this section was deeded to the U.S. Bureau of Reclamation and the farms of south Phoenix finally had an assured supply of water.

Some farmers in south Tempe and south Phoenix had lands on the lower slopes of South Mountain, which was above the Western Canal. In 1912, these farmers formed the Highline Canal Construction Company and sold stock. They raised $100,000 to build a pumping plant, pipeline and canal. The pumping plant took water from a bay in the Western Canal and pumped it 40 feet uphill through a 1-mile pipe, where it emptied into the Highline Lateral for distribution.

From the Tempe Canal, the Western Canal heads west then turns and curves around to the northwest along the foothills of South Mountain. Roughly at the Maricopa Freeway, the canal continues its western jaunt, then dips to the southwest near 7th Avenue.

Drivers traveling along Baseline Road between the freeway and Central Avenue can see the Western Canal just north of the road. The Western Canal now has the Highline Pumping Plant, located east of Kyrene Road, to lift water to the Highline Canal.

9. The Central Arizona Project (1968)

As the state of Arizona grew, water providers understood that additional water supplies would be necessary to support Arizona’s cities, agriculture, business and industry, and so the Central Arizona Project (CAP), to life. The CAP’s canal system transports water across the desert from the Colorado River, carrying it to the state’s central valley where it adds to the region’s supply.

Lateral Canals

Arizona’s irrigation system includes hundreds of smaller waterways that connect to the main canals. These ditches, called laterals, take water from the large canals to delivery points in irrigated areas. Of the 1,074 miles of drains and laterals, over 85% have been piped to help reduce water loss — and more are lined or piped each year.

Water is routed into and through these laterals by a series of turnout gates. Residential irrigation customers take their water entitlement at regularly scheduled intervals throughout the year by opening valves that release water onto their property for specific time periods.

Most laterals north of the Salt River in urban areas are underground. Many of the laterals that take water from canals in agricultural areas south of the river are open ditches.

Hohokam Canals

From A.D. 600 to 1450, the prehistoric Hohokam constructed one of the largest and most sophisticated irrigation networks ever created using preindustrial technology. By A.D. 1200, hundreds of miles of these waterways created green paths winding out from the Salt and Gila Rivers, dotted with large platform mounds. The remains of the ancient canals, lying beneath the streets of metropolitan Phoenix, are currently receiving greater attention from local archaeologists. We are only now beginning to understand the engineering, growth, and operation of the Hohokam irrigation systems.

Early Records of the Prehistoric Canals when the first explorers, trappers, and farmers entered the Salt River Valley, they were quick to note the impressive ruins left by the Hohokam. Villages containing platform mounds, elliptical ballcourts and trash mounds covered with broken ceramic pots and other artifacts existed throughout the Salt River Valley.

Stretching out from the river was a vast system of abandoned Hohokam canals that ran from site to site across the valley floor. In the mid-1800s, the testimony of these ancient canals to intensive prehistoric irrigation, along with the success of the contemporary Pima Indian farmers, led Jack Swilling, John Y.T. Smith and the early Mormon pioneers of the Lehi settlement to begin the process of building a new community founded on irrigation agriculture.

In 1930 an aerial survey, made through the cooperation of the United States Army and the Smithsonian Institution, revealed nearly 125 miles of ancient canals in the Salt River Valley and about half that number in the Gila Valley. Many of the canals measured 30 feet, or more, from crown to crown, and reached depths of over 10 feet. Some of these canals may be traced over 10 miles from their intakes. In the Salt River Valley the total canal mileage consists of several independent units, each with its own intake which probably was constructed of rock and brush. Erosion of the riverbanks since the first Mormon farmers arrived to the valley has widened the channel to over a mile in many places and destroyed original intakes and portions of canals running adjacent to the original banks, which, according to early observers, were steep and well protected with vegetation. (Turney, O.A. Prehistoric Irrigation in Arizona. State Historian’s Office. Phoenix, 1929). The river seems to have been deep and narrow.

The ancient canals served as a model for modern irrigation engineers, with the earliest historic canals being formed largely by cleaning out the Hohokam canals. The canals were useful at times, being employed as wagon roads. In contrast, canals created unwanted channels through areas being developed by modern farmers. When a farmer purchased land, the area impacted by a prehistoric canal was often calculated and subtracted from the purchase to offset the costs incurred by filling it.

As modern farmers began to fill in the traces of the prehistoric canals, several prominent citizens became interested in these prehistoric monuments. They prepared maps showing the locations of canals, villages and mounds that form the basis of Hohokam scholarship today. James Goodwin, a local farmer, produced a map of the canals on the south side of the Salt River in what is now Tempe, Mesa and Chandler. Herbert Patrick, a professional cartographer and surveyor, mapped canals on the north side of the Salt River.

In 1922, Omar Turney, the City Engineer for the City of Phoenix, used these early maps combined with his own knowledge of local prehistory to publish the first comprehensive map of the prehistoric ruins and canals of the Salt River Valley. The most extensive records were made by Frank Midvale, an archaeologist who devoted his life to recording the traces of the Hohokam as the remains of their culture were destroyed by the rapid expansion of modern agriculture and urban growth.

Little is known about these people who established the first small hamlets along the terraces above the Salt River. They probably relied on floodwater farming techniques, planting in the wet soil in areas that had been inundated when spring runoff swelled the rivers beyond their banks. Perhaps as early as A.D. 50, these early inhabitants introduced a new technology, canal irrigation. This technology would eventually give form to the unique prehistoric culture of southern Arizona known as the Hohokam.

Canal irrigation was previously employed by peoples living along rivers and small drainages in Mexico, although their canal systems never attained the size and sophistication of the Hohokam canal systems. The earliest Hohokam irrigation systems may have been small canals located close to the river. In this location, the early canals would have been particularly susceptible to destruction by flooding.

Sometime between A.D. 600 and 700, Hohokam irrigation engineers designed the first large canals, capable of transporting large quantities of water onto the upper, or second, terrace of the Salt River. By the early Colonial period (A.D. 700 to 900), large integrated canal systems were established on both the north and south sides of the river. These canals were often monumental in their size and scope. Many of the canals were over 12 miles in length, with the largest recorded Hohokam canal extending for 20 miles. Two large prehistoric canals are still preserved in Park of the Four Waters, located in the southern portion of the Pueblo Grande Museum and Archeological Park. The canals measure 26 and 18 meters in width and approximately 6.1 meters in depth. Canal System 2, the large system that heads on the Salt River at Pueblo Grande, was probably capable of irrigating over 10,000 acres of land.

The Hohokam engineers were keenly aware of the local topography, the dips and slopes, drainages and soils. They developed a sophisticated knowledge of the flow of water through channels and developed a series of techniques for delivering water to the surface of the fields. Each technique was appropriate for a specific topographic setting such as steep slopes and flat river terraces.

The canal systems were designed with respect to the needs and characteristics of the environment. The canal systems contained a series of physical elements. Where the canal met the river, it is likely that a weir would be constructed. A weir is a dam that reaches into, but does not completely cross, the river. It raises the level of the water in the river and directs it into the canal. Inside the canal, a headgate (a large water control gate), was probably constructed to regulate the amount of water entering the canal.

The main canals transported the water away from the river toward the fields. Research has shown that the main canals are very large at their junction with the river but reduce in size as they progress toward their terminus. As the amount of water traveling through the canal decreases through discharge onto fields, evaporation and seepage, the size of the channel carrying the water is reduced. By reducing the channel, the velocity of the water remained relatively constant and between two critical thresholds: if the water traveled too fast, it eroded the sides of the canal; if the water slowed down, particles of soil would settle out of the water, causing the canal to quickly “silt up,” and require increased maintenance.

Distribution canals took water from the main canal system and transported it to the fields. They were also used to manipulate the relationship between the water level in the canal and the ground surface. Several types of water control features were used to operate distribution systems. Diversion gates have been found at the junctions of main and distribution canals to regulate water flow. Tapons or water control gates were often placed inside the main and distribution canals. When closed, the tapon would cause the water to back up and rise in elevation creating a “head of water.” Through the use of water control features, the Hohokam were able to create a highly sophisticated irrigation system.

Canal Construction
Building the Hohokam canals required a substantial investment of human labor. The soil was removed by hand, probably using large wedge-shaped pieces of stone called “stone hoes,” and wooden digging sticks to loosen the soil. The soil could then be removed from the canal using large baskets. Variations on the simple “leveling frame,” used in many preindustrial agrarian societies, could have been employed to establish canal gradients.

Recent reconstructions of prehistoric canals suggests that approximately 800,000 cubic meters of soil may have been removed for the construction of the main canals in Canal System 2 during both the Colonial and Classic periods, and in excess of 400,000 cubic meters during the Sedentary period (A.D. 900-1100).

The amount of labor required to construct the canal system was partially dependent on the volume of water flowing in the Salt River. The Hohokam experienced frequent flooding on the river. The flood waters often damaged or destroyed the canals, which were then redesigned and rebuilt.

It is difficult to estimate the actual time and effort required for the construction of the main canals. Many factors, including the amount of soil a worker can remove in a day, the number of hours worked in a day, the number of individuals working, and the number of continuous days over which the work is done, all affect estimates of time and labor expended. Given the ability of a single worker to move 3 cubic meters of soil per day, the construction of many canals would require in excess of 25,000 person days. This data suggests that the construction of Hohokam canals would have taken several decades to complete.

Sociopolitical Organization of Irrigation Societies
The construction, maintenance and operation of the canal systems would have required a substantial and well-organized effort. Individuals from all of the villages along a main canal would undoubtedly contribute to the initial construction and to the regular maintenance of the canal, weir and headgates. Each year, the amount of water allocated to each farmer was established. Perpetual conflicts over water arise between individual farmers and villages in irrigation societies even today. Thus, a strong leadership must have been necessary to quickly resolve conflicts which can threaten the cooperative ventures required for the continued operation of the large canal systems.

It is likely that the Hohokam canal systems were united into “irrigation communities,” sociopolitical units characterized by a hierarchy with distinct leadership roles. Each irrigation community would have its own leadership to organize labor for main canal construction, maintenance of the canals, headgates and weirs, the establishment of water allocations and scheduling, and to resolve local conflicts. Smaller, more local groups of farmers could organize for the construction and maintenance of branch canals and distribution canals.

The Role of Platform Mounds
Researchers have hypothesized that Hohokam platform mounds were tied to the organization and operation of the canal systems. Large administrative sites, containing one or more platform mounds, occur at the heads of the major canal systems. From this location, these sites controlled the flow of water in the main canals and better organized the necessary labor of annual repairs to the weirs and head gates. Other platform mounds are placed along the canals at regular, three-mile intervals and may represent secondary centers that controlled smaller territories along the canal system.

Destruction of the Hohokam Canals

In less than 50 years, the construction of a modern irrigation network and the building of Phoenix, Tempe, Mesa and other Anglo towns of the Salt River Valley erased most of the surface indications of the prehistoric Hohokam irrigation system. Today, we are left with only a fragmentary record composed of old maps, aerial photographs, and the usually truncated remains of canals in the earth.

Summary
The Hohokam engineered large and sophisticated canal systems, creating a productive agricultural society that spanned many centuries. Their achievements in irrigation engineering are among the most impressive and most enduring ever constructed using preindustrial technology. It is likely that a complex social and political structure was developed to construct and manage the canal system. Sites with platform mounds appear to have served as possible ceremonial and/or administrative centers. In any event, sites such as Pueblo Grande played crucial roles in the construction, organization and operation of the Hohokam canal systems.

Suggested Reading
Ackerly, Neal W., Jerry B. Howard and Randall H. McGuire
1987  La Ciudad Canals: A Study ofHohokam Irrigation Systems at the Community Level. Arizona State University Anthropological Field Studies, No. 17. Tempe.

Breternitz, Cory D. (editor)
1991  Prehistoric Irrigation in Arizona: Symposium 1988. Soil Systems Publications in Archaeology No. 17, Phoenix.

Haury, Emil W.
1978  The Hohokam: Desert Farmers and Craftsmen, The University of Arizona Press, Tucson.

Howard, Jerry B. and Gary Huckleberry
1991  The Operation and Evolution of an Irrigation System: The East Papago Canal Study. Soil Systems Publications in Archaeology No. 18, Phoenix.

Masse, Bruce
1981  Prehistoric Irrigation Systems in the Salt River Valley, Arizona. Science 214(23):408-415.

Midvale, Frank
1968  Prehistoric Irrigation in the Salt River Valley, Arizona. The Kiva 34:28-32.

Turney, Omar
1929  Prehistoric Irrigation in Arizona. Arizona Historical Review 2(5). Phoenix.

Patrick, Herbert- A professional cartographer.

Haury, Emil W.
1976 The Hohokam Snaketown. Univ. of Arizona.
1967 The Hohokam, the First Masters of the American Desert. Nat’l Geographic.

Graf, William

Nials, Fred

Rice, Glen

Henderson, Kathleen

Kisselburg, JoAnn

Swilling, Jack

Smith, John Y.T.

Goodwin, James- Local farmer who produced a map of the Hohokam canals.

Turney, Omar- City of Phoenix engineer in 1922.