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How flood irrigation works

Flooded lawns are a familiar sight in certain parts of Phoenix. What isn’t as well known is just how far that water has traveled – from the mountains into the Valley through lakes, dams and canals. Learn how our system of irrigation works and where it all began.

On this page:

    It all starts with the watershed

    Most irrigation water originates from SRP's 13,000-square-mile watershed – an area of land that channels rain and melted snow into the Salt and Verde rivers.

    From there, SRP delivers irrigation water to customers through a system of lakes, dams, canals and laterals.

    Here’s an overview of how flood irrigation works and SRP’s role in delivering water to the Valley:

    Water soaks deep into the Valley’s roots

    During flood irrigation, yards are filled with 2–3 inches of water. This helps the water soak deeply into the soil, allowing trees and plants to grow strong, deep roots.

    This helps trees grow better and bigger, creating larger umbrellas of shade coverage. More shade means cooler temperatures within homes, which helps reduce the need for AC.

    SRP manages the system for delivery

    SRP delivers water throughout the Valley, to cities and irrigation customers, using a system of canals. Conservation has been at the heart of our water management strategy for more than a century.

    That’s why we partner with cities on water technology and pilot programs and have even set a goal to save 5 billion gallons of water – all so we can ensure a long-term, reliable water supply for the Valley.

    Learn more about SRP flood irrigation in Phoenix here.

    Zanjeros are the gatekeepers

    An SRP employee known as a zanjero (Spanish for “ditch rider,” pronounced sahn-hair'-oh) opens a gate to release water from the canal into a system of smaller waterways called laterals.

    Since the late 1800s, zanjeros have played a vital role in the control and flow of water in the Valley.

    They traveled hundreds of miles along canals (first by horse, then by truck) and opened head gates to release water from the major canals. Water flows into smaller canals and pipes where it will eventually irrigate lawns, reach our faucets and help grow our food.

    A history of transforming the desert

    The people of Arizona have long harnessed the power of water through irrigation to grow and strengthen the area. Explore the history of irrigation in our state, as well as its role in our future.

    Ancient origins

    The ancestors of the present-day Salt River Pima-Maricopa Indian and Gila River Indian communities were the Hohokam, 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 A.D. 1450. 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 SRP canal system, which follows many of the same paths today.

    A (gold) rush of 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. They 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

    Water resources were hard to come by for a booming population. Thanks to the National Reclamation Act of 1902, an opportunity to secure the Valley’s water future presented itself. Around that time, a diligent group of Valley ranchers and farmers formed the Salt River Valley Water Users’ Association (SRVWUA) in 1903. The group offered up their land as collateral for federal funds to build Roosevelt Dam, believing storing water for a more reliable supply was the key to the long-term growth and prosperity of the Valley.

    Serving the Valley today

    Today, SRP delivers more than 800,000 acre-feet of water to people in the Valley every year. What the Hohokam and our early settlers built has grown into a water management system made up of 131 miles of canals and 1,000 miles of laterals and ditches that bring irrigation water to Valley homes and businesses. Check out our irrigation service areas. Or, discover more SRP history.