The Basics

What is flood irrigation, and how does it work?

How the water gets from mountain snowmelt to your backyard — the valve, the schedule, and the Zanjero.

In Plain Terms

Flood irrigation = watering an area by flooding it on a monthly or bi-monthly basis.

Flood irrigation floods your entire property with 2–3 inches of water on a regular schedule and lets it soak deep into the soil. Instead of spraying the surface like a sprinkler, it saturates the ground — sending moisture down to where roots grow strong.

In most of the Greater Phoenix Valley, the water is delivered by SRP (there are other companies but SRP is the largest) through a system of canals originally dug by indigenous people between 300–1500 CE and expanded by later settlers in the 1800–1900s.

It arrives by gravity: when it is your turn, you open a valve and the water flows onto your land, filling it behind low dirt berms until it soaks in over a few hours.

It is one of the oldest irrigation methods in Arizona, and for growing trees it is still one of the best. It is also astonishingly affordable — typically $75 to $200 per year for the average household.

Actual costs vary by lot size, irrigation district and provider, delivery schedule, and usage. Provided for informational purposes only and not a guarantee of actual charges.

Flood irrigation delivery day flooding an Arizona backyard 2 to 3 inches deep
From Snowmelt to Backyard

The journey of the water.

The system serving the Valley moves water hundreds of miles by gravity — a feat of century-old engineering that still runs today.

Step 1

Mountain Snowmelt

Water begins as snow in Arizona's high country, melting into the Salt and Verde Rivers — not the Colorado River.

Step 2

SRP Reservoirs

The rivers fill a chain of SRP-managed reservoirs, which store the water and release it into 131 miles of main canals and roughly 1,000 miles of laterals.

Step 3

The Zanjero Opens the Gate

On your delivery day, an SRP Zanjero opens the gate at the top of your neighborhood's system and water flows by gravity toward your street.

Step 4

You Flood the Yard

You open your valve, the water fills your land 2–3 inches deep behind the berms, and it soaks in within a few hours — feeding roots for weeks.

Delivery Schedule

When does the water arrive?

Summer

Every ~2 weeks

April through September, water arrives roughly every 14 days, delivered around the clock — including holidays.

Winter

Every ~4 weeks

October through March, deliveries slow to about every 28 days, matching the reduced needs of dormant and semi-dormant trees.

Annual Dry-Up

~6 weeks in winter

Canals close for maintenance once a year, usually January–February — aligning almost perfectly with tree dormancy in Zone 9b.

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Frequently Asked Questions

How does flood irrigation work?

Water begins as snowmelt in Arizona's mountains, feeds the Salt and Verde Rivers, and is stored in SRP reservoirs. On your delivery day, an SRP employee called a Zanjero opens a gate at the top of your neighborhood's system. The water flows by gravity through ditches and pipes to your property, where you open your valve and flood the yard 2–3 inches deep. It soaks in within a few hours, leaving deep moisture that tree roots use for weeks.
Most flood irrigation in the Greater Phoenix area, including SRP-served properties, draws from the Salt and Verde River watersheds — not the Colorado River. That makes it more resilient to Colorado River shortage declarations, which primarily affect CAP water supplies. No desert water source is immune to long-term climate pressures, but SRP flood irrigation water rights are among the most senior and secure in the state.
In summer (roughly April through September), neighborhoods typically receive water about every two weeks. In winter (October through March), deliveries slow to about every four weeks, matching the reduced needs of dormant trees. There is also an annual dry-up period of about six weeks in winter when canals close for maintenance — which happens to align with tree dormancy.
A Zanjero (pronounced sahn-hair'-oh, Spanish for 'ditch-rider') is an SRP field employee who controls and measures irrigation flows within the SRP water distribution system. On your delivery day, the Zanjero opens the gate that releases water into your neighborhood's private irrigation system.
Keep Reading

Related flood irrigation guides.

Budget

How Much Does It Cost?

Depends on the district and lot size, but it's almost always cheaper than sprinklers.

Read the guide →
Protect Your Investment

Water Rights in Arizona

What appurtenant water rights mean and exactly what to verify before you buy.

Read the guide →
My Honest Take

Is It Wasteful?

The environmental tradeoffs — groundwater recharge, shade canopy, and growing food locally.

Read the guide →
Want the Full Picture?

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Everything you need to evaluate a flood irrigated property like a specialist — water rights, delivery schedules, infrastructure inspections, and growing potential. It's free.

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