How to Water Your Garden With Flood Irrigation

By: Angela Judd | January 8, 2024

If your property has access to flood irrigation, you know the benefits of deep watering for your landscape plants and trees. However, flooding your garden every 13 days may not be practical for watering raised beds and vegetable gardens. There is a way to water your garden using flood irrigation water that works well. This blog post explains how to install a flood irrigation system to effectively water your garden and raised beds.

How to Water Your Garden With Flood Irrigation

After the initial effort and investment, it is a low-cost solution for watering your garden. Not only does this method avoid the chemicals associated with treated water, but it is also much less expensive for the home gardener. Let’s dive into how to water your garden and yard using flood irrigation.

What is flood irrigation?

Flood irrigation is a system that captures and uses excess water from rainfall or snowmelt and provides a natural, chemical-free water source for your plants.

In the Phoenix Valley, most irrigation water originates from SRP’s 13,000-square-mile watershed. It channels melted snow and rain into the Verde and Salt rivers. SRP then routes the irrigation water to the customer through lakes, dams, canals, and laterals.¹

Homeowners in flood-irrigated areas have access to irrigation runs every 13 days with a dry-up period (for canal repairs) during the winter. The average cost for irrigation water is $6.80 per hour.

According to AMWUA, ”about 22,000 homeowners receive flood irrigation or about 5 percent of SRP lands.”²

My property does not have flood irrigation (I wish it did!), but my neighbor Larry Burnett‘s property does. I’m sharing the method he developed to use flood irrigation to water his garden.

Larry cleared the use of this method for his property with the Roosevelt Water Conservation District. Check with local authorities to ensure you comply with local laws or water regulations.

What are the benefits of flood-irrigated water?

Flood irrigation offers a cost-effective, untreated water source rich in nutrients that promotes robust root systems by storing water deeper in the soil, reducing the need for frequent watering and saline buildup. This method helps protect vegetation from drought and significantly reduces water evaporation compared to traditional sprinklers.¹

What are the challenges of using flood irrigation to water your garden?

Gardens often need watering more often than every 13 days.
You need more control over the amount of water than flooding with irrigated water offers.
Flood irrigation relies on gravity, so water can’t reach raised beds or other elevated areas.

How to water your garden and landscape plants with flood irrigation

1. Install a storage tank (or multiple tanks, depending on your water needs) and an internal pump

Select a tank (or tanks) based on your water needs. Check your water bill to get an idea of your outdoor landscape usage. Choose a location close to your sprinkler system if possible. Tanks should be opaque to prevent algae growth.

Install an internal pump (you’ll need to add electricity) to the tank. The pump will provide the water pressure to the drip lines.

Each tank needs:

Electrical line (to run the pump)
City water line
Sprinkler line
2-inch PVC hose connection
Overflow
Drain

2. Connect the tank to your sprinkler system and city water

Connect the tank and irrigation water to the existing sprinkler system. The tank then becomes an additional source, along with the city water for the sprinkler system.

Connect the tank to the incoming city water. This allows you to fill the tank with city water if needed. Install a switch on the line to your sprinkler system to enable switching between city water and irrigation water.

3. Fill the tank each time you have irrigation

When it’s your turn for irrigation, use an external pump to fill the tank.

Attach the pump’s hose to the irrigation source.
Run the 2-inch PVC discharge hose from the pump to your water storage tank.
Attach the hose to your tank.
Turn on the pump and fill up the tank.

A pump and 2-inch line allow Larry to fill his tank in 20-30 minutes during his regular irrigation runs.

Larry also suggests running your sprinklers and drips during the time you have irrigation while you are filling up your tank. This takes full advantage of water coming into your yard during your irrigation slot.

4. Use water from the tank to water your yard and garden

The internal pump provides the water pressure (especially as the tank empties) for the drip lines. It may take some experimentation to figure out the correct water pressure.

Ideally, your water pressure using the tank / or incoming city water is the same. If the pressure is different, your watering times will vary based on which water source you are using.

Adjust your valves as needed so you know how much water you use and how long it takes to water your garden and drip system.

5. Switch to city water as needed if the tank empties

If you run out of stored flood irrigation water, switch back to using city water.

Look at ways to lower your water usage or install an additional tank if you run out and use city water between each irrigation cycle.

Thank you to Larry Burnett for contributing to this post.

Larry Burnett is a retired Administrator from Banner Health and a Partner from KPMG. Larry has lived in Arizona since 1984 and gardened here extensively.

He is a Master Gardener through the University of Arizona and a mentor for Master Gardener students. His favorite time of the day is when he is outside in his greenhouse, garden, and flower beds.

Sources:

Resources:

Tank-N-Barrell 1750 gallon tank
Harbor Freight: Predator 6.5 hp, 212cc gasoline engine and 2-inch hose system
Galaxy Gardens: Rainwater and Tank installation company
DAB Tanks: Internal pump for the tank – There are various options and capabilities based on individual needs.