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How to Water Your Garden With Flood Irrigation

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.

How to Water Your Garden With Flood Irrigation

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

How to Water Your Garden With Flood Irrigation

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

How to Water Your Garden With Flood Irrigation

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 With Flood Irrigation

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
How to Water Your Garden With Flood Irrigation

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.

How to Water Your Garden With Flood Irrigation


3. Fill the tank each time you have irrigation 

How to Water Your Garden With Flood 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. 
How to Water Your Garden With Flood Irrigation

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

How to Water Your Garden With Flood Irrigation

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.

How to Water Your Garden With Flood Irrigation

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

How to Water Your Garden With Flood Irrigation

 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.

How to Water Your Garden With Flood Irrigation

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.

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If this post about how to water your garden with flood irrigation was helpful, please share it:

Sources:

  1. https://blog.srpnet.com/managing-flood-irrigation/
  2. https://www.amwua.org/blog/why-are-we-still-using-flood-irrigation-in-the-desert

Resources:


Dory

Thursday 30th of May 2024

I am unable to use the flood irrigation system. It does sound interesting. Instead I use the grid system from Garden in Minutes. My question is how long should I be watering my 4X4X17 inch bed to adequately provide sufficient water for my plants. Thanks for your comments.

Angela Judd

Thursday 30th of May 2024

I love the Garden Grids. Everyone's soil and water pressure is different. Water long enough to penetrate to 10-12 inches. It may work best to break this up into a few segments so water has time to penetrate and doesn't run off. For example do 3 minutes, wait 15 minutes and then do 3 minutes more. Repeating until the soil is hydrated. Could take anywhere from 9-15 minutes (or more, or less!).

Amanda

Monday 15th of January 2024

Thank you!! This is so very helpful. I have two acres in Waddell that has flood irrigation. I’ve been trying to figure out a way to water the garden beds with the irrigation water. The plants will be so much happier.

Angela Judd

Monday 15th of January 2024

You're welcome. Glad it's helpful.

Dee

Saturday 13th of January 2024

Fascinating! I had no idea flood irrigation for homeowners even existed!