Self Irrigation Audit

Our landscapes in Central Texas are very diverse and require supplemental watering to maintain their beauty. As you all know, our rainfall in Central Texas can be very sporadic. And, we all know plants love rainwater. If possible, I encourage you all to install rainwater catchments at your home. This can be as simple as buckets under your gutters’ downspouts or as elaborate as a rainwater harvesting system.

Regardless of the water used in your landscape, it is vital to be efficient in its use. As a TCEQ Licensed Irrigator, I encourage you to evaluate your irrigation system to ensure an efficient application of water. Here are simple, easy steps to auditing your irrigation system. Your eyes are the best tool.

Download an Irrigation Audit form (pdf) to help with your Home Self Irrigation Audit. 

Site and Component Inspection

Reducing the water applied to your landscape through maintaining your irrigation system is one component to reduce the unnecessary waste of water. The key to successful irrigation is understanding your system.

• Do you know if all of your sprinkler heads are functioning efficiently?
• How often and how long does your system run?
• Does your system run when it is raining?
• Does your irrigation encourage deep roots so plants are prepared for drought?

Common reasons for inefficient irrigation are broken sprinkler heads, misting heads, and overspray onto hardscapes. Take the time to watch your system run. These issues can easily be fixed. Your irrigation should not spray on sidewalks, driveways, fences or other hard structures. This can be fixed by adjusting the spray nozzles. Check for misting heads—this is a sign of too much water pressure. Check to make sure your sprinkler heads are not leaking water when turned off. This will reveal a broken seal. These easy steps will ensure your system is functioning properly.

Performance Testing and Irrigation Rates

You are ready to check the irrigation rate of your system. The most accurate determination of this rate is achieved by conducting a catch can test. Catch can tests measure the amount of water actually hitting the ground at various points in your landscape (see sidbar for more information). Calculate irrigation rates for each zone.

1. Turn on your irrigation system, one zone at a time, to locate and mark sprinkler heads.
2. Starting with zone one, position the catch cans in a grid-like pattern throughout the zone to achieve an accurate representation of sprinkler performance. Try not to place catch cans too close to sprinkler heads; this may alter your results.
3. Turn on zone one, allow water to fill the catch devices. Keep track of the minutes that the zone is allowed to operate (5-10 minutes is usually sufficient). There is no need to fill the catch cans completely. This is also a good time to check each sprinkler head to make sure they are functioning properly.
4. After a measurable amount of water has fallen, measure the depth of water (in inches) contained in each catch can. Record these values along with the minutes the zone was operating.
5. Repeat the steps for each zone on your system.
6. To calculate your irrigation rate in inches per hour, use this equation:

Irrigation rate= (average depth in catch can / test run time in minutes) x 60

Irrigation Scheduling and Run Time

Determining when to irrigate is based upon the depth of the plant’s roots and the type of soil. Together, root depth and soil type define the amount of water needed. For example, a six inch deep clay soil will hold more water than a six inch deep sandy soil. Thus, the number of irrigations per week will be less in the clay, though the amount of water the plant needs will remain the same. Root depth also influences the irrigation frequency. Shallow roots need water more often than deeper roots. A common way to determine root depth is to take a core sample of your turf grass. You may purchase a coring tool at your local hardware store. In general, the height of your turf grass is equal to the root depth: a 3” tall grass will have a 3” root depth.

Once it is determined how much water is needed for each irrigation event, the conversion to zone run time is simple. The following equation is used to determine zone run times (in minutes):

Run Time per Irrigation= (Targeted irrigation depth/ Zone irrigation rate) x 60

Now you can use your irrigation controller to schedule for efficient irrigation. Understanding the irrigation components, the precipitation rate and run time of your system is an important component to efficient watering.

Best Advice

As a Licensed Irrigator, I believe the best advice I can give homeowners is to visually inspect your system when it is running. You will easily save water by changing broken heads, adjusting water pressure so there is no misting, and realigning the spray as to not water on your hardscapes. These simple fixes can reduce the amount of water used by an average of 20%. Also, let your grass grow. Taller grass provides shade to the roots so they will be deep and healthy. So, take the time to get out in your yard and watch your irrigation system run. Many of you have spent a substantial amount on your landscape. Protect your landscape and save water.

If you have questions or concerns about your irrigation system, contact a local Licensed Irrigator to assist you in maintaining a beautiful, healthy landscape.

Guy Rials
Regulatory Compliance Specialist
TX Licensed Irrigator # 16801
Barton Springs/Edwards Aquifer Conservation District
(512) 282-8441 or bseacd@bseacd.org.