North Plains Groundwater

  Conservation District

How can I use the TXHPET Network to calculate when to water my turf grass?

It's a lot easier than you might think to calculate exactly when your grass needs to be watered.  Using the information being gathered by the TXHPET can save you money on your water bill and can also help conserve our precious groundwater resources.  Here's how to do it..........

Click on the link to the TXHPET station nearest to your location to get the ET information that will most closely approximate your conditions.  The EvapoTranspiration (ET) is calculated by taking into account weather factors, such as temperature and wind speed, as well as soil temperature and other factors. 

Once you reach that page of the website, you will see the name and location of the TXHPET Station in the upper left.  Beside the line that says "Station Information", you will see some blue links across the page.  Click on the one that says "grass" and you will see a little box similar to this:

This tells you what the evapotranspiration rate was for three common types of turf grasses: Fescue, Bermuda, and Buffalo.  You will also see that it gives you the amount of water lost, in inches, for yesterday, the last three days, and the last seven days. 

Most grasses need about 1 to 1 1/2 inches of water per week.  By adding the PET daily numbers for your type of turf, you can calculate when your lawn has lost this 1 to 1 1/2 inches of water.  You will also need to deduct any rainfall that you receive.  A handy worksheet to help you calculate the PET for your lawn and determine when to water can be downloaded here.   It is an Excel spreadsheet that will do the calculations for you if you use it on your computer, or you can print it out and enter the numbers by hand.

Remember that it's best to water your lawn thoroughly 1 to 2 inches at a time to encourage deep root growth.  Turf that is watered frequently and in smaller amounts will root more shallowly because the water is always available, and will be much more stressed during dry periods, while deeply rooted turf will be able to take advantage of deeper soil water and will tolerate drought stress much better.

If you're not sure how much water your sprinkler puts out in a given period of time, you can read how to gauge your sprinkler's output by clicking here.