Most lawns require a minimum of one inch of water per week. This can be accomplished by watering each section for one hour at a time. To ensure that your lawn is getting an inch per watering, place an empty tuna can in the lawn. Once the can is full you have reached one inch. It is best to water in this manner 2 -3 times a week if possible. Rain is the best supplier of water due to the natural occurrence of nitrogen, which is essential to the health of your lawn. It is hard to ensure that your lawn is getting enough water in some cases. Don’t be fooled by quick downpours. It may be a lot of water, but it is coming down too fast to soak in and most of rain is washed away. A hard, short storm may still need to be supplemented later in the week with a good watering. Water is lost from your lawn through a process called evapotranspiration. Evapotranspiration–usually referred to as “ET”– is the combined effect of water used by the plant and that which is lost to evaporation. ET is expressed in inches (or mm) of water per week. Your watering schedule should be set up to replace the water lost to ET. Check with your local university extension for ET rates in your area. Many areas publish ET rates in the daily press.
Greener, More Efficient Ways to Grow Your Lawn