Using weather information to adjust your watering will save water, reduce water cost, reduce the need for fertilizer, and improve the heath of your plants. Weather based scheduling works by calculating how much water your plants need, then calculating how long to run your watering system. Since the need for water varies throughout the year you should regularly adjust your watering times.
We will concentrate on lawn watering systems since they account for a large part of your water consumption and they are the easiest to manage.
First, you must determine how your watering system performs. The application rate is the amount of water (in inches) applied per minute. By determining the application rate you can determine how long to run your sprinklers to apply the proper amount of water. We also need to know how uniform your watering system is. Uniformity is a measure of how evenly your system applies water. If your system were perfect then it would be 100% uniform. As uniformity decreases we must apply more water to insure that your plants remain healthy.
Second, you need to learn how to manage your watering system for best use of the water.
Finally, you can calculate how long to run your sprinklers.