Questions and Answers Regarding the Watering Index and ET (EvapoTranspiration)

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1 Questions and Answers Regarding the Watering Index and ET (EvapoTranspiration) What is the Watering Index? The Watering Index is a scientifically based guide that was created to help people adjust watering schedules for landscape irrigation controllers (also known as "sprinkler timers"). The adjustment is by percentage. The Watering Index is a value which represents a recommended percentage. In much of the Northern Hemisphere, The Watering Index is normally 100 percent for much of July and August. As weather, or climatic conditions change over the course of the year, The Watering Index Value changes to reflect the landscape s changing need for water. As new Watering Index Values are published, your sprinkler timer programs should be adjusted accordingly to match the Watering Index Value. Who should use the Watering Index? Homeowners, gardeners and landscape maintenance professionals may easily use the Watering Index to make sure that the landscapes that they care for are getting the optimum amount of water based on weather conditions year round. Optimum means enough water to keep plants healthy and well maintained, and not an excessive amount which is expensive and wasteful. How is the Watering Index used? The Watering Index is used as a guide to help homeowners, gardeners, and landscape maintenance professionals make weather based decisions regarding the adjustment of automatic sprinkler timers. The Watering Index considers annual weather cycles and historical weather data, and provides guidance as to how your landscape s watering needs change with respect to historical and current weather data. The Watering Index is a percentage based on the maximum amount of water you should apply to your landscape. The maximum amount is typically the amount you would use in July or August, when temperatures are high, rainfall is scarce and days are long. But, for example, beginning in September, as days grow shorter and water remains in your soil longer, the amount of water required by your landscape is just a fraction or percentage of what was required in July and August. Think of it this way: during hot, dry weeks in July, you are watering at 100% of your landscape s maximum need. During April, when days are shorter and cooler, your landscape s water requirements are much less and so in April, the weather based Watering Index Value may be equivalent to just 50% which indicates that your landscape really only needs 50% of the amount of water it will require in July and August. 1 of 7 WaterDex TM is a Product of Rockrose Technology

2 Why is it important to adjust sprinkler timers weekly? Weather is variable, and our watering times should be too. You can save a considerable amount of water by adjusting your WaterDex to match the Watering Index. Although a new Watering Index Value is calculated and published daily, adjusting your WaterDex to the current Watering Index Value approximately once per week is sufficient to reduce water consumption while maintaining a healthy landscape. Reducing your water use will reduce your water bill and help save a very precious and limited resource. What is the basis for the Watering Index? The Watering Index is based on ET data (Evapo Transpiration) which quantifies your soil s water loss due to evaporation and transpiration by plants in terms of inches of water per day. ET is calculated from specialized weather stations that measure solar radiation, air temperature, relative humidity and wind velocity. An efficient watering schedule for your landscape should be designed to periodically replace the amount of water lost via ET. Watering less than this can lead to plant stress. Watering more than this can be excessive, expensive and wasteful. The Watering Index Value is simply the current ET for your area as a percentage of the highest average ET value for the previous 10 years. The concept behind the Watering Index was developed by Mr. John Wynn, currently with the State of California Department of Water Resources. Do I have to calculate the Watering Index Value? No. California residents may obtain the current Watering Index Value for their area at Anyone can register to have the Watering Index Value for their area e mailed or sent via text message to their mobile phones as a free service. This makes things Smart, Simple, and Convenient! Seattle area residents may obtain their Watering Index Value at Other Non California residents should contact their local water agency and enquire about how the water agency is making the local Watering Index Value available. Where does the ET data come from that is used to calculate the Watering Index Value? In California, both the historical and actual ET data is collected from The California Irrigation Management Information System (CIMIS), CIMIS is a program of the Office of Water Use Efficiency (OWUE), California Department of Water Resources (DWR) that manages a network of over 120 automated weather stations in the state of California. CIMIS was developed in 1982 by DWR and the University of California, Davis to assist irrigators in managing their water resources efficiently. Efficient 2 of 7 WaterDex TM is a Product of Rockrose Technology

3 use of water resources benefits Californians by saving water, energy, and money. The CIMIS weather stations are randomly distributed throughout the State of California. Please see to see which CIMIS station is used to calculate the Watering Index for your area. But CIMIS weather stations cover large areas. Wouldn t a weather station that is closer to my home reflect my landscape s weather conditions more accurately? Yes, but watering based on the Watering Index principal does consider local conditions. The watering run times (the minutes per electric valve or per station and the number of days of watering per week), which are set by you or your gardener, already reflect your particular climate. The Watering Index simply specifies the percentage of time your watering run times for each station should be set for depending on the time of year and annual weather cycle. Questions and Answers Regarding the WaterDex TM What is the WaterDex? For a fraction of the cost of a new smart sprinkler timer, no monthly service fees, and no radio signal broadcast requirements, WaterDex converts your existing sprinkler timer into a weather based sprinkler controller. Simply connect the WaterDex adapter to your existing sprinkler timer and place the WaterDex wireless remote control (shown below) anywhere inside of your home or garage within 150 feet of your sprinkler timer. The WaterDex remote control allows you to make adjustments to your sprinkler timer from anywhere in your home with the simple turn of a dial. The WaterDex is Smart, Simple, and Convenient. 3 of 7 WaterDex TM is a Product of Rockrose Technology

4 What are the benefits of using the WaterDex? Saves Money The WaterDex will save you money by reducing your outside water use. If you are like most people, you or your gardener re program your sprinkler timer just twice a year. While this may keep your lawn green, it is also a tremendous waste of money and water. The graph below shows the amount of water consumed when a typical twice per year timer re programming is performed ( ), vs. the amount of water consumed when watering based on the Watering Index ( ). The blue area in between the two lines represents the savings made available by using the Watering Index based WaterDex. It is important to point out just how closely the Watering Index Value tracks with ET ( ). This is not surprising, however, because the Watering Index Value is based on ET! Conserves Water The WaterDex s patent pending technology allows you to easily adjust watering duration throughout the year. This will not only help reduce excessive watering, water run off, and water damage to hardscaping and other structures, the WaterDex also gives you the personal satisfaction of knowing that you are doing your part to help save water. 4 of 7 WaterDex TM is a Product of Rockrose Technology

5 Weather Based Control WaterDex allows you to adjust your entire sprinkler system to match your local weather conditions from anywhere in your home and with the simple turn of a dial. Everyone knows that watering based on local weather conditions makes good sense because it allows you to keep your landscape healthy without wasting water. Using the WaterDex just makes it simple. Smart, Simple, and Convenient If you are like most homeowners, your sprinkler timer is installed where it is out of sight, and out of mind. While it may occur to you over the course of the year that you should re program your sprinkler timer, it s just not convenient, and re programming the timer is a hassle. By keeping the WaterDex wireless remote control somewhere convenient, you can adjust your sprinkler timer whenever you like with the simple turn of a dial. Mount your WaterDex remote control next to the garage door opener, stick it on the side of your refrigerator, or place it on a desk or counter top. Smart, Simple and Convenient! How do I use my WaterDex? Once the WaterDex is installed and regardless of the time of year, adjust your sprinkler timer to the settings you would normally use during the warmest, driest time of year. This will represent a Watering Index of 100% for your landscape. Next, obtain your area s Watering Index Value from or your local water agency. Finally, simply adjust the dial on your WaterDex remote control to match your area s Watering Index Value. Your WaterDex will now do the rest. The next time your sprinkler timer begins a watering cycle, the WaterDex will automatically adjust the watering time in each of your sprinkler system s zones to match the value on the WaterDex dial. For example, if your timer is set to run for 10 minutes in zone 1, and 12 minutes in zone 2, and the WaterDex is adjusted to 50%, the watering time in each zone will automatically be adjusted to 50%, or to 5 minutes in zone 1, and to 6 minutes in zone 2. This is accomplished by simply adjusting the WaterDex dial, and without any adjustment to your sprinkler timer program. You may never have to program your timer again! Do I have to re program my existing sprinkler timer? No Re Programming and that s the beauty of the WaterDex! Simply connect the WaterDex receiver to your sprinkler timer, and then place your WaterDex remote control anywhere in your home. No more having to go outside to re program your controller because the WaterDex s wireless remote brings the sprinkler controller into your home. Instead, simply adjust the WaterDex remote control dial to the desired Watering Index Value, and the WaterDex s patent pending technology automatically adjusts the watering duration in each zone of your sprinkler system to the Watering Index percentage value of your current program. 5 of 7 WaterDex TM is a Product of Rockrose Technology

6 What if my WaterDex is set at the Watering Index Value and my plants look stressed? Even though the Watering Index is scientifically based, the Watering Index Value is a helpful tool and not an absolute. The Watering Index coaches you regarding when watering adjustments should be made and how large those adjustments should be, however homeowners, gardeners and landscape professional still need to pay attention to the health of the landscape for which they are caring. If plants look stressed after setting your WaterDex to the Watering Index Value, increase the WaterDex percentage by 3% 5%. After making the adjustment, allow several days to see whether the stress disappears. If signs of stress remain, increase the percentage again. Make these periodic adjustments until the landscape appears healthy. There is a beneficial flip side to the notch adjustment technique described above, and made possible by WaterDex. If your WaterDex is set at the value of the Watering Index, and if you ve made no adjustments, and if the landscape looks healthy, the watering system may actually be applying more water than is necessary, meaning you are paying for more water than you need to. To check if this is the case, reverse the process described above. Reduce the percentage by 3% 5%, and observe your landscape for several days. Once you ve reduced the percentage to a point where the plants are beginning to show signs of stress, increase the WaterDex adjustment by 2% 3%. What if my sprinkler timer already has a percentage adjust, or water budget feature? If this is your case, simply think of your WaterDex as having taken over responsibility for the percentage adjust, or water budget feature, and placed it in a wireless remote control that you can place anywhere! No more having to go outside to the timer and reprogram or make adjustments. Mount your WaterDex remote control next to the garage door opener, stick it on the side of your refrigerator, or place it on a desk or counter top. When you install your WaterDex, simply adjust the percentage adjust, or water budget feature on your existing timer to 100%, and then use the WaterDex remote control the same way that you used the adjustment on your timer. What if my sprinkler timer doesn t have a percentage adjust, or water budget feature? WaterDex was developed for homeowners like you! WaterDex retrofits to existing timers with or without percentage adjust or water budget features, adds the convenience of a wireless remote control, and converts any timer into a weather based sprinkler system controller. Is there anything else I can do to improve my watering practices and reduce my outside water use? Yes, there is. In addition to having an optimized watering schedule and adjusting it weekly as the Watering Index would suggest, it is important to periodically turn on each 6 of 7 WaterDex TM is a Product of Rockrose Technology

7 irrigation valve to see that the valve and each sprinkler served by that valve are operating properly. Look for sprinklers that are not popping up properly, shrubbery or grass that is interfering with the watering pattern of a sprinkler, broken nozzles, clogged nozzles, sprinklers that do not pop up vertically, sprinklers that are spraying sidewalks and driveways, etc. If your water pressure is high, use pressure regulation devices to bring the sprinkler operating pressure down to the optimal pressure range specified by the manufacturer. Pressure that is too high causes the water exiting the sprinkler to turn to mist, which, can be blown away by even just a gentle breeze. Water in the early morning when the air is cool and still. Avoid watering between the hours of 10:00 am and 5:00 pm when much of your water will be lost to evaporation. For more information on landscape watering techniques which can reduce your outdoor water consumption, help you save money and protect the environment please visit and refer to the resources posted on our website. 7 of 7 WaterDex TM is a Product of Rockrose Technology