 2850 Burton Drive - Cambria, CA. 93428 Phone:(805) 927-6240 - Fax:(805) 927-6242 Celebrating 130 Years of Service to Cambria 1877-2007! |
The Watering Index
If you have a recent model irrigation controller with a watering budget
or "percentage" adjustment, you can use the Cambria Watering Index
to easily make regular adjustments to your watering times.
The Index represents Cambria’s recommended percentage setting
for the watering budget adjustment feature. During the irrigation
season, the Watering Index is recalculated to reflect the
landscape’s changing need for water. The controller’s
percentage adjust feature should be adjusted to match the current Index
value.
Your controller should be set so that it waters at 100% during the
hottest, driest month of the year. Around here, that's July. Then,
check the Cambria Watering Index once a week and set the percentage
adjustment to match. This will then adjust the run times of your
controller accordingly.
Why is this weekly adjustment important?
Weather conditions change constantly and watering times should be
changed to compensate. You can save a considerable amount of water by
adjusting your controller via the Watering Index. Reducing your water
use will reduce your water bill and help us conserve limited water
resources.
How is the Watering Index calculated?
The Watering Index is based on evapotranspiration (ET) data. ET estimates the
loss of water evaporated from the soil and transpired by plants.
ET is calculated by the
Cambria weather station from solar radiation, air temperature,
relative humidity, and wind velocity. ET values are primarily dependent
on the amount of solar radiation and wind. Your watering schedule should be
designed to replace the amount of water lost via ET.
The Cambria implementation of the Watering Index compares the
current running 7 day ET total for the with the highest weekly
average ET value recorded over the last 10 years. The historical high
occurs in July and equates to 100 percent on the Index. The concept
of the Watering Index was developed by Mr. John Wynn, of the State of California Department of Water Resources.
This "Modified" Watering Index is an enhancement of the
original DWR Watering Index. It calculates the Index normally,
and then subtracts the last 7 days running total of local rainfall from
it.
Keep in mind that Cambria recalculates the Watering Index daily at
about 12:15 AM, and that it will change slightly from day to day.
However, you should only need to adjust your controller once every week or
two, depending on the weather and how fast the index changes.
What if my controller is set at the suggested Index value and my plants look stressed?
The Watering Index is a guide. It's calculated from data gathered at
the Cambria weather station site at the Fire Station on Burton Drive, but should be
useful up and down the coast from Cayucos to San Simeon. The Index provides you with data on the
percentage adjustments for your controller. However you must pay attention to the health
of your landscape and the operation of your irrigation system (i.e.
broken pipes or irrigation heads). If you have confirmed that your
irrigation system is operating correctly and have set your percentage
adjust feature at the weekly Index value and your plants still look
stressed, increase the base runtimes (the "100%" value) for the
individual stations that look stressed by 5 minutes.
Common signs of plant stress are droopy leaves, or a grayish blue
tinge to your grass, or grass that stays flat after being stepped on.
After making the adjustment, wait several days to see if the stress
disappears. If signs of stress remain, increase the adjust feature up
another five minutes. Be aware that plants suffering from overwatering
may show similar signs as under watered plants – leaves will wilt
and yellow and sometimes fall off.
Will the Cambria Watering Index ever be greater than 100 percent?
Sure. If there are exceptionally hot and dry periods, or periods of high winds during the year,
the Watering Index may exceed 100 percent. Your percentage adjust
feature can be set for values greater than 100 percent
Weather Station Installation and
Web Site by Innovative
Concepts,
San Luis Obispo, CA , and Cambria CSD.com