IN THE GARDEN THE NEXT GENERATION IN AUTOMATIC SPRINKLERS.

Byline: JOSHUA SISKIN

Are you tired of reprogramming the time clock that controls your automatic sprinkler system? Are you frustrated by the sight of sprinklers watering after (or during) a rain? Are you concerned when water runs down your driveway every time your sprinklers come on? If you answered ``yes'' to one or more of the above, you will welcome the arrival of a new generation of sprinkler system time clocks.

By 2010, all new time clocks installed in California will be required to have self-programming and water-saving features. Soon, the sight of sprinklers watering in the rain will disappear.

The new technology begins with an understanding of how water is lost from the soil. Two factors cause soil to lose water: evaporation from the soil itself and transpiration from plants growing in it. Transpiration has been termed ``botanical sweating'' and describes the process whereby water is pulled out of soil by roots, transported up the trunk or stem, taken into the leaves and finally released or diffused into the outside air. Thus, evapotranspiration - ET - is the total amount of water lost from the soil-plant matrix.

ET varies with the weather and with the type of landscaping. ET increases when the weather warms and is greatest in lawns and in annual and perennial beds, while it decreases in cool or wet weather and in ground cover and shrub plantings.

It is easy to see that it makes no sense to apply more water than is lost through evapotranspiration, and this is where water savings are achieved with the new clocks. ET data, based on temperature, precipitation and type of landscaping, has been compiled over the years and has now been incorporated into the memory bank of the new ET time clocks.

Richard Angelo, who owns Stay Green Inc., and has been a landscape contractor in the San Fernando and Santa Clarita valleys for 35 years, did thorough research on the many new ET clocks before settling on the Aqua Conserve model. ``You program the clock for the month of July, when watering frequency is greatest,'' he explained, ``and you do not have to worry much about reprogramming the rest of the year.'' Using July watering time as a baseline, watering is automatically decreased by a fixed percentage, depending on the month, the rest of the year.

Dan Andrus, owner of All American Landscape in La Crescenta, has installed two dozen Weathermatic ET time clocks in the last few months, thanks to a rebate program of the Crescenta Valley Water District. If you live in La Cresenta or Montrose, or selected areas of Glendale and La Canada-Flintridge, you are entitled to a $225 rebate when you install an ET time clock of 12 stations or less, a $550 rebate for an ET clock with 13 stations, and a $1,100 rebate for a clock with 24 stations. Many water districts are currently offering rebates, including selected areas served by the Metropolitan Water District, especially in Orange County. Unfortunately, people residing in Los Angeles are not entitled to such rebates at the present time.

For each watering station, Andrus specifies type of landscape, type of soil and degree of slope. He does not have to make any decisions about how long he needs to water the different areas; once the data is supplied, the time clock does the rest.

Both the Aqua Conserve and Weathermatic models come with their own mini weather station, consisting of a thermometer and a rain gauge. There are other ET clocks that do not have these instruments and receive integrated weather data for the surrounding area via satellite. However, according to both Angelo and Andrus, the satellite systems cannot take into account the microclimate in a particular back yard and, therefore, are not as accurate as the models accompanied by thermometer and rain gauge.

Satellite systems also carry with them a $4 monthly service fee.