Why do so many redwood trees on the golf course appear to be
unhealthy?
Back in 1999 the City of San Jose contacted us about using
recycled water on the golf course. At that time, the federal government was
mandating a reduction in the amount of waste-water flowing out of the water
treatment plant and into San Francisco Bay.
The City was in the process of building a piping system to distribute
some of the water leaving the water treatment plant to several golf courses in
our area, including Silver Creek CC, The Ranch GC and the Villages G and CC.
We knew at the time that irrigating the golf course with
recycled water would present both positive and negative results. While we knew we would be guaranteed all the
water we would need during drought years, we also knew that recycled water is also
much higher in sodium and chloride, better known as table salt, than the
potable water we had been using. Our main concern was that the high salt levels
would adversely affect the annual bluegrass (poa annua), the primary grass type
growing on the golf course. Annual
bluegrass is also one of the most salt-sensitive grass species. We decided that
we would use recycled water to irrigate the entire golf course, except for the
greens, because we didn’t think the greens would survive being irrigated with
recycled water. As part of the project to irrigate the course with recycled
water, a new pump station was constructed on the course by San Jose Municipal
Water Company to pump the recycled water into the existing irrigation piping system.
A new piping system was then installed so that we could continue watering the
greens with potable water. We did have
some areas of annual bluegrass in the fairways that died after being irrigated
with recycled water. Fortunately the problem was limited and we were able to adapt
to the problem by planting bermudagrass in those areas where the annual
bluegrass was doing poorly.
The first few years we used recycled water, the water department
allowed us to water for a couple of months each summer with potable water. This
helped lower the salt levels in the soil. After a couple of years the water
department said they wanted us to use recycled water only.
Eventually it became apparent to us that the recycled water
was causing big problems for the redwood trees. Redwood trees all over Santa
Clara County were having similar problems when watered with recycled water. Santa
Clara Valley Water District and the City of San Jose just recently finished
construction of a reverse osmosis plant adjacent to the water treatment plant. Now,
as the recycled water comes out of the water treatment plant, about 30% of the
water is diverted to the reverse osmosis plant.
The reverse osmosis process removes almost all of the salt from the
water. When this “clean” water is blended back into the recycled water, the
salt levels drop by 30%.
Will the redwood trees be able to recover now that they are
being irrigated with water that has 30% less salt? I recently
hired two leading experts in the field of irrigating with recycled water to
look at what can be done to save the redwoods. They have not completed their analysis yet,
but they are not hopeful that the redwoods can be economically saved. Another huge factor in determining the
health of the redwood trees is how much rain we will get. If we have another
drought year, as we have had the past three years, it will affect the redwood
trees in two ways. First, good winter rains are needed to wash the salt deep down
into the soil beneath the roots of the trees, and second, the abundance of rain
also helps dilute the salt levels in the rootzone of the trees. We saw a big
spike in the number of distressed redwoods last year and an even bigger spike
in distressed redwoods this year due to the drought.
You may have noticed that the redwoods have started greening
up. Unfortunately this has nothing to do with the drop in the salt level of the
recycled water. Redwoods normally put out new growth at this time of year. Over
the past ten years we have seen what looks like dead redwoods suddenly turn
green in the spring. We probably won’t have a clear picture of the long-term
health of the redwoods for at least another year.
For this year we are thankful that we will have all the
water we need since there are no restrictions on our use of recycled water to
irrigate the golf course.
