July 14, 2012

Water woes causing a lonely death for palm oasis

Corn Springs palm trees. (BLM)
Written by James Cornett
Special to The Desert Sun

In the middle of our own Colorado Desert exists a very lonely palm oasis. Known as Corn Spring, it is one of the most remote palm oases anywhere in the Southwest desert. It lies about 100 miles east of Palm Springs and about 10 miles south of Interstate 10, in the middle of the Chuckwalla Mountains.

I first visited Corn Springs and its small palm grove in the early 1970s. At that time it was a lush oasis dominated by desert fan palms, the same species of palm that lines Palm Canyon Drive in downtown Palm Springs.

The desert fan palm (Washingtonia filifera) is unique in that of the 2,500 or so species of palm on our planet, it is the only one whose dead fronds typically adhere to the trunk throughout the life of the tree. It is the second most widely planted palm in yards and parks in our region. Its close cousin, the tall and skinny Mexican fan palm (Washingtonia robusta) is now, unfortunately, the most widely planted palm in the Coachella Valley. It does not usually show the characteristic fronds on the trunk.

Few palms at Corn Spring have dead fronds adhering to their trunks. In fact, few palms have any fronds at all, living or dead. The reason for this is the oasis is dying, one of the few palm oases in our desert that is expiring. This is strange since most palm oases in California, Nevada and Arizona are thriving as never before with dramatic increases in palm numbers compared with a half-century ago.

What gives with Corn Spring? Why are the palms dying?

Desert fan palms require lots of water and so are only found where water is at or near the surface; such places as desert springs, seeps, streams or rivers like the Colorado. In the desert, dying palms are inevitably a sign that the source of water is being exhausted or changing where it comes to the surface. One or the other of these explanations is happening at Corn Spring.

The Bureau of Land Management manages Corn Spring and most of the lands around it. The BLM placed a well at the oasis decades ago. Could it be that too much groundwater is being removed by the well? Not likely. The campground at the oasis is rarely used; most people bring in most of their water, hand pumped to the surface.

Tamarisk trees have been growing at the oases since at least 1980. Might the tamarisk trees be intercepting the groundwater with their roots before the palms get it? This could account for some water loss but palms usually crowd out tamarisk trees, not the other way around. Besides the palms and tamarisk trees have been living together for quite a while and for most of the time the palms were doing fine.

Most desert springs, such as Corn Spring, receive their water from the damming of underground flows by earth faults. Finely crushed soil (fault gouge) can be impermeable to water flow and groundwater may rise all the way to the surface. A fault has created the canyon in which Corn Spring lies. The damming of groundwater results in water rising to the surface at just the one place. Hundreds, perhaps thousands, of years ago desert fan palms seeds were brought to the spring, most likely by the ancestors of Cahuilla Indians. The seeds germinated and the young palms thrived in the warm climate of the Colorado Desert and in the moist soil at the spring.

Some time in the last 20 years or so, an earthquake resulted in a shifting of rock and alluvium along fault. It seems to have altered the movement of groundwater to the surface. Although some water was still available to the palms, most was not. Perhaps the underground dam was breached allowing the water to sink deeper into the earth.

An alternate explanation is that the aquifer (groundwater) was finite, filled during the last ice age when rainfall was more plentiful. With the drying out of the Southwest over the past 10,000 years, the aquifer is no longer sufficiently recharged and has become exhausted. No water is left for the palms and oasis slowly expires.

Whichever explanation is correct, the oasis is dying. Cutting down the tamarisk trees might help but will probably not alter the long-term prospects of the oasis.

James Cornett is a desert ecologist living in Palm Springs.