Thais Tap Into Water Expertise : Hydrology: Worried about its sinking capital, delegation learns from county’s experience with replenishing wells.

Bangkok is sinking.

That’s why 13 Thai government officials dropped in on Ventura County water experts Thursday.

When Ventura County draws too much water from its wells, seawater invades the water supply. When Bangkok draws too much, the Thai capital sags--slipping another 3 to 10 centimeters deeper into the earth every year.

“Buildings still stand, but the floors are sinking,” said Prinya Putthapiban, a senior geologist with the Thai government’s Department of Mineral Resources. “Each year or so, you have to build another step or so to get into the buildings.”

Unlike Bangkok, the county has learned to control the problem by regulating ground-water pumping and by replenishing--or recharging--the underground wells.

Ventura County was the Royal Thai government ground-water committee’s last port of call on a three-day, breakneck tour through Southern California hosted by the U.S. Geological Survey. The delegates hit water treatment plants, ground-water recharge facilities and injection wells in Orange County, San Diego and Los Angeles.

On Thursday, the delegates bounced over gravel roads in a minibus while checking out the United Water Conservation District’s facility in Saticoy, a vast landscape of freshwater ponds and tubes jutting from the ground.

They shuffled along the Freeman Diversion dam built to collect water from the Santa Clara River and feed water back into the wells.

They peered into white tubes with red lips, the monitoring wells used to gauge the level of seawater intrusion into underground aquifers. And they lunched on turkey and tuna fish sandwiches.

“Everything that the district has in terms of data or management insight is available to you,” Dan Pinkerton, president of United’s board of directors, told the delegation gathered under a grove of eucalyptus trees.

Though Ventura County doesn’t have a large problem with land subsidence--or sinking--seawater intrusion has plagued the area for decades. Too much seawater can harm crops and affect the quality of drinking water.

A decade ago, a study warned that excessive ground-water pumping had caused more than 20 square miles of the Oxnard Plain aquifer to become contaminated by seawater intrusion. United has labored to place all five of the area’s five main aquifers in a “safe yield” position--meaning more fresh water goes into the aquifer than is pumped out.

Ground-water pumping restrictions and refill measures have worked in Ventura County, United officials say. Today, seawater intrusion threatens less than 10 square miles of the Oxnard Plain, United board member Lynn Maulhardt said.

“Relative to other counties, our county is very well under control,” Maulhardt said. “We are decades ahead on solving the problems.”

It was precisely this kind of expertise the Thai delegation traveled 8,276 miles to hear.

“Ground-water replenishment through injection wells and recharging ponds is something we can apply to our country,” said Vachi Ramnarong, project director with the Department of Mineral Resources, who works on Bangkok’s land subsidence problem. “It’s good for us to see how you manage your ground-water problems.”

Ramnarong said the Thai government’s ground-water committee started requiring permits to drill ground-water wells in 1977. Ground-water pumping regulation in central Bangkok, a city of more than 6 million people, has slowed the downtown’s descent. But Ramnarong said many Bangkok suburbs still draw more water from the ground than they return to the wells. Sinking there is still a big problem.

“We’re still far from the balance,” Ramnarong said. “We have to plan for the future.”