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The Quest for Water Purity

The Quest for Water Purity

August 7, 2008

Desert & Water Research

A Ben-Gurion University researcher has a technique to monitor pollutants before they enter Israel’s aquifers, and JNF is building more reservoirs. Will the moves answer Israel’s water crisis?

Sede Boqer, Israel — Declining rainfall and what some contend is government mismanagement have lowered Israel’s aquifers to their lowest level ever and prompted Water Authority Director Uri Shani to announce “the worst water crisis in the nation’s history.”

To deal with it, he told reporters at a Tel Aviv press conference last month, the country would start drawing water from the tributaries that flow into Lake Kinneret. In addition, he said polluted wells would be purified, that existing desalination plants would increase output while new ones are built, and that water for gardening would be limited. The price of water for some uses is expected to nearly double.

Critics see this as no more than a stopgap rather than a long-term strategy. 

Naama Elad, a water expert at the Israel Union for Environmental Defense, told the Jerusalem Post that Israel’s wells and aquifers have been “polluted for years and the government has never fought to prevent contamination or treat it.”

But now a researcher at Ben-Gurion University of the Negev, Ofer Dahan, has developed a way to help to provide real-time feedback to those monitoring the infiltration of groundwater by pollutants before it reaches aquifers — groundwater that he called “the most important water source on earth.”

It had previously taken as long as 30 or 40 years for standard monitoring techniques to provide those results. The purity of water in aquifers is important, Dahan told a group of visiting journalists at his laboratory earlier this year, especially in “arid and semi-arid environments where it is the only source of water.”

The area that separates aquifers from the surface of the Earth is known as the vadose zone. Dahan said remediation efforts to treat some pollutants through biodegration may be successful in preventing the pollutants from reaching the aquifers.

Germs placed on the soil or injected into the ground “will take care of a lot of things,” Dahan said.

Chemicals added to fertilizer can offset other the pollutants. Although remediation techniques are known, evaluating their success has always been problematic due to a lack of real-time monitoring devices.

“It’s similar to treating a patient with a drug for an illness without having the ability to know the body’s response to the remedy,” Dahan said. His device, Dahan said, has the ability to monitor and make sure the right remediation steps have been taken.

“We provide the analysis, we do not prevent or do remediation,” he said.  Dahan said his device monitors the hydraulic and chemical states of the vadose zone and provides the feedback required for efficient remediation. The devices are placed on long, flexible sleeves that are inserted into holes drilled into the ground. The sleeves extend as long as 135 feet.

To get a 3-D picture of an area, several sets of sleeves are slipped into the ground in different directions.

Once in the ground, the monitoring equipment measures the vadose zone’s hydraulic properties. It also has the ability to sample soil water for chemical analysis. 

“The method may be used to measure the rate of water and contaminant propagation through the vadose zone and allow an accurate measurement of groundwater recharging or the pollution rate,” Dahan said.

Since developing this system in 2003, Dahan has helped establish several monitoring stations in Israel, Namibia, South Africa and Spain.

In the meantime, the Jewish National Fund, which has built nearly 220 reservoirs since 1981, has responded to the water crisis by announcing plans to build another five reservoirs in the next two years and another 15 within five years. This is according to Avinoam Binder, the chief emissary to JNF from Keren Kayemeth LeIsrael, of which JNF is a part.

Virtually all of JNF’s reservoirs are used to hold recycled wastewater, Binder said. He noted that JNF has also built some reservoirs in the Negev to catch the overflow from streams and rivers. Unlike water that is processed in desalination plants, he said, recycled sewage and floodwater is not pure enough for drinking.

Binder pointed out that water from the reservoirs in the Negev [the south of Israel] are used primarily by farmers who have fruit orchards. The water is not pure enough for vegetables such as cucumbers and lettuce, which have a high concentration of water.

“That’s why it is dangerous to buy fresh vegetables from the West Bank because they flood their fields with sewage water,” he said.

B’Tselem, the Israel-based human rights group that monitors Palestinian areas, reported last month that the continuing drought in the region combined with the policies of the Israeli government has compounded the water crisis in the West Bank. It contended that the average water consumption of Israelis is 3.5 times more than that of Palestinians.

The group pointed out that the per capita average water consumption of Palestinians is 66 liters per day, about two-thirds the minimum recommended by the World Health Organization. And in certain areas of the West Bank, it said water consumption is at a third of the Palestinian average — including water for livestock.

Binder pointed out that water from Lake Kinneret is an important source of drinking water for residents in the Negev. Lake Kinneret’s water comes from rainwater and snow that melts from the mountains in northern Israel.  But Dahan points out that although much attention is paid in Israel to the water level in Lake Kinneret, it supplies only 15 to 20 percent of the country’s water.

Dahan said that in Israel his equipment is being used to study one of the six reservoirs that have been built in the Arava Channel, the first of which was built 30 years ago. And it is already coming up with some startling findings.

Data collected with the vadose zone monitoring system under one of the reservoirs showed that the infiltration of groundwater by reservoir water was very limited because of a heavy build-up of silt on the floor of the reservoir.

Thus, Dahan said, it “may be claimed that water infiltration from the reservoirs to the groundwater is negligible and that water collected by the reservoirs is wasted since only small portions of it may be pumped for direct use.”

“The vadose zone monitoring system was also implemented in other projects such as land use impact on groundwater recharge,” he added. “In this project, the monitoring systems were installed under various land setups such as on agricultural land, dairy farms and urban settings such as city parks and parking lots.”

Among the system’s other uses, Dahan said, is that it can be placed beneath landfills to determine if there has been any leaching and in gas stations to see if there are leaks in in-ground storage tanks.

Dahan said he plans to market the probe, which he said would cost $20,000 to $30,000. But he noted that the cost is only a fraction of what it would cost if the problem were not caught in time.

It was widely believed that it took 30 to 50 years for pollutants to seep through the soil and into an aquifer. But Dahan said his research has found that it takes a few years.