Gedeon Dagan, groundwater ambassador

Gedeon Dagan, a professor of engineering at Israel's Tel Aviv University, will receive the 1998 Stockholm Water prize from King Carl XVI Gustaf of Sweden later this month. Dagan was selected for the award for his research on the relationship between pollutants, subsurface formations, transport processes, and groundwater. In this article, we take a look at Dagan's life and work.

Gedeon Dagan - the 1998 Stockholm Water Prize winner.

Gedeon Dagan - the 1998 Stockholm Water Prize winner.

To Gedeon Dagan, the water in Niagara Falls, Lake Victoria, and the Amazon river is nothing more than a drop in a bucket.

Gedeon Dagan - the 1998 Stockholm Water Prize winner.

While the world's surface water sources may sometimes be spectacular, the Israeli hydrologist knows that they are tiny compared to the water resources stored underground. In fact, on a volume basis at each given instant, he notes that some 97% of all the freshwater found on Earth is stored underground (excluding water locked in the polar ice caps and glaciers).

Dagan - an engineering professor at Tel Aviv University - has made groundwater the central focus of a distinguished 40-year career.

In a way, though, winning the Water Prize offers a new beginning. "When I heard about the Prize, I felt tremendous personal satisfaction," the Romanian-born professor says. "Not just because it was a recognition of the groundwater field in general, but also because it was a recognition of all the other professionals working – sometimes in relative obscurity – in groundwater. Now I am an ambassador for this important issue."

As an ambassador, Dagan hopes to draw even more attention to groundwater. Compared to lakes, rivers, and streams, the time scales of groundwater flow are long. It may take years or even decades for water to find its way down through the soil to reach the water table. Once there, water may remain underground for tens or even thousands of years before it reappears in the surface. Some of the water in the chalk aquifer that lies under London fell as rain in the last ice age.

According to one estimate, on average the water vapour in the atmosphere is renewed every eight days, stream water every 16 days, soil moisture once a year, swamp water every five years, and lake water every 17 years. The average for groundwater is 1400 years, but the recycle time for some aquifers is much longer than this.

The concept of groundwater as a subsurface 'water body' harbouring an ecosystem is difficult and not yet well developed. "When water in rivers and lakes becomes polluted," Dagan says, "the effects of pollution are known relatively quickly. Because of this, people demand action, are supported by the media and get the attention of politicians, who are interested in taking steps for prevention or purification. Groundwater is hidden and therefore invisible for the user."

And there are lots of users, both in the developed and developing world. Estimates vary, but the proportion of potable water supply derived from groundwater is greater than 50% in much of the world. Overuse of groundwater – pumping it out faster than it is naturally recharged – is shortening the life of water availability in China, India, the western US, Mexico, the Middle East, and North Africa.

In short, this means that problems related to groundwater will take a long time to correct, which is why Dagan's work is so important.

In addition to the turnover time, groundwater protection is hindered by difficulties in observing and characterising the subsurface. Therefore, effective strategies for protecting and restoring groundwater quality require realistic predictions of the effects of different management options.

Dagan has opened a new field within geohydrology by coupling physical and biogeochemical processes along hetergeneous subsurface water pathways. By describing the subsurface formations using random functions, it is possible to determine the uncertainty attached to any analytical tool for groundwater management. This has proven to be very relevant when developing means for short- and long-term protection of water resources.

In particular, Dagan has been noted for his work in three areas: aquifer characterisation and monitoring; predictability; and design criteria.

For aquifer characterisation and monitoring, Dagan proposed a framework for statistical quantification of the effects of subsurface soil and rock variations on water quality.

On predictability, his theoretical results were the first to provide a rational basis for assessing the limitations of predictive modelling and quantifying prediction uncertainty related to subsurface pollution and restoration. Because of this, new avenues for more realistic analyses have opened in areas where prediction uncertainty is critical, such as risk assessment and cost-benefit analysis.

In design criteria, his theoretical basis for coupling hydrodynamic and biochemical processes in the heterogeneous subsurface environment enables more realistic pollution prevention and control measures to be set.

Recognition with the Water Prize is simply the most recent and prominent event in a career which began more than 40 years ago in Romania, where Dagan was born in 1932 and started his studies in hydraulic engineering and applied mathematics at Bucharest University.

In addition to the subject matter, one other practical reason motivated him to choose the subject of water engineering: he wanted very much to emigrate to Israel, and he heard that the subject was of great importance there.

"Because of the restrictions imposed by the communist regime reigning in Romania at that time, I couldn't fulfil my dream of moving to Israel until 1962," he says. Once he did, though, he started the journey that led to this year's Prize.

Having lived in Israel for more than 35 years, Dagan knows that protecting groundwater resources and avoiding further pollution is critically important for the country and the Middle East over the next 20 years.

Politics, of course, always offers the highest potential for volatility in Dagan's part of the world. "I believe there is enough water for Israelis and Palestinians, provided we work together to share and protect the resources and to develop new ones as the needs arise. Water is not the reason for any conflicts so far, but it has the potential to be used by politicians if tensions deepen."

And, as a technical expert, he is interested in co-operating with others in the region, as borne out by his participation in a recent Arab-Israeli joint research project.

The future? "Though the causes of pollution are well known, groundwater processes are very complex with respect to physical, chemical and biological parameters, and consequently are not well understood," Dagan says. "In these areas there is plenty of room for research. The ability to detect groundwater pollution has developed very much with new analytical methods, but it is important to look at these issues in developing countries, where for the moment most of the work is focused on simply finding enough water. One has to inform others in these countries about future problems related to uncontrolled exploitation of groundwater."

Dagan knows more needs to be done and says he will continue to develop and improve models but will also put research results into practice. In continuing his work, he should fit in well with previous winners of the Stockholm Water Prize.



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