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only the salts that must be leached, but also various other

contaminants, contained in the water, added in agricultural

processes (fertilizers, pesticides and herbicides), or mobilized

from soil and subsoil.”

Other leading Israeli irrigation researchers, (such as Shmuel

Assouline, David Russo, Avner Silber and Dani Or) also began

to speak up about the issue, citing mounting evidence that

various aspects of soil hydrology are negatively affected by

wastewater reuse. Damage is the result of increased loadings

of organic matter, surfactants, nutrients, and subsequent

interactions with the soil.

Cognizant of the dangers, Israel continues to make signifi-

cant efforts to reduce salinity in its drinking water sources.

Regulations prevent the release of the salts used by kosher

slaughter houses from reaching municipal waste streams;

desalination provides an increasing fraction of drinking water,

reducing the salinity in the resulting sewage. But wastewater is

still a relatively saline source for irrigation, requiring copious

amounts of water for leaching out residues. When Avner

Silber and his colleagues compared irrigation with conven-

tional water sources to irrigation with water where salts were

removed via desalination prior to delivering to banana crops,

the results were compelling: not only did desalination obviate

salt leaching and the risk of salinization of underlying water

resources — it also improved yields and fruit quality.

Based on this research, academic and government research-

ers are openly recommending that desalinated water be

considered as a viable water source for irrigation. Given the

high energy demands and greenhouse gas emissions associ-

ated with desalination, a truly sustainable irrigation policy

may require solar energy systems to provide the electricity for

desalination processes.

The question is: Can farmers afford to pay for such high

quality water? Many agricultural experts argue that conven-

tional crops will not be profitable if they rely on desalinated

water, which in Israel ranges between 55 and 65 cents per

cubic metre (1,000 litres). Onions, carrots and potatoes would

be losing propositions; for tomatoes and peppers the economic

calculous is tenuous. Surely orchards in the drylands cannot

compete with groves that enjoy rain-fed conditions.

Based on Israel’s experience, certain implications for other

water-scarce countries are already clear: drip irrigation should

be a central component in any agricultural production strat-

egy. It is simply irresponsible to continue to use flood, furrow

and sprinkler irrigation when drip irrigation systems offer

such clear agronomic and environmental advantages. At the

same time, if a country with croplands in arid or semi-arid

regions wishes to sustain irrigated agriculture over the long

term, it must ensure an extremely high quality of water and

ultimately seek to utilize desalinated water sources. Sooner or

later, massive utilization of effluents will lead to salinization

and eventually force such a transition.

Farmers using desalinated water may not be able to compete

on world markets, so countries will need to consider subsi-

dizing water produced for irrigation. Moreover, if expansion

of dryland agriculture is not to compromise climate change

mitigation efforts, renewable energy should be integrated

in desalination processes. Finally, the Israeli experience

suggests that extensive wastewater reuse should only be seen

as a temporary exigency and a transition stage in a country’s

agricultural evolution. The well-documented, deleterious

environmental impacts are clear and disturbing, sending a

clear message that effluent recycling in the drylands is funda-

mentally unsustainable.

A Jojoba plantation at Hatzerim Kibbutz — 12 years of subsurface irrigation and going strong

Image: Naty Barak

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