To the last drop

Reclaiming deserts for farming. By Engela Duvenage.

Sewage or effluent is not waste. It is a treasure. If managed correctly, it can be sustainably used by the agricultural sector. If Israel can do it, South Africa can do it too. That was the challenge put to the local deciduous fruit sector by Israeli water expert Prof. Eilon Adar from the Zuckerberg Institute for Water Research at the Ben-Gurion University of the Negev.

Adar explained how sewage and effluent water from most major Israeli towns and cities is cleaned, fed into dedicated water grids, and then used by farmers for drip irrigation.

“In 2016 two-thirds of the water consumed by the agricultural sector in Israel was from reclaimed effluent
and we reclaim up to 89% of sewage water,” he noted. “Sewage is produced almost at a constant level all year around. It is nature. Knowing how to treat it makes it a sustainable source of water supply to the farming sector.”

The statement elicited uncomfortable giggles from participants at the Hortgro Science Technical Symposium.

“Don’t tell me you are afraid of your market’s reaction,” he pre-empted many participants’ sceptical responses. “Israel exports to central and western European markets and North America. We meet all the constraints of the European and US environmental protection agencies.”

Alternative water sources

Sewage water was not the only alternative water option that Adar presented to show how Israel manages to be the only country in the Middle East not to suffer from desertification.

“We produce more water than what God provides us with, because our demand is higher than what nature delivers,” noted Adar, who added that water management in Israel is a balancing act between how much water is available and which sources can be further accessed.

The world’s first drip irrigation system was developed in Israel in the early 1960s. Adar described the development of focused, efficient irrigation systems as an absolute necessity, given that the evaporation rate in the arid Middle East is about 12 to 14 millimetres of water per day. This equates to 12 to 14 litres of water loss per square metre.

“We simply cannot afford it,” stated Adar. “Drip irrigation has been a game changer and allows farmers to reach between 88% and 95% water-use efficiency.”

Five seawater desalination megaplants in the country have been operational since the mid-2000s, and in 2018 produced 655 million cubic metres of potable water. Brackish groundwater is also desalinated at various smaller inland plants.

Thanks to vast stretches of greenhouses, the country is able to produce food in desert areas with minimum water. Producers microharvest mist and rainwater, and plant crops modified to withstand brackish water. Fertiliser-rich water is recycled and reused.

Subsurface irrigation, more energy-efficient effluent treatment methods and responsive irrigation systems have been developed. The latter ensures that plants are only given the water that they need at any given time. Water requirements are calculated using advanced technology such as real-time photosynthesis metres and soil moisture sensors.

Preparing for worst-case scenarios

Israel’s focus on alternative water sources stretches back to its establishment in the late 1940s. The national water grid system has been developed since 1956. Israel’s national water carrier was inaugurated in 1964 and is nationalised. It allows water from different sources to be mixed and transferred across the country. Each source of water also carries a different cost which in turn drives water optimisation.

The substantial volume of water contained in the water grid is a valuable backup in case of trying times in the Middle East.

“Being in an arid, desert area, it became a kind of obsession to ensure that water scarcity is never a limiting factor to our economy. We have done everything we could, and still do, not to just survive but to flourish,” Adar emphasised.

Adar also noted that Israel already responded when the first red flags about climate change were raised, and has subsequently implemented pre-emptive measures.

“We work according to worst-case scenarios. We simply cannot afford a water shortage. We know the toll it will have on our economy,” he explained.

“It can be done if you have a vision, and are willing to invest and drive it,” Adar believes. “Our motto is that water will not hinder the local economy. We are motivated by the need to produce food for the world’s growing population.”

Bonus: Facts about water in Israel

• The average annual rainfall ranges from less than 50 mm in the south to 1 250 mm in the north.
• The Sea of Galilee is the only inland natural freshwater reservoir in the Middle East.
• All groundwater sources in aquifers are mapped and developed
• The annual renewable water in Israel amounts to about 1 400 cubic metres of water per person per year. This is less than 20% of the basic per capita requirement recommended by the World Bank.
• Only 24% of the water used for agriculture in Israel today is from fresh and desalinated sources. Another 8% is brackish water. The rest — 68% — comes from treated effluent.

Image: Intensive agriculture in the Israeli desert.