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Using Drip Irrigation In A Young Apple Tree Garden

Packhouses help growers out

Elgin packhouses empowered growers to irrigate their orchards during load-shedding. By Anna Mouton

Two Elgin packhouses — Fruitways and Kromco — assisted growers this past season by providing two generators to the Groenland Water User Association (GWUA). To understand how loadshedding affects irrigation, Hortgro spoke with GWUA chair Richard Moss and board member Ian Cunningham.

The lifeblood of the Elgin Valley

Commercial fruit production in the Elgin Valley relies on irrigation. Much of the water is supplied from the Eikenhof Dam through a network of about 80 km of pipes. “It’s the lifeblood of the valley,” says Cunningham, himself a deciduous-fruit grower.

The Eikenhof Dam lies just above Grabouw on the Palmiet River. It was originally built by farmers and opened in 1977. Today the dam is managed by GWUA, while the pipe system falls under Subdistrict 1, the body which replaced the old irrigation board. Five pump stations help move water around the valley.

“The system is designed to deliver water 24 hours a day, seven days a week,” says Moss. “We need to pump flat out just to give everybody their normal water allocation during non-loadshedding. If we lose time during loadshedding, we can never catch up.”

In addition to the 2–4 hours of loadshedding, Moss explains that another two hours are spent stopping and restarting the system.

“We shut down the pumps 20 minutes before loadshedding,” he says. “We have software that controls the whole system and reads the Eskom tables so that it can stop the pumps in an orderly fashion.”

Without a controlled shutdown, the pumps would stop abruptly when the power goes off, which risks damaging the pumps and the pipes due to hydraulic shock — also called water hammer. “If you flick the switch off on a pump while it’s running, it’s the same as slamming a valve closed,” elaborates Moss. The water in the system has momentum but nowhere to go, resulting in a pressure wave that can burst pipes.

During loadshedding, water drains from parts of the system under gravity to be replaced by air. Refilling the pipes too quickly after loadshedding can also burst pipes as the rapidly moving water compresses the air to dangerously high pressures.

“It takes us another hour and 40 minutes just to get the air out of the system,” says Moss. “During stage 4, where we get at least two load-shedding events a day, we lose four hours during loadshedding and another four starting and stopping — eight hours or one-third of the day.”

Packhouses lend a hand

Pump Station 2 is the heart that keeps the lifeblood of the Elgin Valley flowing. “The majority of the water goes through Pump Station 2,” says Moss. “About 4 500 cubes — 4.5 million litres — an hour. It’s huge.”

Gravity-fed from the Eikenhof Dam, Station 2 pushes water to a small reservoir that supplies most of the pipes running through the valley. From the reservoir, roughly a third of the water is again gravity-fed, while the remaining two-thirds require additional pressure to achieve sufficient flows. This is provided by booster pumps in Stations 3, 4, and 5.

(For those readers wondering about Pump Station 1, this is a low-volume station at Eikenhof Dam servicing several farms north of Grabouw.)

“We need electricity to pump water into the reservoir,” says Cunningham. “And when load-shedding happens, the reservoir drains within a matter of minutes.”

Keeping the reservoir full during loadshedding requires about 1 200 kW of generation capacity. During the past irrigation season, Fruitways lent GWUA a 500 kVA generator that could partially power three pumps. This was sufficient to keep the reservoir full enough so none of the lines emptied.

With Pump Station 2 operational — albeit not maximally — most lines were kept full by gravity. But one of the booster stations is at the bottom of a hill, therefore requiring an additional generator, which was lent to GWUA by Kromco. “We ran it during loadshedding to push water up and keep that line full,” says Moss.

“It was really incredibly generous of Fruitways and Kromco,” comments Cunningham. “We wouldn’t have gotten through the irrigation season without them.”

As packhouses, Fruitways and Kromco were able to spare the generators because the peak fruit-packing season only comes after the peak irrigation season. They charged GWUA nothing for using the generators.

“We were very happy to help out,” says Hein Keulder, CEO of the Fruitways Group, adding that the pack houses depend on the growers for fruit. “When good rains fell in late summer, the irrigation demands dropped, and we could move the generator back to our Valley pack house just in time for our peak packing weeks.”

The cost of load-shedding

Thanks to Fruitways and Kromco, GWUA managed to mitigate the worst effects of loadshedding but borrowing generators is not a long-term solution. GWUA is awaiting delivery of its own generators to power Pump Station 2. Pump Station 1 already has a generator.

Moss explains they’re still working out the optimal generation solution for the booster stations. “The bigger the generator, the higher the running costs,” he says. He estimates direct costs of about R7.50 per kWh for electricity produced by a big generator compared to around R1.50 per kWh for bulk Eskom power. That does not include buying the generator in the first place.

Meanwhile, GWUA has been upgrading infrastructure to cope with the erratic power supply, including installing variable-speed pumps. The system will also be adapted to allow automatic shutdown and start-up of pumps so that staff no longer need to get up at all hours of the night.

Electricity costs are the main contributor to water bills for GWUA members, so more expensive electricity will significantly impact growers already shaken by cost inflation. And paying for water is only part of their problem.

“I have to pump water from the supply line to dams on my farm. I irrigate from the dams,” says Cunningham. “With loadshedding, I can’t pump water into the dam or my orchards.”

Like many growers, he has purchased his own generator to ensure he can water his trees. “You don’t have a crop if you don’t have water,” he stresses.

Although GWUA could keep the water-supply system going this season, reduced pump capacity meant growers did not receive their full water allocations. “We had to push the water around to make sure everybody had enough to get them through,” says Moss. “We managed it based on who needed water at any time.”

The situation would have been much worse if not for good summer rains. “They were an absolute blessing,” says Cunningham. “We didn’t have to irrigate for well up to a week, and that bought us time to fill our dams.”

As things stand, he is optimistic about this season’s crop and grateful to Fruitways and Kromco. “Without them stepping in, we would have been in big trouble.”

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