Choosing fresh water or salt water for a man-made river
by Lev Nelik, Ph.D., P.E.
May 3, 2018

In the March 2018 issue of Pumps & Systems, I presented an overview of the water infrastructure in Israel. Although Israel is a small country, the geographical and topographical climates are extremely diverse. For example, when it snows in the north in the Hermon Mountains, you can go for a swim in the south near Eilat or Aqaba, Jordan.

Water is a major challenge in the Middle East, and Israel is no exception. Desalination plants are now growing in capacity and number, since there is no lack of salt water. Plans for major projects are in the works, including a joint venture between Israel, Jordan, Syria and Palestinian Authority for a major canal connecting the Dead Sea with the Red Sea. An oil transfer from Saudi Arabia through Israel to Europe is also a part of studies, as described in several publications, including the ones referenced below. Due to rapid drops from hills to valleys, this requires significant head pressures and numerous boosting pumping stations.

New Project

The city of Beer Sheva is in the middle of Israel with a population of 250,000 and is growing rapidly. It is essentially an oasis in the desert, and most of its water supply comes from wells and also by water pumped from the coastal desalination plants along the Mediterranean coast.

A recently designed 22-acre area lake is scheduled to “come online” shortly, and plans are underway to add a river to the project—an unusual addition to the desert landscape. A river in the desert is becoming a reality, with a big technical, technological and environment challenge.

river diagramImage 1. Concept view diagram (Images courtesy of the author)

The main question is a choice of either fresh (reuse) or salt water. Each option has advantages and disadvantages. Fresh water can be readily supplied from the reuse of the wastewater processing plants, but it could also be an attraction for mosquitoes, flies, etc. Salt water is an excellent disinfectant, but is very corrosive, increasing expenses for the equipment.

The saltwater option is to bring ocean water from the coastal town of Ashkelon via exiting pipelines belonging to the oil companies. These pipelines presently deliver oil from the port of Eilat in the south to coastal and central Israel, passing close by Beer Sheva. Once the initial volume to fill the river is delivered, the valves will be closed and only used for occasional, although significant, make up due to evaporation (approximately 6 percent per day). The water would fill the existing “wadi” (a dry water bed), which presently gets only a trivial amount of water during winter rains.

Geography Challenges

Although not an Amazon River by any stretch, this river will be unique and flow for approximately 3 kilometers (km), at a water speed around 0.1 meters per second (m/sec), with an average depth of 3 m and width of 50 m.

The terrain challenge is that although the land is relatively flat between the coast to Beer Sheva, it begins to incline rapidly from Beer Sheva toward the Dead Sea.

The average elevation difference from the western boundary of the river to the eastern is nearly 70 m.

Therefore, it would be necessary to complete a major landscape reconstruction with earth-moving equipment to decrease the local slope in the proximity of the river to about a 2 m slope along the 3 km river length. Once achieved, the parameters for the pumps would become:

  • river flow = 0.1 m/sec x (50x2) = 10 m3/sec = 36,000 m3/hr ~ 150,000 gallons per minute (gpm) rounded
  • head (the slope after excavation and terrain modification works) = 2 m ~ 6 feet
  • 10 vertical turbine pumps (VTP), 15,000 gpm each, 25 hp motors, 200 revolutions per minute (rpm)
  • total power and cost at 10 cents per kilowatt hour (kWh) = 15,000 x 6 / 3,960 x 0.90 = 250 hp = 200 kW, for a total of $150,000 yearly energy cost
  • holding/emergency tank = river volume = 3,000 x 50 x 2 = 300,000 m3 = 80 million gallons

Location Details

Beaches will be filled with white salt, a leftover product from the nearby Dead Sea Water Works, making it an attractive recreational site.

The river bed will be lined with half-split pipes and covered with plastic sheathing (to prevent ground leak-through) and also filled with the white salt, making it a smooth, white river bed. On top of that, a clear blue seawater will flow, with trees planted along the banks for a recreational city park.

river cross sectionImage 2. Salt for the river

The energy will be provided by the solar panel field. Beer Sheva is hot and sunny most days of the year, making a solar panel energy supply field an attractive commercial advantage.

Conclusion

In my next few columns, I will continue providing you with the latest pumping updates from the Middle East.

Incidentally, this project will be just the first of a series of similar designs currently in consideration in the Middle East. A similar project, but 10 times larger, is planned in Saudi Arabia in collaboration with their Israeli engineers capitalizing on the small-scale experience.

A pumping technology center in Israel provides some of the pump design evaluation and scaled modeling testing to optimize design efficiency and minimize energy consumption.

References

Nelik, L., “Middle East: What’s New with Pumping Challenges in Israel?Pumps & Systems magazine, March 2018

Nelik, L., “Pumps and Systems in Transcontinental Energy TransferPumps & Systems magazine, pp. 8-9, January 2010

Ahmad Joraid, The photovoltaic water pumping systems (PVWPS) Taibah University Publications, Saudi Arabia

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A QUIZ FOR READERS:

A single stage vertical pumps specific speed is Ns = 200 x √(15,000) / 60.75 = 6,400. The assumed pumps efficiency at the above calculations was 90 percent as a rough estimate.

Can you provide a more accurate evaluation, based on the Efficiency Calculator at the following link?

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