Module Code and Title
Assessment Outline – Final Report
Recommendation report comparing two types of water provision for a semi-arid
Region of your choosing
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Introduction
Israel is located in the Middle East, and has a total population of almost 10 million people. The country extends over approximately 22, 000 sq km. Its geography is mainly comprised of arid and semi-arid landscapes. Up to 60% of its total land mass is covered by the Negev Desert located in the south of the Country (Zaide, 2009 p.2). Israel is therefore faced with deficiency in the supply of water. Some of the water provisioning methods adopted in the country include desalination, ground water harvesting, rain water harvesting, and institution of very effective and efficient water management methods. Research by Zaide (2009 p. 4) shows that efficient use and management of water is more important and highly effective compared to increasing the supply. This paper seeks to evaluate the different methods of water provisioning in arid regions in Israel including desalination and ground water harvesting.
a. Desalination
Desalination is the process through which fresh water is extracted from sea water which has dissolved salts. It is implemented through reverse osmosis. In 2017, reverse osmosis comprised of over 70% of all sea water desalination methods in the world (Legislative Council Secretariat, 2017 p. 2). The sea water is first treated to remove any suspended materials. Water is then pumped at a very high pressure across semi permeable membranes that trap salt particles and molecules but allow water molecules to pass through. High pressure pumps push the water through several membranes allowing the dissolved salts to be left behind. The pure water is post-treated to alter the pH and add the necessary salts and ions in order to make the water ideal for drinking. All desalination plants in Israel make use of different modifications of this technique (Legislative Council Secretariat, 2017 p. 5). The plants which use this method include Ashkelon, Hadera, and Sorek.
Output
The Hadera plant in Israel began full operation in 2009, being the world’s largest SWRO (Sea Water Reverse Osmosis) plant. The plant has the capacity to produce 130 million cubic metres of water which represents approximately 80% of the country’s water supply needs (Egozy & Faigon, 2013 p. 12). The output is supplemented by desalinated water from the other SWRO plants in the country (Sorek and Ashkelon) which have a combined total production of 270 million cubic metres.
Cost
Desalination plants are very costly to build and operate and the margin for profitable output is limited. The Israeli government instituted a Build Own Operate Transfer (BOOT) method for the construction of the desalination plants to reduce costs. Pushing the water through the membranes is very energy intensive. The Energy costs constitutes about 30-40% of the total cost of the water (Garb, 2008 p. 6). Compared to thermal desalination methods, however, reverse osmosis is much more efficient and cost effective and is therefore the most preferred desalination method. According to Tenne (2010, p. 10), the average cost of operating a desalination facility in Israel per cubic meter of water is 3.5 kilowatt hours and US 65c.
Environmental and Social Impact
Unlike drinking water from other sources, sea water contains excessive amounts of boron. Boron is very harmful to the reproductive health of animals and plants and as such desalination plants must spend a lot of resources to ensure water is purified of boron (Garb, 2008 p. 8). Other toxic chemicals such as petroleum molecules or arsenic may permeate the membrane and contaminate the water. The brine that is produced needs to be carefully discarded into the sea to avoid it interfering with the sea ecosystem. Microbial organisms in the sea water may be pathogenic for example protozoa and bacterial and not all of them can be removed by desalination.
Due to the high energy requirements faced by desalination plants, majority of the plants are located next to energy sources. Many plants are powered by non-renewable energy sources such as natural gas in Ashkelon. In Israel, desalination provides a steady water supply reducing the country’s overreliance on water from West Bank (Garb, 2008 p. 12). Due to the large energy costs, a large portion of the cost of water is variable thus exposing the cost of water to overall variability of energy prices.
b. Ground Water Harvesting
Ground water forms the most important and abundant source of fresh water for animals and plants. It comprises over 65% of all fresh water available to animals, human beings and plants (Zaide, 2009 p. 6). In 2011, ground water comprised 35% of their total water supply in Israel. Ground water is a superior source because the water is free from harmful pathogenic microbes and does not require treatment for domestic and agricultural use. Ground water is completely clear and does not have turbidity. Moreover, ground water has a constant temperature as well as chemical composition (Zaide, 2009 p. 7).
Aquifers, which are the largest source of ground water, are not evenly distributed not are they always reachable even when available. They form when the geological and hydrological conditions favour their formation (Zaide, 2009 p. 8). In the event that the aquifer is found, the quality of water, its characteristics and rate of recharge of the aquifer determine whether or not the water will be available for human use.
Output
The introduction of wells to an aquifer destabilizes the dynamic equilibrium in the aquifer. This dynamic equilibrium dictates that when water is extracted from the aquifer, the aquifer corrects the disruption by increasing the rate of recharge, reducing the rate of discharge, or reducing the volume of water. Therefore, construction of wells to obtain ground water must put into consideration the recharge characteristics especially in arid areas where recharge from rainfall is estimated to comprise about 8% of the total rainfall received in the year. In Israel, the two major aquifers are the central aquifer and the mountain aquifer (Zaide, 2009 p. 7). Israeli aquifers have a total combined sustainable output of about 750 million cubic metres per year but they are overexploited to produce about 1100 million cubic metres.
Cost
In extracting ground water, the primary cost is the cost incurred by the energy that is spent in lifting the water from the aquifer to the surface. The estimated cost for pumping ground water is US$ 0.23 per a thousand gallons pumped per day. The overall cost is variable depending on the energy costs but it is generally cheaper than desalinated water (Garb Y, 2008, p. 9).
Environmental and Social Impact
As more and more water is pumped from the aquifer, the salinity of the water in the aquifer increases especially if the discharge is much larger than the recharge. Over 50% of water extracted from the ground is used in agriculture for irrigation purposes (Lloyd, 2009 p. 3). This poses a risk of the fertilizers and remains of pesticides seeping into the aquifer water thus contaminating it. Continued agricultural activities on the surface of aquifers, supported by the extraction of ground water, deteriorate the vegetative cover through overgrazing and deforestation. Moreover, pumping ground water has the effect of destabilizing the stream flows of a particular area.
Conclusion
The most common sources of water provisioning in arid areas such as Israel include desalination and groundwater harvesting. The use of ground water, being cheaper and more available, is more widespread than desalination which is more expensive and limited to specific areas. Groundwater sources and surface water sources should be used conjunctively for each to offset the drawbacks of the other.
Bibliography
Egozy, Y. & Faigon, M., 2013. The Operation Principle of the Hadera Seawater Desalination Plant and the Advantages of the Pressure Center Design, Jerusalem: The International Desalination Association World: Congress on Desalination.
Garb, Y., 2008. Desalination in Israel: Status, Prospects, and Contexts, Amman: Water Wisdom: Rugers University.
Legislative Council Secretariat, 2017. Seawater Desalination in Israel, Jerusalem: Legislative Council Secretariat.
Lloyd, J., 2009. Groundwater In Arid and Semi-Arid Areas, Birmingham: University of Birmingham.
Tenne, A., 2010. Sea Water Desalination in Israel: Planning, coping with difficulties and economic aspects of long-term risks/, Jerusalem: Water Desalination Administration.
Zaide, M., 2009. Drought and Arid Land Water Management, Jerusalem: Ministry of National Infrastructure.
