They said that it was very easy for Israel to desalinate sea water, and provide for themselves in that manner.
Then I did a bit of googling, and I hit on this:
http://www.water-technology.net/projects/israel/The Ashkelon Desalination Plant.
"The new Ashkelon seawater reverse osmosis (SWRO) plant - the largest desalination plant of its kind in the world - commenced initial production in August 2005, less than 30 months after construction began. Initially running at around 30% to 40% capacity, it will ultimately provide an annual 100 million m³ of water,
roughly 5% to 6% of Israel's total water needs or around 15% of the country's domestic consumer demand."
Infrastructure of this sort if very vulnerable to attack, so it is not a completely viable strategy for correcting the water shortage that Israel undoubtedly suffers from. Additionally, there is the issue of Israel's geopolitical goals, which (I think) are in line with the USA's - to control the flow of oil of the Middle East, in light of the ascendancy of China and India. Israel's job appears to be to modify the balance in the region. Iran is quite powerful.
Therefore, you must ethnically cleanse people from an area. Native people have historically given validity to the most effective guerrilla movements: Hezbollah, Viet Cong, American Revolutionaries, African National Congress, The Maoist armies in China, the Tamils, the armies led by Camilo Cienfuegos in Cuba, etc.
So, to displace the shiite salt of the earth in southern Lebanon, you must do to them what you are doing to the Palestinians further south: Make them miserable, weaken them, crush them, make them die of thirst, etc, etc. And that is what appears to be going on.