Israel recently inaugurated it's billion shekel reverse water carrier project[1], pumping desalinated water into the Sea of Galilee, Israel's largest freshwater lake[2]. It's being billed as an ecological move, aiming to restore the drying lake and saving the human and natural ecosystems that thrive on the lakes shores.
As such, hard nosed capitalists might be sceptical of the value of such a project. Between wet and dry periods the lakes surface level can range by up to 6m. With a surface area 170 million square metres, raising the lake's water level by just one metre costs at least 70 million dollars just in desalinated water, not including the significant capital and running costs for the reverse carrier itself. This might be a price worth paying to avoid the sea drying up, but not obviously so.
However when you understand[3] how the reverse water carrier actually slots into Israel's water system, suddenly the project doesn't just seem far cheaper - it's a clear net economic gain.
Desalination plants are extraordinarily expensive to build, at about $1000 per cubic metre per day of capacity, and CAPEX accounts for about 30-40% of total cost of desalinated water, despite their high electricity requirements. As such it is necessary to keep desalination plants constantly at nearly full capacity to minimise costs. This requires matching desalination build to average water demand, not peak, so we need a way to smooth demand.
Intraday demand variation is handled by a distributed system of small tanks and reservoirs, storing potable water immediately ready for use. If desalination plants are forced to close, as happened a few days ago due to large algae build up in the water, these tanks can also provide an emergency reserve. But because the water isn't cleaned between the tank and usage, it can't store water for more than a few days without health risks.
So to handle seasonal variation in demand (which is huge - the populated parts of Israel gets London's yearly rainfall all compressed into the winter, with essentially 0 rainfall between May and September), Israel needs another solution.
Historically this was done by recharging aquifers. This works well, but the aquifer is inherently limited in the rate at which it can fill and be emptied. With Israel planning to double desalination capacity between 2024 and 2032, aquifer storage alone will be insufficient. The sea of Galilee provides a huge natural reservoir that can be used to store surplus water and is already connected to the country's water grid. The ecological benefits come free.
Similarly, by keeping the Sea of Galilee at close to maximum capacity in wet periods, Israel can slowly draw it down during drought years, avoiding the need to overbuild desalination capacity to handle even the driest years.
So much for the Sea of Galilee. Exactly the same analysis applies to many drought stricken lakes across the world - using them as natural reservoirs can be far cheaper than building artificial ones[4], and throws in huge ecological benefits too.
The national water carrier, completed in 1964, transfers water from the Sea of Galilee to the centre and south of the country. The reverse water carrier takes water from the centre and south (where all the desalination plants are), back to the sea of Galilee.
This only applies to lakes with steep sides, where increasing volume doesn't significantly increase evaporation. While refilling the Salton Sea might be beneficial for other reasons, it makes for a pretty poor aquifer due to its very shallow profile.
Israel recently inaugurated it's billion shekel reverse water carrier project[1], pumping desalinated water into the Sea of Galilee, Israel's largest freshwater lake[2]. It's being billed as an ecological move, aiming to restore the drying lake and saving the human and natural ecosystems that thrive on the lakes shores.
As such, hard nosed capitalists might be sceptical of the value of such a project. Between wet and dry periods the lakes surface level can range by up to 6m. With a surface area 170 million square metres, raising the lake's water level by just one metre costs at least 70 million dollars just in desalinated water, not including the significant capital and running costs for the reverse carrier itself. This might be a price worth paying to avoid the sea drying up, but not obviously so.
However when you understand[3] how the reverse water carrier actually slots into Israel's water system, suddenly the project doesn't just seem far cheaper - it's a clear net economic gain.
Desalination plants are extraordinarily expensive to build, at about $1000 per cubic metre per day of capacity, and CAPEX accounts for about 30-40% of total cost of desalinated water, despite their high electricity requirements. As such it is necessary to keep desalination plants constantly at nearly full capacity to minimise costs. This requires matching desalination build to average water demand, not peak, so we need a way to smooth demand.
Intraday demand variation is handled by a distributed system of small tanks and reservoirs, storing potable water immediately ready for use. If desalination plants are forced to close, as happened a few days ago due to large algae build up in the water, these tanks can also provide an emergency reserve. But because the water isn't cleaned between the tank and usage, it can't store water for more than a few days without health risks.
So to handle seasonal variation in demand (which is huge - the populated parts of Israel gets London's yearly rainfall all compressed into the winter, with essentially 0 rainfall between May and September), Israel needs another solution.
Historically this was done by recharging aquifers. This works well, but the aquifer is inherently limited in the rate at which it can fill and be emptied. With Israel planning to double desalination capacity between 2024 and 2032, aquifer storage alone will be insufficient. The sea of Galilee provides a huge natural reservoir that can be used to store surplus water and is already connected to the country's water grid. The ecological benefits come free.
Similarly, by keeping the Sea of Galilee at close to maximum capacity in wet periods, Israel can slowly draw it down during drought years, avoiding the need to overbuild desalination capacity to handle even the driest years.
So much for the Sea of Galilee. Exactly the same analysis applies to many drought stricken lakes across the world - using them as natural reservoirs can be far cheaper than building artificial ones[4], and throws in huge ecological benefits too.
The national water carrier, completed in 1964, transfers water from the Sea of Galilee to the centre and south of the country. The reverse water carrier takes water from the centre and south (where all the desalination plants are), back to the sea of Galilee.
And only freshwater lake of any significant size.
I'm reading between the lines here - no-one explicitly says as much, but there are frequent allusions to the idea.
This only applies to lakes with steep sides, where increasing volume doesn't significantly increase evaporation. While refilling the Salton Sea might be beneficial for other reasons, it makes for a pretty poor aquifer due to its very shallow profile.