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Comment by mlyle | Hacker News Reader

Right now, many farmers spend under $100 per acre-foot of water; 80% of non-environmental water goes to agriculture.

Water prices in urban areas are $1000 per acre-foot of water, because distribution is expensive. Desalination of brackish water can cost $1200-1500 per acre foot, and moderate improvements in costs could make desalination economically viable for urban water.

But it would require a truly massive improvement to be competitive for agricultural water use, and because most use of water is agricultural, we can only reap small benefits from desalination.

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Not to mention that we'd need to pump those millions of acre-feet uphill into the various agricultural regions. Some are lower lying but if California is serious about its GHG targets, it won't be building the massive power stations required to pump all of that water in addition to desalinating it.

Assuming the the other challenges can be met, me solution to distribution is to use desalinated water to fill up underground aquifers. The other option is simply to move agriculture closer to the coasts.

The Central Valley aquifer does not extend to the coast and is poorly connected to the coastal aquifier: https://www.usgs.gov/mission-areas/water-resources/science/c...

There is not enough flat, cultivatable land closer to the coasts to move much agriculture out of the central valley towards the coast, even if desal'd water was free.

Desalination allows the now unused surface water to be collected and diverted further upstream, slowing the decline of upstream aquifers.

For the upstream cities that use the Colorado River this could be quite beneficial.

But now we are talking about building a tunnel rather than an aqueduct. It isn’t weird to drill water tunnels for a hundred or so miles.

Other than the fact that this is even more capex and opex that will exceed any economic use of water in agriculture.

Sure, either desalination must become more energy efficient or energy must become cheaper for it to be usable in agriculture (well, the third option is that such food becomes a lot more expensive). Either of those seems hard but not impossible.

Power is only about 40% of OPEX of desal plants and very little of CAPEX. Even if energy were free, and there were brackish water right next to the farmers, you're not hitting the water prices above.

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