There's a fundamental energy demand for removing salt from seawater and creating drinkable water that can't be avoided. Hence, desalination is fundamentally tied to the price of energy. These costs can easily bankrupt cities that try to rely on desalination to meet demand (for example, California droughts cause hydropower to go offline right when water demand is highest). Using fossil fuels to power desalination in the global warming era is also a really bad idea.

It might work in certain locales (lots of sunshine plus solar panels, perhaps), but the costs will always be high, and it's going to be very uneconomical for agricultural-scale needs.

People seem to always forget about nuclear. Pairing nuclear plants with desalination is perfect because you also need water in most nuclear reactor designs.

That doesn't solve the problem of what to do with the salt and other chemicals removed via desalinization. You're left with literally toxic brine that has to be dumped somewhere, at the expense of the ecosystems you dump in.

https://www.scientificamerican.com/article/slaking-the-world...

There are solutions besides straight up dumping the brine. Technology is evolving to handle this as desalination becomes more common. Of course the easiest thing is dumping it so some regulation may be required.

To me the ideal of using technology like this is a brute force solution. I'm always suspect of the scientific credentials behind the permaculture movement but I suspect that they have got this one right. Slow water down high in the landscape, let it absorb into the ground, build leaky damn structures and many of the water security issues go away. I think this has been proven fairly well in a number of semi-arid areas such as parts of India.

> I think this has been proven fairly well in a number of semi-arid areas such as parts of India.

I've recently seen a video on YouTube where they did this. They dug a "hole"/artificial lake with a capacity of over, I think, 140 million litres.

They used that to create "a wet spot" which slowly started to transform the surrounding landscape. Plants, trees, bushes obviously started from around that lake but moved farther and farther from it as the soil became better.

This does not solve any problems with salt water, but it could possibly a solution for areas where there's "only" very little water available.

Also it seems like a lot of agricultural water use doesn’t actually get to the plants. It just goes around the roots and sinks into the ground.

Could we grow things like almond trees in large concrete basins and collect any water not used by the roots?

Ground infiltration is the least bad thing to happen.

Keeping the water near the surface just results in more evaporation loss, and side effects for soil quality like concentration of salts.

Water infiltrating the ground will keep the soil "primed" for water absorption and storage, and prevent runoff and erosion and flash flooding. (Think about watering a potted plant with completely dried out soil.)

Plus it will just go towards recharging the water table.

At least aggressive drip irrigation should be a default mode.

What about atmospheric water extraction/harvesting? Is it a viable alternative with current technology?

Not really, since water vapor must eliminate huge amounts of energy to turn back into liquid water - each kg of water vapor will dissipate 2.27MJ to turn into a kg of water at 100C. Since this is a thermodynamic limit, there's no enginerring around it.

Ostensibly, heat pumps could dual-purpose as AC and dehumidification, but if you have enough water for a heat pump, the condensation you collect probably isn't going to be very significant.

Edit: My point being you don't have to supply 2MJ of energy, you need to move it. That can be done for less.

> My point being you don't have to supply 2MJ of energy, you need to move it. That can be done for less.

Understood, but the point is still that you need to keep something cold enough for vapor to condense, while the condensation of 1 kg of water is dissipating enough heat to bring 5.4 kg of water from 0 to 100C. Even if just moving the heat around, there's just too much of it.

For remote locations without any other alternative. Mostly for drinking and high value uses, still very expensive.

It is already super cheap and transported automatically. We just need to catch more of it. Rainwater capture will be the next big thing. Right now our idea of rainwater capture is letting it go back into the ground. That's fine, it kinda worked but not really. Now we need to capture more. Finally, yes, maybe everyone should get an RV style toilet, have no dishwasher and get their pressure reduced to 30 PSI.