Most deserts have life, which you would kill. But for sandy deserts, have you never built a sand castle?

The reasons are legion, starting with the fact that it wouldn’t work.

Most land based plants would die if fed saltwater.

The water would in most cases sink away below the surface too.

Salt.

If the area’s enviroment didn’t have it to start with adding it will kill off whatever lives there.

Also? Generally there’s a reason it’s a desert (lack of rainfall,) and is itself (usually) a vibrant ecosystem.

It’s been done before (though not intentionally at first), at the Salton Sea.

And the results weren’t that bad (granted possibly a smaller scale than some are imagining when they forecast doom).

ppic.org/…/the-troubled-history-and-uncertain-fut…

But the problem is any deserts are deserts for a reason: lack of rainfall and/or natural inflow from rainwater upstream. The result is that you have to keep pumping in tons of water and/or rely on agricultural runoff which is nutrient-depleted and usually full of chemicals.

Read the rest of the linked article for what’s going on with that one.

All these people saying “salt!”

I’d like to inquire how much water you think we’d need to pump how far, and then tell you the real number is way, way higher.

Do you own any desert?

OK then go on and terraform it. But be careful, because it goes wrong more often than right.

The sheer volume of water that moves through even a small creek is shockingly massive.

The amount of water held in an aquifer is astounding.

The soils required for agriculture and general growing plants (ones that hold water and nutriet) specifically are lacking or depleted in deserts.

So… it’s a literal pipe dream.

First off, the water would need to be desalinated or you would ensure the land would be unsuitable for farming (and really growing anything) for generations.

Also, sand doesn’t hold water. In fact, when planting trees and other bushes, if you want more drainage, you typically add rocks and sand.

Second, most plants need non-sandy soil to grow on (palm trees and other beach bushes and plants aside) though those grow in areas that have lots of rain already.

Thirdly, the soil will need bacteria to aid the plants in obtaining nutrients and breaking down waste (dead leaves, dead plantlife, etc).

The way to do it is to look at a couple of projects that are fighting against desertification in Africa:

You’ll notice that many of these projects start at the edges of deserts. Instead of relying on pumping water onto sandy soil (which would just suck up the water as sand doesn’t hold water that well) they focus on extending the non desert ecosystem onto the desert so that the new soil will absorb water better, the weather over the newly terraformed area will be less dry, and it will eventually be self sustaining.

Were you planning on desalinating the seawater first? Because that requires an immense amount of energy to do, and we haven’t even touched on the topic of the energy required to move water from one place to another.

If you weren’t planning on desalinating the seawater, then the salt will definitely destroy whatever nutrients the desert sand might have had, rendering seawater irrigation completely pointless.