My understanding is that agriculture in the desert works because of all the sunlight, so if water is provided it ends up actually being really good for growing plants.
(also, I don't think the Central Valley is actually a desert?)
Similarly, agriculture in a swamp works because of all the water. So if soil and sunlight is provided it ends up actually being really good for growing plants.
When I think of swampy areas I'm familiar with, they don't get as much sunlight as desert areas. It's possible to provide water to many areas that don't have a lot, but increasing total sunlight hours isn't possible.
Sure you can, you just give them unlimited free electricity and shine light on them. Basically what we do with water to sustain agriculture in deserts.
