I think what's not discussed is that most of this water ends up back into the ground and eventually back into a river. In some ways it even helps regulate river flow. Perhaps one improvement could not not allowing irrigation during from 8am to 4pm or something to reduce the amount of evaporation
I probably have no idea what I am talking about, but I think the time of day plants are irrigated is quite important.
Hypothetically, if you were to water right after the sun goes down, or when the sun is going down, there would be reduced evaporation. But, at the same time, the roots would be sitting in a wet environment overnight, which encourages things like rot and fungal infections, as well as bugs and such.
Again, I'm not a commercial agriculture guy...just a home tomato grower...watering in the morning right before the sun comes up seems to be the consensus, and I have never heard of anyone watering any plant or crop, for that matter, during non peak times.
I would assume evaporation is directly correlated with the surface area the water is spread on. Spreading water on farmland as opposed letting the water flow naturally into the Great Salt Lake is going to increase the effective surface area of the water.
Additionally, plants are pretty effective at pulling water out of the ground and releasing it into the air, so the agriculture aspect increases evaporation as well.
Both go back to the same place though. It doesn't matter if the water evaporates, or trickles down to groundwater, it's the same. If it evaporates it goes to the clouds, and then comes back down as rain, and eventually back into the groundwater.
The real problem is the water that is shipped out in the crops. That's why people say that Isreal is exporting all its water in the form of watermelons.
