Sure, let's ignore the simple solution - stop consuming so much water - and jump to a high-tech, unknown impact, expensive, complex, expensive solution. What could go wrong?
I agree that it's a demand-side issue, but the solutions are not "simple".
There was already not enough water for the rights distributed in the 1922 Colorado River Compact [1]:
> The delegates figured allocations on hydrologic data from the Reclamation Bureau that indicated annual Colorado River flow at Lees Ferry to be 16.4 maf. In truth, however, Colorado River flow is a good deal less than that. Data from three centuries indicate an average flow of about 13.5 maf. Also, flows are highly erratic, ranging from 4.4 maf to over 22 maf.
> Built into the compact then, between what it promised and what the river was prepared to deliver, was water scarcity. There is not enough water to go around. As a result, water scarcity is the root of most of the disputes and problems subsequently arising over the compact and the Law of the River. It is a situation that links past and present Colorado River issues and will be an abiding concern in the future.
EDIT: You personally can make the choice to not live somewhere that will eventually face water scarcity [2].
[1] https://wrrc.arizona.edu/publications/arroyo-newsletter/shar... ("Sharing Colorado River Water: History, Public Policy and the Colorado River Compact")
[2] https://web.archive.org/web/20210721173013/https://i.imgur.c...
There are solutions, but they are not simple. You could relocate the main users, like agriculture and industrial users, to areas that are not as arid. This would also cause some migration of individuals. I mean, that is the driver of the scarcity - building cities in the desert.
It might not be palatable, but it will look better the worse things get.
Climate change is happening because of changes to atmospheric composition, solar panels aren't going to have a massive impact on that.
Austerity is the bad, risky idea that isn't a solution to anything.
Solar panel production, like all industrial activity, is pumping more CO2 into the atmosphere, not to mention other pollutants - from mining, factories, transport.
Besides, we need to replace all fossil fuel energy generation as quickly as possible with renewable energy generation. Adding any extra energy consumption makes this vital goal more remote.
Perhaps once 100% of energy is produced from renewable sources with 0 carbon emissions, we could think about starting to grow energy consumption again. Before that, thinking about huge new industries like this is completely irresponsible.
While austerity as a solution to monetary crises is completely counter-productive and a non-solution, it is unfortunately mandatory to avert the worse effects of the climate crisis. We have run out of time entirely, unfortunately, ignoring and hiding this crisis for the past 50 years. Stagnating and even reducing consumption is the only possible response today that can prevent the worse effects of global warming.
...I could see how the residents of those latter states would not be too happy with that solution, though. But it's not like the Federal Government isn't already constantly picking favorites for subsidies (see ethanol, oil, etc.).
The first step would be defanging whatever legal machinery HOA's use to ensure that you keep up with the Joneses re: how much water you can afford to waste.
For example, many people will fight the industrial and agricultural water use tax because their jobs depend on it. It would force people out of that area when those jobs dry up, just as the mandatory changes would.
1. Desalination
2. Purification
3. Distribution
There would be no shortage of fresh water on earth if we simply put resources into solving these three problems.
If we want any semblance of current society to keep chugging along 50-100 years from now, we need to reduce our production of almost everything, energy most of all. There is simply no other solution to stop catastrophic global warming.
But it seems one way or the other these shifts are inevitable, either by choice or it left unaddressed the other way as a natural consequence and with much greater suffering. Same with water use in arid areas, it's either restricted today or ultimately gone tomorrow.
I guess the approach of burying our heads in the sand can be at least assured of an increasing sand supply to support it.
Harnessing the sun's energy and applying it towards water desalination and distribution would allow us to grow all sort of plants (including trees) in areas that would otherwise be unable to sustain plant growth.
Plants are composed largely of carbon that is extracted from the air, so the more plants you can grow, the closer we get to solving global warming.
Harnessing solar energy is not free - you still need to build solar panels or other kinds of solar plants. Producing these requires metals that need to be mined, forged and transported. Solar energy only works for half the day, and is only plentiful part of the year.
Not to mention, today we need to decommission all fossil fuels in the world and replace them with renewables, also covering the energy needs of emerging countries. So while in some distant future of 100% renewables we could contemplate desalination, we can't spare any energy today towards new industries.
Even so, it is unlikely that we could replace all of our current energy consumption with renewables, given the huge problems with variability, in the foreseeable future.