How much water is currently available in the USA and your particular region?
I think if I was just beginning to think about gardening or small scale farming, I'd look at three forms of data that reported:
How much rainfall does my area get a year and in what seasons?
[link to water.weather.gov
How low are river levels right now?
[link to waterdata.usgs.gov
How low are ground water levels (water table)?
[link to groundwaterwatch.usgs.gov
There are many ways you can do that, but I have included links for each question.
This information will show you something that you already know: we're in the midst of a Great Drought.
36% of US citizens get their water from groundwater sources wells and aquifers. The rest rely upon lakes and rivers that increase or decrease based upon rainfall, snowmelt, humidity, and temperature.
Here's a map of the groundwater aquifers: places in which it collects. A well taps into that aquifer usually in a small way for individual use, but of course large ones for city municipalities.
[link to web.mit.edu
Now of course there is less rainfall in Winter in most places, though snow will fall offering a fraction of rainfall. So naturally it's dry now.
If you look at the other two pieces of the equation, I think we're in for a very rough Winter season. Even if we had to dig wells in Winter, a terrible situation, and/or gather from local river and lakes, the mass of people doing this with individual efforts would create a major drain of what's there, would be inefficient, would have a human cost, would be a sanitation nightmare, would translate into major health issues, etc. Those that are served by the Ogallala Aquifer: Colorado,Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming,
they are really getting hammered because they're using far and above what is going into it. They're in serious negative numbers, and it's estimated in a hundred years, at this rate they'll simply run out. They've diminished 197 million acre-feet of it.
I'm not certain that the study at that link took into account the projected human populationgrowth rate either, or industrial and agricultural demands. Livestock and additional crops needed would be the biggest drawdown most likely. I'm not a hydrologist.If you live in these states and you're not thinking about making modifications to acquire water, altering gardening techniques, having lots and lots of supplies, then really I don't know what else I can say to change your minds.
Looking at the region of the Mississippi, you'll see severe groundwater changes.
[link to www.businessweek.com
If you look at the link above, it notes that the link between the Ohio River and the Mississippi River is almost at historic lows, and that it may not be possible to navigate it past December 10th. This will create delays which affect grain prices due to delivery issues. How many other things move on this river?
Yes, railroads are thinking about expanding as a result of it. It will mean more trucks also to cope. The former will take a lot of time. The latter may put some truckers back to work.
Not to mention that, but the reason that some farmers have rich soil is from river silt. The river carries soil down and deposits it, just like ancient Egypt's river delta. These could also cause lower production of any crops grown in those regions. If the rivers is not renewing the soil by depositing it, then only the farmer's actions will increase its fertility. If you're farming in that area, you're going to have to adjust practices too.
I think a good critical thinker would be looking at all of these issues to determine if moving wouldn't be a good option for some people based upon water sources and changes to them.