This is not just in these areas. The number of States that have declared "Emergency Drought Conditions" in the past few years is much greater.
Most of this lack of water is due to mismanagement of building sites.
The "COMET" a n upper level group of the NOAA released a document last year that spoke of the changes to the environment caused by the hardening of the ground structure by compacting for multistory buildings and lack of ground absorption due to channeling the run off to concrete sewers for reprocessing as sewage.
Here in eastern NC the Capital of NC is Raleigh and it is between two rivers and a Lake. It is still under water rationing even after two floods and many storms.
The problem is that when you build an apartment building instead of creating sumps to allow water to sink into the soil the city wants "ALL" of the run-off to run into the Sewage return system.
The reason is money.
When a City removes water from an EPA recognized water source like a river it must return the same quantity of treated water or pay a fine. Then there is the Al Gore storm water treatment act. This penalizes all cities that allow Concrete driveways. This results in an added tax on the homeowners for treating storm water to remove man-made chemicals. So the cities add a few mils to this tax to help pay for the treatment and profit.
The alternative would be to make the Contractors and builders create in ground sumps and that would lead to less building, less inspections, less taxes... you get the point.
This is why many people have started to capture the rain off their roofs and store it for use on their yards on no watering days.