Socialism

Socialists brought more people to the west than the water supply can support.

"To find a clue about the real source of the problem, we need only look to the Times article itself:

Thanks to reservoirs large and small, scores of dams including colossi like Hoover and Glen Canyon, more than 1,000 miles of aqueducts and countless pumps, siphons, tunnels and diversions, the West had been thoroughly re-rivered and re-engineered.

Rain doesn’t fall much in the West, so to get water, the people need to go to the water in the rivers, or the water in the rivers needs to be shipped to the people. That’s where all those aqueducts and tunnels and diversions come in."

Reservoirs don't change how much water flows into the system, but it makes it appear the area has more water than it does.

"Water shortages occur in the West not because too many people are flushing their toilets too often, but because agriculture, heavily subsidized through cheap water made possible by the federal government, continues to grow crops in places that would never support agriculture on a similar scale in a free market. Indeed, agriculture uses well over 80 percent of all the water used in Western states, and most of that water is stored, pumped, and diverted using dams, pumps, and aqueducts paid for by the U.S. taxpayer.
As a result, growers don’t have to face the real-life costs of transporting water to their farms. They only need consider the subsidized price, which is far below what it would be in a private market. Consequently, water usage for growers across the West is much greater than what it would be were there a functioning market for water in the region."

Short-term demand is temporarily able to outstrip long-term supply.

"Naturally, the fact that taxpayers pay for all this does not mean that the taxpayers control the water. The most important resource in the West is in fact mostly controlled by Congress and the Bureau of Reclamation, and indirectly by growers and other special interests. Water is distributed in the West not by markets and market prices, but by the political process."

This creates a problem that cannot exist in a free market.

"Naturally, the fact that taxpayers pay for all this does not mean that the taxpayers control the water. The most important resource in the West is in fact mostly controlled by Congress and the Bureau of Reclamation, and indirectly by growers and other special interests. Water is distributed in the West not by markets and market prices, but by the political process.
In an arid place like the West, the political control of water translates to the political control of entire sectors of the economy. Writing in 2004, economist William Anderson noted:

No private firm would distribute a precious commodity like water in a desert in the way that the Bureau of Reclamation has done it. While the subsidized farms in the West are private, the federal government owns the main input that is needed for their crops: water. Thus, the term “private enterprise” here is meaningless, since the farms are wards of the state.

The fact that many farms are “wards of the state” as Anderson calls them, does not trouble the more influential growers much, as agricultural interests remain extremely influential in Western states, and they indirectly control most of the water."

It should bother everybody else.