Fresh water sources throughout the southwestern US are dwindling.

The Colorado basin states tried in the 1920s to stave off future fights over water by splitting it, 50-50, between the upper-basin states of Utah, New Mexico, Colorado and Wyoming and the lower-basin states of Arizona, Nevada and California.

In fact, the deal underestimated how much water the fast-growing lower-basin states would need. During most of the wet 20th century, however, the river usually produced more than enough water to offset any shortage.

Now, the gap between need and supply is becoming untenable.

Lake Mead currently stands about 1,106 feet above sea level, and is expected to drop 20 feet in 2014. A continued decline would introduce a new set of problems: At 1,075 feet, rationing begins; at 1,050 feet, a more drastic rationing regime kicks in, and the uppermost water intake for Las Vegas shuts down. At 1,025 feet, rationing grows more draconian; at 1,000 feet, a second Las Vegas intake runs dry.

Read the article. Not an easy problem to solve.