The Bureau of Reclamation has requested input from the public to resolve water supply and demand imbalances for the seven states, including California, using Colorado River water. The problem can be easily stated, the solutions not so easily. Using ten year running averages, the bureau shows that demand for Colorado River water has already outstripped supply and that this trend will continue and worsen.
They emphasize multiple approaches and solutions will be needed to solve the problem of too many people competing for too little water. The Colorado River no longer reaches the ocean. Many other rivers in the West are similarly dry. These simple facts alone show the magnitude of the problem.
The Colorado River Compact of 1922 set the basic rules for water sharing and conservation. It split the states into the Upper Division (Colorado, New Mexico, Utah and Wyoming) and the Lower Division (Nevada, Arizona, and California.) The Upper states are required to not overly deplete the flow of water into the Lower. Each group divides their water among themselves. Various new compacts further regulate and split the water and have led to massive projects such as Hoover Dam, Lake Powell, the Central Arizona Project, and large-scale commercial agriculture. Mexico is supposed to get some of the water, but given that the Colorado is mostly dry before it flows into there, it's difficult to see how they could be getting a full allocation.
Californians should note with alarm that their state has been using surplus water left over from other states since the Compact started. However, that surplus, if it even still exists, will almost certainly be going away soon, leaving California with even less water. In a 2001 agreement, California was given 15 years to find a solution. Nevada, especially Las Vegas, is also facing almost certain water shortages. They do not favor renegotiating water allocations in fear they could end up receiving less than now. However, Arizona Sen. John McCain has called for the compact to be renegotiated.
The Sacramento Delta faces similar challenges. The water wars between Central Valley agriculture and urban southern California are legendary and span decades. Conservation, desalination, and reclamation will certainly be part of the solution. Certainly using less water is an important first step. Lush lawns and golf courses in semi-arid areas and deserts will be going away. Desalination may seem an ideal solution. But it is very expensive and requires huge amounts of energy. But energy often requires large amounts of water to create, thus creating a vicious cycle of using water to generate power to get more water. Plus, no one really knows the effect on the oceans if, say, desalination was on a scale large enough to supply large cities. Reclamation will increasingly be a necessity. This means trapping water so it doesn't flow into the ocean in coastal areas and recycling wastewater with urine in it to be drinkable again. Some Texas towns are doing this now because of their extreme drought. While this may sound yucky, can we afford to not use and re-use all the water than we can?
The Bureau of Reclamation, as mentioned, is asking the public for ideas. At this point, no one really knows how this will play out or where the water will come from.