The Sierra Nevada mountains provide California with about 30% of its water supply. On April 1st 2015, the Department of Water Resources did its annual analysis of the snowpack. It was declared ‘virtually gone‘…lowest since 1950. It was only about 6% of normal.
- The recent 2014-2015 winter was not the driest on record, but close.
- Temperatures this winter for California and the western states have been the warmest on record.
- Reservoirs in California are running well below average levels. They will drop quickly because of the lack of snow melt and rain.
- The dry winter conditions and heat are setting the stage for high-elevation fires this summer.
- The agriculture industry is facing unprecedented low levels of groundwater. Continued pumping is lowering ground and water levels which may never be regained even with possible future wet seasons.
- Power production in the southwest states by hydroelectric dams is reduced due to low water flows. Each monthly set of bars shows a decreased generation trend from the 2001-2011 average.
- Conditions for a weak El Niño have been officially declared. It is not expected to significantly improve the drought conditions of the southwest.
- It is not known how long this drought will last. In the past 1200 years, decades long mega-droughts have impacted the southwest several times according to paleo-climatologists.
- Climate change causes more extreme weather events such as heavy rainfall and snowfall. These extreme events are possible when winter rains do return to California and the western states. This raises the possibility of very damaging floods.
These points are unsettling. It is a very serious situation faced by the residents of these states. The effects spill over into the lives and pocketbooks of people in many other parts of the world.
Greater depth and detail can be found in this article by Bob Henson at Weather Undergound.
The agriculture and groundwater connection was discussed in this article by the New York Times April 5, 2015.