We’ve been saying for months now that climate change will require California to add more storage capacity since the current system was designed for a certain amount of rain and a certain amount of snow to fall in the Sierra each year. (See here, here and here.) Since climate change implies there will be more rain and less snow in the future, the current balancing act can’t be maintained. That’s one of the reasons we believe Proposition 1, the water bond on the November ballot, is so important. Now the feds are sounding the alarm as well.

The Bureau of Reclamation, in a new report out this week that examines the effects of climate change on the Sacramento and San Joaquin river basins, says this:

Under current reservoir operational criteria, the seasonal shift in runoff has a negative impact on the ability to store water for later use. With earlier runoff and more precipitation occurring as rainfall, reservoirs may fill earlier and excess runoff may have to be released downstream to ensure adequate capacity for flood control purposes.

Under current reservoir operational criteria, the seasonal shift in runoff has a negative impact on the ability to store water for later use. With earlier runoff and more precipitation occurring as rainfall, reservoirs may fill earlier and excess runoff may have to be released downstream to ensure adequate capacity for flood control purposes.

In the accompanying press release, Interior Department Deputy Secretary Michael L. Connor said projected changes in temperature and precipitation, combined with a growing population, will have significant impacts on water supplies, water quality, fish and wildlife habitats, ecosystems, hydropower, recreation and flood control in California’s Central Valley this century.

In the accompanying press release, Interior Department Deputy Secretary Michael L. Connor said projected changes in temperature and precipitation, combined with a growing population, will have significant impacts on water supplies, water quality, fish and wildlife habitats, ecosystems, hydropower, recreation and flood control in California’s Central Valley this century.

The impacts will affect water users, water quality and the environment alike.

Due to the warming conditions, the runoff will increase in winter and decrease in spring as more precipitation falls as rain instead of snow. Reservoirs may fill earlier and excess runoff would have to be released earlier to ensure proper flood protection is maintained. This may lead to reduced storage in reservoirs when the summer irrigation season begins.

Water demands are projected to increase. Urban water use is expected to increase due to population increases in the Central Valley while agricultural uses are projected to decrease because of a decline in irrigated acreage and to a lesser extent the effects of increasing carbon dioxide.

Water quality may decline by the end of the century. Sea levels are predicted to rise up to 1.6 meters in that time frame which will lead to an increase in salinity in the Delta and a decline of habitat for fish and wildlife. River water temperatures may increase because cold water availability from reservoir storage would be reduced.

The food web in the Delta is projected to decline. Projected lower flows through the Delta and reduced cold water due to lower reservoir levels will make less water available for species, including endangered species such as migrating salmon.

The press release references a broader Sacramento and San Joaquin Basins Study, expected to be completed in 2015, which will provide additional analysis including the evaluation of adaptation strategies to mitigate impacts of climate change and meet future water demands. But Connor said something will need to be done:

This study confirms that the current status quo for water supply in California is not sustainable. Reclamation and its partners in California are already developing solutions to meet the projected imbalances between future supply and demand within the Central Valley.

Of course, Californians don’t have to wait until 2015 and beyond to take action. By voting for Proposition 1, the water bond on the November ballot, we can take an important first step towards increasing our water supply, which will help protect against climate change as well as future droughts.