Planet Relations

There’s much talk about how climate change will affect weather patterns, causing more intense events such as hurricanes and tornadoes. In California, one consequence of the greenhouse gas buildup is a change in precipitation type; climate change is expected to cause a shift from snow to more rain during winter months (i.e., a diminished snowpack), and an earlier snowmelt.

While you may think that water is water, regardless of its physical state, this shift may have significant ramifications for water-capture infrastructure in the West. 

Reservoirs on 22 major rivers in the Sierras release winter waters to provide space behind the dams to prevent flooding from spring snowmelt. The snowmelt is then released in the late summer and fall to supply water to agribusiness in the Central Valley and cities like Los Angeles and San Francisco. According to the U.S. Geological Society (USGS), as much as 75 percent of water supplies in the western states are derived from snowmelt.

Researchers have identified a trend toward diminished snowpack and earlier snowmelt in western states, which may be related to global warming, and in precipitation form or timing.

According to the National Streamflow Information Program of the USGS:

Annual streamflow in most western rivers has come progressively earlier during the past several decades. …The long-term tendency of springtime streamflow (that fraction of overall flow that occurs from April to July) as a fraction of overall flow has declined during the 20th century in the central and northern Sierra Nevada. These results broadly reflect a regional trend toward warmer winters and springs during the same period.

If weather patterns shift, causing an increase of winter rains (as opposed to snow), runoff will occur earlier than normal. Water resource management of western rivers is based on the fact that much of the runoff to reservoirs occurs during the early parts of the warm season. The natural reservoirs provided by western snowfields will become less useful for water resource planning.

One approach, advocated by the State’s Governor, is to increase surface storage capacity. According to the state’s Department of Water Resources, the State and federal governments have funded five surface storage investigations.

Conservation groups such as the Sierra Nevada Alliance, are opposed to dam building and advocate for a comprehensive approach to accommodate the changes. The group's 4-point plan includes increased focus on Sierra meadow and forest restoration (i.e., water storage), dam re-operation (to better predict water releases); better floodplain management (to prevent damage during spring floods); and water conservation.

California and the West have a long history of tangled water politics. Climate change will force state leaders to examine all options when confronting a new era of reduced water availability. The first step for citizens is recognizing their individual responsibility.