Monday, February 6, 2017

How do California water officials define drought?

In following up on calls by state Sen. Jim Nielsen and others for Gov. Jerry Brown to declare an end to California's drought, I've asked state officials to define what constitutes a drought and how they know or determine that a drought is over. Nancy Vogel, a Department of Water Resources spokeswoman, points to Page 5 of this report on California droughts. She also offers a bit of an explanation.

An excerpt:
Drought is a function of impacts, which may be quite local. There’s no rulebook for when a drought is declared or rescinded. Local governments can declare drought emergencies, and California governors through the years have declared drought emergencies at both a statewide and a regional (such as Central Valley) level.

The National Oceanic and Atmospheric Administration and the U.S. Department of Agriculture map weekly drought conditions throughout the U.S., but their analysis is somewhat misleading in California. They take a short-term view of how drought is defined. The U.S. Drought Monitor doesn’t have the capacity to reflect all the drought impacts affecting the state. It’s not designed to accurately reflect conditions in a state like California that relies heavily on groundwater and an extensive system of infrastructure that moves water between regions. It doesn’t capture operational limitations on supplies, such as conveyance restrictions in the Sacramento-San Joaquin Delta or endangered species act restrictions there and elsewhere.

Our assessment of the state’s drought conditions is comprehensive, dynamic and considers a number of factors, including reservoirs, snowpack, and groundwater levels at the end of the rainy season.
We know from experience that storms can cease. You’ll recall, for example, after the previous drought declaration was ended in March 2011 – and the arrival of some storms in November and December 2012 – severe drought returned, leading to the driest four year period (and some of the warmest years) in California’s history.

In the last 10 water years, eight have been dry, one wet, one average. Although this year may end up being wet – it looks that way now -- we can't say whether it's just going to be one wet year in another string of dry ones.

Many Californians continue to experience the effects of drought and a number of Central Valley communities still depend on water tanks and bottled water. Lake Cachuma in Santa Barbara County is at just 12 percent capacity, and groundwater – source of at least a third of the supplies Californians use – will take much more than a few storms to be replenished in many areas.
For my full story on the subject, check soon.

No comments:

Post a Comment