PAST: rising temperatures and droughts in Santa Barbara County

Drought severity in Santa Barbara County from 2000 until 2017, showing the landmark drought of 2014-2017. Darker colors represent worse droughts; higher values mean more of the county was in drought. Source: United States Drought Monitor.

---

​Climate changes and the local environment:

Average annual temperatures across California have been rising since the nineteenth century, a trend that has sharply accelerated since around 1970. Average temperatures across all seasons in Tulare County in south central California have mirrored that statewide pattern. As the county warmed, it suffered a series of severe droughts, which are usually defined as long-lasting moisture deficits that have environmental and social consequences. Droughts in the county involve three sources of water: surface water at low elevations, snow at high elevations, and groundwater buried below the surface. 

Precipitation in much of California has long varied by as much as 50% from year to year. Hotter temperatures, however, are increasing the rate of evaporation across California, including in Santa Barbara County. That has affected both mountain snow and lowland liquid water, and has made local droughts even longer and drier than they once were. One of the most severe droughts in the county's history recently began in February 2012 and lasted into 2017. The driest stretch of the drought started in February 2014 and endured until January 2017. It was part of a broader Californian drought that started in coastal areas several years earlier, and was up to 27% more likely to occur in our warmer climate. 
​
Longer, drier summers and an earlier snowmelt have caused drier forest conditions in southwest California, which has increased the amount of available kindling for wildfires to consume. These conditions have increased the size and duration of wildfires in California, and dramatically lengthened the wildfire season in Santa Barbara county. 

How we know: 

These reconstructions rely on several easy to use tools that are available online: the National Oceanic and Atmospheric Administration (NOAA) State Annual and Seasonal Time Series, the NOAA Weekly Palmer Drought Indices, the National Drought Mitigation Center's United States Drought Monitor, and the United States Geological Survey (USGS) interactive website. 

NOAA's State Annual and Seasonal Time Series relies largely on weather station measurements. NOAA's Palmer Drought Indices use a standard way of measuring drought that considers both water supply and demand in a soil moisture model. Negative values represent droughts, and positive values represent wet conditions. The United States Drought Monitor uses a number of drought indicators, including the Palmer Drought Indices, that consider both environmental and social manifestations of water shortages. The interactive tools made available by the USGS draw on open data provided by a range of United States government agencies, including the Army Corps of Engineers and the Bureau of Reclamation. 

Water levels in Cachuma reservoir responded to the Californian drought.

---

Human consequences: 

Droughts can sharply reduce the quantity of water in reservoirs and aquifers across California, which often supply water to local residents. Reservoirs, which collect precipitation, and aquifers, which are the groundwater storage spaces, both contribute to Santa Barbara’s water supply. This supply is crucial for both commercial and industrial use.

If global warming continues, Santa Barbara’s premium wine industry could be significantly affected. This is because distinct grape species can only thrive in specific temperature ranges. If Santa Barbara fails to produce grapes that can tolerate higher temperatures, then the decline in suitable land could be up to 20%. Wine is currently the third-most produced commodity in Santa Barbara county, and wine sales comprise nearly a tenth of the county's economy. 

One of the main water sources that supplies residents in Santa Barbara county is the Lake Cachuma reservoir. The reservoir supplies 85 percent of the water supply for over 250,000 residents of Goleta district in Santa Barbara county. Its available water supply plummeted during the California drought. As of October 1st 2017, it is still only 43% full. 

The lack of water in the Cachuma reservoir, in conjunction with the drought, will force Santa Barbara county to search for alternative water sources. Just recently, the county decided to reopen its desalination plant to supply more water to their residents. The reactivation of this plant cost the county an estimated $71 million, not including the cost of maintaining the plant. It will supply 3 million gallons of water per day to residents to cover 30% of the city’s water usage. In a warmer and drier future, such desperate measures may well be necessary across California. 

---

Article author: Madeline Lee, Georgetown University
Article editor: Dr. Dagomar Degroot, Georgetown University