California is no stranger to droughts. In fact, dry years are more common than you might think. But how exactly does a drought impact the water supply across the state?
Whether you’re a homeowner, farmer, or just curious, knowing this ripple effect is key to knowing why water restrictions happen and how the entire system reacts when the rain stops falling.
Definition
First, let’s clarify what a drought really is. A drought isn’t just a hot, dry summer. It’s a prolonged period of below-average precipitation—rain or snow—that creates water shortages. In California, this usually means reduced snowpack in the Sierra Nevada, low reservoir levels, and dried-up rivers and streams.
And since California depends heavily on both surface water and snowmelt, a drought has serious consequences that stretch across every corner of the state.
Sources
Most of California’s water comes from three main sources:
- Snowpack in the Sierra Nevada
- Rivers and reservoirs (like the Sacramento and San Joaquin Rivers)
- Groundwater from aquifers
In normal years, snow melts in the spring and flows into reservoirs, supplying cities and farms throughout the dry summer. But in drought years, there’s less snow—and what little there is melts faster due to heat. That means less water makes it into the reservoirs and aqueducts that feed the entire state.
Storage
Reservoirs are like California’s water savings accounts. During wet years, the state stores as much water as possible to use in drier times. But when a drought drags on for multiple years, those “savings” run dry.
Here’s how drought impacts major water storage:
| Reservoir | Normal Capacity | Drought Impact |
|---|---|---|
| Shasta Lake | 4.5 million AF | Can drop to 25–35% of capacity |
| Oroville Reservoir | 3.5 million AF | Severely reduced in dry years |
| San Luis Reservoir | 2 million AF | Levels decline rapidly |
(AF = Acre-Feet, or how much water covers one acre of land at one foot deep)
With reservoirs shrinking, the state has to rely more on groundwater and emergency measures.
Agriculture
Farms are hit hard during droughts. Agriculture uses about 40% of California’s water supply, especially in the Central Valley, where crops like almonds, grapes, and tomatoes are grown.
When there’s not enough surface water, farmers pump more groundwater—or they leave land unplanted. This causes:
- Increased costs from groundwater pumping
- Falling groundwater levels
- Crop loss or reduced yields
- Job losses in farming communities
Some farmers even sell their water to cities for higher prices during extreme drought years.
Cities
Urban areas also feel the pressure, though usually after agriculture. Cities may face:
- Mandatory water restrictions
- Reduced lawn watering and car washing
- Water rate hikes to cover higher costs
- Increased reliance on recycled or desalinated water
In recent droughts, places like Los Angeles, San Diego, and the Bay Area ramped up conservation efforts and water reuse programs to deal with shortages.
Environment
Nature suffers too. During a drought, rivers and wetlands dry up, threatening fish, birds, and plants that depend on them.
- Salmon can’t migrate upstream to spawn
- Birds lose nesting grounds in dried-out wetlands
- Forests weaken, making them prone to wildfires and disease
- Wildlife compete with people for dwindling water resources
The state sometimes has to release water from reservoirs just to keep endangered species alive—reducing the water available for humans.
Groundwater
During a drought, everyone turns to groundwater—but it’s not unlimited. Over-pumping leads to problems like:
- Wells running dry
- Land subsidence (sinking)
- Long-term damage to aquifers
- Water quality issues
That’s why California passed the Sustainable Groundwater Management Act (SGMA) in 2014, which requires local agencies to manage and monitor groundwater use during dry periods.
Response
When a drought hits, California responds with a mix of emergency actions and long-term planning:
- Water conservation mandates
- Public awareness campaigns
- Funding for drought-resilient projects
- Water transfers between regions
- Investments in stormwater capture, desalination, and recycling
The goal is to stretch every drop and protect supplies for future years.
Droughts are a natural part of life in California, but their impact on the water supply can be deep and wide-ranging. From shrinking reservoirs to stressed ecosystems, every corner of the state feels the pressure.
That’s why conservation, planning, and innovation are more important than ever to weather the next dry spell—and the one after that.
FAQs
What causes droughts in California?
Long periods of low rainfall and snowpack cause droughts.
How do droughts affect farming?
Less water means crop loss and more groundwater pumping.
Can cities run out of water?
Yes, but they often impose restrictions to prevent it.
What is SGMA?
It’s a law to manage groundwater sustainably in California.
How are reservoirs affected?
They drop to dangerously low levels in dry years.
