Water & Drought Water Storage & Supply

Water Storage & Supply

Reads at about grade 5Both sides shown8 sources cited

This is the debate over how California saves and moves its water -- build more dams and tunnels, or use less and leave more in rivers for nature.

What it is

California gets most of its water in winter, when rain and snow fall; summers are dry. So the state catches water when it is wet and saves it for when it is dry. Some water sits in reservoirs -- lakes held back by dams -- and some is stored underground. Big canals and pumps move the water hundreds of miles to farms and cities. Farms use about 80% of the water the state develops for people (LAO). As droughts get worse, people argue about what to build next. One side wants more storage and bigger canals -- two examples are the planned Sites Reservoir and the Delta tunnel. The other side wants to waste less: they want to recycle more and leave more water in rivers for fish. Most experts say there is no single fix; California likely needs both smarter use and some new storage (PPIC). Here is where the facts lean: saving water and catching city stormwater usually costs less than building ocean-water plants, which remove salt from seawater (Pacific Institute). New reservoirs are 'expensive' and give 'only modest improvements in water supply' (Pacific Institute), though they do add real backup for dry years. California's rivers are also 'over-allocated' -- meaning more water is promised than nature can spare (Pacific Institute). So the real fight is about emphasis, not doing just one thing over the other.

How it works

California's water year swings between wet and dry. Much of the supply starts as mountain snow, which melts in spring and fills rivers and reservoirs. A key hub is the Sacramento-San Joaquin Delta, where two big rivers meet near San Francisco Bay -- giant state and federal projects pump water from the Delta and send it south to farms and cities. Water here is measured in 'acre-feet.' One acre-foot is about 326,000 gallons, roughly a year of water for a few households. Two big projects drive today's fight. Sites Reservoir would be an 'off-stream' reservoir, meaning it is filled by pumping water in during wet times rather than damming a main river; it could hold up to 1.5 million acre-feet. The other project is the Delta Conveyance Project, called the 'Delta tunnel.' It would move water under the Delta through a long tunnel, at an estimated cost near $20 billion. Why do people fight? Farms want water they can count on every year, cities want a safe backup for droughts and other emergencies, and fish and the Delta need water left in the rivers. Big projects cost billions, take many years, can harm nature, and someone has to pay. The split is mostly farms and rural areas against environmental and many urban groups, but it is not clean: some Southern California city agencies back the tunnel, while many Delta-area farmers and towns fight it. So the lines cross both party and rural-urban divides.

The debate — equal weight, both sides

The case for building more storage and supply

Most often made by farmers, water agencies, and many Central Valley and rural communities -- plus some large urban Southern California water suppliers. It crosses party lines.

When big storms hit, huge amounts of water rush to the sea unused. Storage catches that wet-year water for the dry years that always follow. Sites Reservoir, for instance, would hold 'enough to supply over 4.5 million homes for a year,' catching storm water for 'communities, farms, and the environment when water is more scarce.' Reliable water is not a luxury. California grows 'over a third of the country's vegetables and two-thirds of its fruits and nuts.' When water is cut, farmers leave fields empty, crops shrink, and food prices can rise across the nation. Storage keeps those deliveries steady. Cities need a safe backup too. Supporters say the Delta tunnel would add about half a million acre-feet a year -- 'enough to serve almost 5 million people.' Supporters also warn about earthquakes: a big quake could break the Delta's weak levees, the earth walls that hold back water, letting seawater into the supply. A tunnel, they argue, would guard city water if that happens. Storage can help nature too -- Sites is built to serve 'communities, farms, and the environment.' Climate change is making the swings wilder, with bigger floods and deeper droughts, so the state needs more places to hold wet-year water. Using less is smart, but a growing state cannot conserve its way through a dry year: you cannot save water you never caught.

The case for conservation and river flows

Most often made by environmental and fishing groups and many urban conservation advocates -- but also by Delta-area farmers and towns who oppose big export projects. It crosses party and rural-urban lines.

The cheapest new water is the water we don't waste. Using less costs far less than building big new supply. Catching city stormwater is cheap, running about $590 per acre-foot -- that's rain runoff caught from streets and roofs. Cleaning ocean water costs much more: these plants remove salt from seawater and run $2,100 or more (Pacific Institute). Big dams are a weaker deal. New reservoirs are 'expensive, politically controversial, and offer only modest improvements in water supply' (Pacific Institute). In plain words, you pay a lot and gain only a little, and the state's rivers are already 'over-allocated' (Pacific Institute) -- meaning more water is promised than nature can give. The Delta tunnel is a costly bet, and state lawmakers see cheaper paths. They point to 'far more affordable alternatives... including increasing water recycling and groundwater storage' (C-WIN). Using less is already helping. The state's cities and farms have been 'making strides' with water use (PPIC): recycling, better appliances, and smarter watering all add up, and catching stormwater helps too. Backers say these fixes are 'much better for the environment' than a giant tunnel (C-WIN). So spend on the cheapest, fastest fixes first.

Sources

Behind the summary

Cited by "The case for building more storage and supply"

Cited by "The case for conservation and river flows"

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