The Central Valley and State Water Projects smooth out the dramatic seasonal swings in drainage across the 42 percent of California’s landscape that is the watershed of San Francisco Bay. These projects collect, store, and release fresh water so that it fills irrigation ditches and city faucets when needed. Before the projects were built, Central Valley inhabitants had a lot more water than they needed in winter. Flow gauges placed in the Sacramento River in the early 1900s confirmed that the river sometimes rose from its normal flow of 5,000 cubic feet per second (cfs) to 600,000 cfs in a matter of days--an amount that could never be contained within its natural banks. Even today, a train of storms can cause a very rapid rise in valley rivers; one former water manager remembers the reservoir coming up 16 feet in 24 hours. “You’ve got a kind of martini glass shape, so the lower the water level in the reservoir, the faster it can rise in a short period of time,” explains Holt.

The geography of the Central Valley is also unusually conducive to flooding. Its rivers drop quickly out of the mountains onto a vast flat basin, unlike the Mississippi River Valley, for example, whose waters gather and flow over half the continent. In his 1988 book Battling the Inland Sea, historian Robert Kelley described the scene before European settlement, after winter storms and spring snowmelt: “The Sacramento River and its tributaries rose like a vast taking in of breath to flow out over their banks onto the wide Valley floor, there to produce terrifying floods. On that remarkably level expanse the spreading waters then stilled and ponded to form an immense, quiet inland sea a hundred miles long. . . . Not until the late spring and summer months would it drain away downstream.”

Native Americans warned early settlers of the inland flooding, but the newcomers went ahead and built on the riverbanks anyway. Whereas the natives migrated between winter and summer villages to accommodate seasonal changes and collect different foods, the settlers weren’t so flexible. In the 1860s, the fledgling towns of Sacramento and Marysville spent months at a time underwater, and more than 80 years of ineffectual levee-building ensued.

Shasta Dam put a stop to such widespread flooding. But this year, the danger of any abundance of water is low. Listening to the chitchat on the streets of Redding, you hear talk of the size of the bathtub ring around the lake, and arguments about whether it looks worse or better than the droughts of ‘76 or ‘91. The ring is a pretty red color from the underlying sandstone, and a very rare plant called the Shasta snow wreath grows right above this sometimes wet, sometimes dry zone. The white-flowered shrub, like the salmon and everything else in California, will have to try to adapt to a new climate-changed hydrography in which snow melts sooner and rain comes later, and in which a higher dam may expand the bathtub ring into the shrub’s habitat. These are ecological challenges that more concrete may or may not be able to meet.

Ariel Rubissow Okamoto lives in San Francisco, writes on water issues, manages an organic vineyard, and is bringing up two daughters not to flush, not to run the tap while doing dishes, and to think of recycling not as an option, but as a way of life.