An explanatory series focusing on one of the most complex issues facing California: water sharing. And at its core is the Sacramento-San Joaquin Bay Delta. Stay with kcet.org/baydelta for all the project's stories.
When rising sea levels created the Sacramento-San Joaquin Delta about 6,000 years ago, they made a place unlike any on earth. The prehistoric Delta was a thousand square miles of wetlands, fed by snowmelt and rain from some of the tallest mountains in North America, and influenced by tides despite its location 60 miles from the closest ocean.
The prehistoric Delta was almost unimaginably fertile. The abundant wetland vegetation created rich peat soil as it decayed, with topsoil going down as deep as 60 feet. A network of rivers brought minerals down from the High Sierra, the Cascades, the Klamath Mountains. In the Delta, those essential plant nutrients would intermingle with those from deep ocean upwellings, brought into the interior by the cycling of the tides.
The result was as biologically diverse a landscape as existed in California, a richness of life almost incomprehensible to present-day Californians.
Take a look at images of the Okavango Delta in the Kalahari Desert, where antelope and elephants and hippos wander in seasonally flooded grasslands, and you'll have a fair rough approximation of what California's Delta used to look like -- as long as you swap grizzly bears for elephants and elk for hippos.
From the present-day location of Knights Landing just upstream of Sacramento, to the spot where the now-tamed Tuolumne and Stanislaus rivers flow into the San Joaquin near Modesto, the Delta was a diverse, rich network of complex and ever-shifting watercourses, pools and flood plains.
The Delta's astonishing richness stemmed in part from the fact that it was hemmed in. Unlike most other river deltas, which spread sediment from their rivers out into the ocean in a broad fan, California's Delta is an inland river delta contained behind a mountain range, the Coast Ranges, with only a narrow outlet to the San Francisco Bay and the Pacific.
There are a few other inland river deltas in the world, such as Botswana's Okavango and the Peace-Athabasca Delta in Alberta, where rivers flow out into broad valleys and spread out over the landscape. But unlike almost all those other inland deltas, the delta of the Sacramento and San Joaquin has a sea-level connection to the ocean. That means tides influence the Delta. It also means the Delta is home to ocean-going anadromous fish, which contribute to the general abundance of the local food chain.
When Spanish priest Pedro Font climbed a hill near Suisun Bay in 1776 and looked out over the Delta, he described it as "immeasurable." Before him, he wrote, was a huge, nearly treeless plain full of shining water, verdant islands covered in the six-foot freshwater bulrushes called tules, all of the land before him teeming with wildlife. His party spent the next several days trying to make headway across that plain, getting tangled in tules, lost in a maze of channels, and -- at last -- confronted by local Native people, who had heard of the Spaniards, their missions, and the enslaved Native labor that supported them. Fortunately for Font, those Natives decided to let the party go.
That Delta may have seemed "immeasurable," but it wasn't featureless. There were variations in the nature of the Delta's landscape over broad areas. The Central Delta, which Font watched from his vantage point near present-day Antioch, was a plain of tidal wetlands, open water, and peat islands protected by natural, river-deposited levees. To the north, toward today's Sacramento, were vast flood basins, grasslands that would flood in spring, when snowmelt runoff hit the Sacramento and its tributaries overtopped those rivers' forested natural levees. The submerged grasses in those flood basins provided important nursery habitat for the valley's gigantic runs of salmon. South of the Central Delta, the San Joaquin split into three main branches -- "distributaries" in hydrological jargon -- that flowed across a vernal pool-studded floodplain that slowly merged with the Central Delta's tidal wetlands.
This diverse landscape was inhabited by a diverse group of Native people, with at least 20 thriving communities of people -- speaking a wealth of languages from four major linguistic groups -- subsisting on the land's abundant shellfish, fish, game, and seeds and edible bulbs.
The Delta wasn't a wilderness. People used the whole landscape, burned areas to promote grass seed harvests, built villages along many of the region's permanent watercourses, fished the delta's sloughs with nets. Accounts written in the late 1830s describe Native villages whose nearby streambanks were carpeted with mussel shells, and single scoops of the soft tidal mud bringing up as many as a dozen clams.
Though descendants of the Delta's Native people are very much alive, Native landscape management of the Delta largely ended in the 1830s. Subject to new diseases and Forced relocation to the missions along the coast, the Delta's people were nearly wiped out by an 1833 malaria epidemic that killed an estimated 75 percent of the local population.
It's generally assumed that malaria was inadvertently introduced to the Delta, and the rest of the Central Valley, by trappers working for the Hudson's Bay Company. Trappers seeking pelts from the Delta's abundant beaver and river otter populations showed up in 1826.
Beavers in particular were so thoroughly trapped out of the state of California by the 1840s that many later biologists regarded the aquatic rodents as non-native. But the Delta's tortuous maze of sloughs and channels provided a refuge of sorts. Though beaver numbers in the Delta were indeed decimated, enough escaped to repopulate much of the rest of the state within the next 150 years.
Decimating the Delta's beaver population might well have had as much of a long-term effect on the landscape as the removal of Native people. Among the many different kinds of watercourses found in the Delta were so-called "beaver cuts," 18-inch wide canals that the beavers carved as pathways from one patch of open water to another, or inland toward sources of food. These shallow canals, which were abundant throughout the Delta, may have provided important shelter for smaller fish and other aquatic animals. They almost certainly provided other wildlife species with access to otherwise landlocked ponds and small lakes.
Where there was water, there were waterfowl, and the Delta had a lot of them. Conservative estimates put the Delta's seasonal population of migrating ducks, geese, and other waterbirds at 10 million or more. That would make the Delta some of the most valuable stopover habitat on the Pacific Flyway, even back in the days when that migration path still included the now-extinct Tulare Lake and a functioning Colorado River Delta.
These millions of waterfowl, traveling in flocks miles long that darkened the sky as they passed, weren't just picturesque: they too reshaped and molded the Delta's landscape. When migrating Canada geese land on a stretch of open water, they usually set to work eating any edible vegetation at hand. Imagine a flock of 500,000 wintering Canada geese landing on a couple square miles of open water in the prehistoric Delta. When they moved on, that pond would have a lot less emergent vegetation than it used to. It would also have a lot more goose poop in the water, a nutrient boon for aquatic plants and bottom-dwelling animals.
The Delta's waterfowl diversity included Canada and snow geese, dozens of species of duck, trumpeter swans, egrets, herons, and cranes, white pelicans, and others. Though the Delta and the connected wetlands that run up and down the center of the Central Valley can still attract impressive flocks of waterfowl, many of the species once abundant in the Delta have seen better days. Trumpeter swans, North America's heaviest waterfowl species, suffered greatly from hunting for the millinery trade, and are now essentially gone from the Delta -- though occasional sightings do bring birders out to the Valley's other wetlands.
Waterfowl weren't the only Delta birds described as "darkening the sky" when they took flight. The Delta was also habitat for a very large number of perching birds, which took advantage of the landscape's wealth of habitat types from willow bosques to tule marshes. The tricolored blackbird, once considered California's most common bird species, congregated in huge breeding colonies in floodplain grasslands and riparian forests, and was especially common in the Delta. Many, many millions of tricolored blackbirds lived in the prehistoric Delta, though their numbers collapsed as more and more of their habitat was converted to agricultural use by settlers. Today, perhaps 145,000 birds remain of the tens of millions that winged around the state two centuries ago.
And of course, there were quite a few mammals of considerable size in the prehistoric Delta. We'll describe those in part two of this piece.