Knowing Delta’s past offers new ideas forward

Change in Delta land cover, early 1800s to early 2000s. Graphic by SFEI-ASC

By Alison Whipple
San Francisco Estuary Institute-Aquatic Science Center

Teetering atop a haystack to get his bearings, Sacramento County Surveyor Edwin Sherman observed “dense tules and willows” lining the sloughs that wove through “large tule plains and some grass.” The haystack also afforded him a dry bed at night when high tides inundated the surrounding wetlands of the Sacramento-San Joaquin Delta.

It was August 1859. Sherman was measuring the widths of the sloughs and noting the tidal patterns of the eastern Delta. He later recounted those details in a court case determining whether claimants to the Rancho Sanjon de los Moquelumnes Mexican land grant would retain title now that California was part of the United States.

Little did Sherman know that more than 150 years later his testimony and maps would help reveal what the Delta looked like and how it worked back then.

Scientists with the San Francisco Estuary Institute-Aquatic Science Center wanted to know. A clearer window into the past would help scientists, managers and policymakers envision a Delta of the future – one that would support native species and improve ecosystem function under climate change and continued changes in land and water use.

Alison Whipple examines historical maps at the California State Lands Commission in Sacramento, Aug. 19, 2009. Photo by Erin Beller/SFEI-ASC

In 2009, the Institute, with funding from the California Department of Fish and Game, began a collaborative effort to reconstruct in maps, text and graphics what had been the heart of the vast wetland system in the San Francisco Estuary and Central Valley. The resulting report on the historical ecology of the Sacramento-San Joaquin Delta was released Sept. 13. The research already has inspired collaboration on an “interactive map” of the historical Delta, between KQED-San Francisco’s science program “Quest,” Stanford University’s Bill Lane Center for the American West, and the Institute.

Getting to know a place as it was more than 160 years ago is daunting, but also incredibly rewarding. So much of the Delta’s native landscape has been erased or rearranged. Extensive reclamation of marshes for farming, massive water pumping, and upstream diversions to supply more than 25 million Californians and millions of acres of Central Valley farmland have profoundly affected the Delta’s native ecosystem. With only fragments of native habitat remaining, it is difficult to imagine how the pieces once fit together. Sherman would have a hard time recognizing the place, though 1,100 miles of levees would offer him many high and dry vantage points.

To reconstruct the pre-developed Delta of the early 1800s, the research team collected a wide variety of sources from more than 40 archives and institutions and numerous online databases. The team combed for clues in old navigational charts, government land surveys, hand-drawn maps, photos, diaries – you name it. No single source told the whole story. Together, the thousands of bits of evidence revealed Delta-wide landscape patterns and local details of a complex and productive ecosystem, compared with today’s largely homogenous and poorly functioning one.

Early Delta maps showed features such as forests along rivers where orchards now stand and vast lakes that today are only depressions. Aerial photos from the 1930s also provided pieces of the puzzle. Tonal signatures in the soil indicated former channels – waterways too small to be shown in early Delta maps.

Tidal marsh along the San Joaquin River, 1905. Photo by Grove Karl Gilbert/USGS

Hand-written and oral accounts often helped fill in the details of what the place was like on the ground. Worn and yellowed pages found in a state archive contained a hunter’s story of becoming lost one winter night around 1850. Hiking in the dark with dead ducks strung over his shoulders, he and his companion thrashed through “a vast wilderness of tules 10 to 15 feet in height.” They fell into numerous ponds, including one that “proved to be from 100 to 300 yards in width, as near as we could judge. The water was very cold and often waist-deep.”

As with the Sherman testimony, lawyers of the 1800s sometimes asked witnesses the same questions researchers today have about the past Delta: How deep is the water? What is the range of tides and how far do they extend? What is the width of that slough?

Patterns in the historical landscape began to emerge as one source led to another and accounts from travelers and surveyors clarified confusing features on maps. Using Geographic Information Systems software, the team synthesized the many pieces of information into a map of the early 1800s Delta habitat types.

One striking aspect of the map is the capillary-like networks of numerous tidal channels that dissipated into the wetlands. Most of those have been filled in, while the main sloughs and rivers delineating the Delta islands remain. Interestingly, the ratio of marsh to open water has essentially reversed, as only 3 percent of the historical wetland acreage exists today.

Overall, the report describes the extent, distribution and characteristics of historical habitat types – tidal wetlands, waterways, lakes and ponds, and riparian forest – within approximately 1,250 square miles of the Delta. It identifies three primary landscape types. The central Delta featured tidal freshwater wetlands of tule and willow with numerous winding channels. The north Delta was comprised of broad tule-filled flood basins rimmed with forested rivers and interspersed with lakes. And the south Delta contained perennial and seasonal wetlands with lakes, ponds, small channels, and riparian forest along the larger river branches.

The report and map do not present a blueprint for restoring the Delta that once was. Rather, they lay a foundation for understanding how the ecosystem once worked. Knowing what worked well for the native species is key to the Bay Delta Conservation Plan and other habitat restoration efforts underway today. It can help managers think about how individual restoration projects can add up to larger, functional landscapes.

In a follow-up investigation known as the Delta Landscapes Project, the Institute will link the historical landscape types – flood basin, riparian forest and such – to ecological functions and spotlight opportunities for supporting these relationships going forward. The multidisciplinary project team includes professors Peter Moyle, Jeff Mount and Jay Lund of the UC Davis Center for Watershed Sciences.

The Delta of the future will not look like it does today or as it did in the early 1800s. But knowing how the natural features once fit together will aid decisions about what elements might be desired in future landscapes.

Alison Whipple is lead author of the Delta report, Sacramento-San Joaquin Delta Historical Ecology Investigation: Exploring Pattern and Process. She joins the UC Davis Center for Watershed Sciences this fall as a doctoral student in hydrologic sciences.

References and further reading

Atwater BF, Conard SG, Dowden JN, et al. 1979. History, landforms, and vegetation of the estuary’s tidal marshes. In San Francisco Bay, the urbanized estuary: investigations into the natural history of San Francisco Bay and Delta with reference to the influence of man. Fifty-eighth annual meeting of the Pacific Division/American Association for the Advancement of Science held at San Francisco State University, San Francisco, California, June 12-16, 1977, ed. T. John Conomos, 493 p. San Francisco, Calif.: AAAS, Pacific Division.

California Department of Fish and Game. 2011. DRAFT Conservation Strategy for Restoration of the Sacramento-San Joaquin Delta Ecological Management Zone and the Sacramento and San Joaquin Valley Regions. Ecosystem Restoration Program.

Garone PF. 2011. The Fall and Rise of the Wetlands of California’s Great Central Valley. Berkeley and Los Angeles: University of California Press.

Greiner CM. 2010. Principles for Strategic Conservation and Restoration. Puget Sound Nearshore Ecosystem Restoration Project Report No. 2010-01. Published by the Washington Department of Fish and Wildlife, Olympia, Washington and the U.S. Army Corps of Engineers, Seattle, WA.

Grossinger RM. 2012. Napa Valley Historical Ecology Atlas: Exploring a Landscape of Transformation and Resilience. Berkeley, CA: University of California Press.

Grossinger RM. 2005. Documenting local landscape change: the San Francisco Bay area historical ecology project. In The Historical Ecology Handbook: A Restorationist’s Guide to Reference Ecosystems, ed. Dave Egan and Evelyn A. Howell, 425-442. Washington, DC: Island Press.

Hanak E, Lund J, Dinar A, Gray B, Howitt R, Mount JF, Moyle P, Thompson B. 2011. Managing California’s Water: From Conflict to Reconciliation. Public Policy Institute of California.

Hart, John. 2010. The Once and Future Delta: Mending the Broken Heart of California. Bay Nature.

Moyle PB, Lund JR, Bennett WA, et al. 2010. Habitat Variability and Complexity in the Upper San Francisco Estuary. San Francisco Estuary and Watershed Science 8(3):1-24.

Simenstad C, Reed D, Ford M. 2006. When is restoration not? Incorporating landscape-scale processes to restore self-sustaining ecosystems in coastal wetland restoration. Ecological Engineering 26:27-39.

Sommer L. 2012. California’s Deadlocked Delta: Can We Bring Back What We’ve Lost? KQED QUEST Northern California.

Sommer L, Whipple AA, McGhee G. 2012. Envisioning California’s Delta As it Was. KQED QUEST Northern California, San Francisco Estuary Institute-Aquatic Science Center, and the Bill Lane Center for the American West.

The Bay Institute (TBI). 1998. From the Sierra to the Sea: The Ecological History of the San Francisco Bay-Delta Watershed. The Bay Institute of San Francisco.

Thompson J. 1957. The Settlement Geography of the Sacramento-San Joaquin Delta, California. Geography, Stanford, CA.

Whipple AA, Grossinger RM, Rankin D, Stanford B, Askevold RA . 2012. Sacramento-San Joaquin Delta Historical Ecology Investigation: Exploring Pattern and Process. Prepared for the California Department of Fish and Game and Ecosystem Restoration Program. A Report of SFEI-ASC’s Historical Ecology Program, SFEI-ASC Publication #672, San Francisco Estuary Institute-Aquatic Science Center, Richmond, CA.

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