By James E. Cloern, Jane Kay, Wim Kimmerer, Jeffrey Mount, Peter B. Moyle and Anke Müeller-Solger

This essay is a condensed version of one that appeared in the journal San Francisco Estuary and Watershed Science (Vol. 15, Issue 2, Article 1), in July 2017.  The complete article with references and author’s contact information can be found at:

https://escholarship.org/uc/item/2d10g5vp

If we farmed the Central Valley or managed water supplies for San Francisco, San Jose, or Los Angeles, we might think that freshwater flowing from the Sacramento and San Joaquin Rivers through the Delta to San Francisco Bay is “wasted” because it ends up in the Pacific Ocean as an unused resource. However, different perspectives emerge as we follow the downstream movement of river water through the Delta and into San Francisco Bay.

If we were Delta farmers or administered Contra Costa County’s water supply, we would value how high flows reduce salt intrusion (Jassby et al. 1995) and protect water quality for drinking, growing crops, and meeting other customer needs.

If we were responsible for protecting at-risk species, we would value river water that flows through the Delta to the Bay and ocean because it stimulates migration and spawning of native Chinook salmon, Delta Smelt, Longfin Smelt, and Sacramento Splittail, while also reducing the potential for colonization and spread of non-native fishes (Brown et al. 2016). River flow reduces toxic selenium concentrations in clams eaten by sturgeon, splittail, and diving ducks (Stewart et al. 2013), and it delivers plankton and detritus to fuel production in downstream food webs (Sobczak et al. 2002).

If we managed a Bay Area storm water district or sewage treatment plant, we would value water that flows from the Delta into the Bay because it dilutes and flushes such urban pollutants as metals, microplastics, and nutrients (McCulloch et al. 1970).

If we directed restoration projects around the Bay, we would value water that flows from the Delta into the Bay because it brings sediment required to sustain marshes that otherwise would be lost to subsidence and sea level rise (Stralberg et al. 2011; Schoellhamer et al. 2016). Sediment supplies from rivers also sustain mudflats (Jaffe et al. 2007) used as habitat and probed for food by more than a million willets, sandpipers, dunlins, and other shorebirds during spring migration (Stenzel et al. 2002).

If we fished the Pacific for a living, we would value river flow into the Bay because it carries cues used by adult salmon to find their home streams and spawn (Dittman and Quinn 1996), it brings young salmon to the sea where they grow and mature, and it creates bottom currents that carry young English Sole, California Halibut, and Dungeness crabs into the Bay (Raimonet and Cloern 2016) where they feed and grow before returning to the ocean.

If we liked to romp along the shore or served on the California Coastal Commission, we would value rivers that flow to the sea because they supply the sand that keeps California’s beaches from eroding (Barnard et al. 2017).

Finally, if we were among those who want to conserve California’s landscape and biological diversity, we would value river water that flows to the sea because it creates one of the nation’s iconic estuaries, and sustains plant and animal communities found only where seawater and freshwater mix (Cloern et al. 2016).

Is the fresh river water that naturally flows through the Delta to San Francisco Bay and on to the Pacific Ocean “wasted?” No. The seaward flow of fresh water is essential to farmers, fishers, conservationists, seashore lovers, and government agencies that manage drinking water supplies, restore wetlands, protect coastlines, and clean up sewage and storm pollution. Wasted water to some is essential water to others.

Further Reading

Barnard PL, Hoover D, Hubbard DM, Snyder A, Ludka BC, Allan J, Kaminsky GM, Ruggiero P, Gallien TW, GabelL, McCandless D, Weiner HM, Cohn N, AndersonDL, Serafin KA. 2017. Extreme oceanographic forcing and coastal response due to the 2015-2016 El Niño. Nat Commun 8:14365. https://doi.org/10.1038/ncomms14365

Brown LR, Kimmerer W, Conrad JL, Lesmeister S, Müeller–Solger A. 2016. Food webs of the Delta, Suisun Bay, and Suisun Marsh: an update on current understanding and possibilities for management. San Franc Estuary Watershed Sci 14(3). https://doi.org/10.15447/sfews.2016v14iss3art4

Cloern JE, Barnard PL, Beller E, Callaway JC, GrenierJL, Grosholz ED, Grossinger R, Hieb K, Hollibaugh JT, Knowles N, Sutula M, Veloz S, Wasson K, Whipple A. Life on the edge—California’s estuaries. In: Mooney H, Zavaleta E, editors. 2016. Ecosystems of California: a source book. Oakland (CA): University of California Press. p 359-387.

Dittman A, Quinn T. Homing in Pacific salmon: mechanisms and ecological basis. J Exp Biol (1):83-91. https://doi.org/10.1242/jeb.199.1.83

Jaffe BE, Smith RE, Foxgrover AC. 2007. Anthropogenic influence on sedimentation and intertidal mudflat change in San Pablo Bay, California: 1856-1983. Estuar Coastal Shelf Sc 73:175-187. https://doi.org/10.1016/j.ecss.2007.02.017

Jassby AD, Kimmerer WJ, Monismith SG, Armor C, CloernJE, Powell TM, Schubel JR, Vendlinski TJ. 1995. Isohaline position as a habitat indicator for estuarine populations. Ecol Appl 5(1):272-289. https://doi.org/10.2307/1942069

McCulloch DS, Peterson DH, Carlson PR, Conomos TJ. 1970. Some effects of fresh-water inflow on the flushing of South San Francisco Bay—a preliminary report: U.S. Geological Survey Circular 637A. 27 p.

Raimonet M, Cloern JE. 2016. Estuary-ocean connectivity: fast physics and slow biology. Global Change Biology [Internet]. [cited 2017 March 18]. Available from: http://onlinelibrary.wiley.com/doi/10.1111/gcb.13546/full

Schoellhamer DH, Wright SA, Monismith SG, BergamaschiBA. 2016. Recent advances in understanding flow dynamics and transport of water-quality constituents in the Sacramento–San Joaquin River Delta. San Franc Estuary Watershed Sci 14(4). https://doi.org/10.15447/sfews.2016v14iss4art1

Sobczak W, Cloern J, Jassby A, Müeller-Solger A. 2002. Bioavailability of organic matter in a highly disturbed estuary: the role of detrital and algal resources. Proc National Acad Sci USA 99(12):8101-8105. https://doi.org/10.1073/pnas.122614399

Stralberg D, Brennan M, Callaway JC, Wood JK, SchileLM, Jongsomjit D, Kelly M, Parker VT, Crooks S. 2011. Evaluating tidal marsh sustainability in the face of sea-level rise: a hybrid modeling approach applied to San Francisco Bay. PloS one 6(11):e27388. https://doi.org/10.1371/journal.pone.0027388

Stenzel LE, Hickey CM, Kjelmyr JE, Page GW. 2002. Abundance and distribution of shorebirds in the San Francisco Bay area. Western Birds 33:69-98. Available from: https://www.westernfieldornithologists.org/archive/V33/33(2)%20p0069-p0098.pdf

Stewart AR, Luoma SN, Elrick KA, Carter JL, van der Wegen M. 2013. Influence of estuarine processes on spatiotemporal variation in bioavailable selenium. Mar Ecol Prog Ser 492:41-56. https://doi.org/10.3354/meps10503