Lund, Jay

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Article, Published VersionLund, JaySan Francisco Bay-Delta: Ground Zero for california waterchallenges - risks and water resourcesHydrolinkVerfügbar unter/Available at: https://hdl.handle.net/20.500.11970/109274Vorgeschlagene Zitierweise/Suggested citation:Lund, Jay (2015): San Francisco Bay-Delta: Ground Zero for california water challenges -risks and water resources. In: Hydrolink 2015/1. Madrid: International Association for Hydro-Environment Engineering and Research (IAHR). S. 6-7. https://iahr.oss-accelerate.aliyuncs.com/library/HydroLink/HydroLink2015_01_Sacramento_San_Joaquin_River_Delta.pdf.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.6 hydrolink number 1/2015Coastal deltas are frequently changing andshifting landscapes subject to varying fresh-water and sediment flows, sea level changesand tides, as well as many forms of human landand water management. California’sSacramento-San Joaquin Delta shares theinherent instability of delta landscapes, and alsoserves a central role in the water supply for oneof the world’s largest economies. It is asubstantial agricultural area, and has thegreatest potential for restored aquatic habitat ofany region in California. However, as summarized in Table 1, thisCalifornia Delta, part of the largest estuary onthe Americas’ Pacific coast, is particularlyunstable in serving these purposes due toCalifornia’s highly variable hydrology, intenseand changing human management of waterand land, invasive species, climate change, andthe threat of major earthquakes.  Many of these changes are inevitable, andthreaten several current functions of California’sDelta, with implications for management and forhydrologists and water managers in similarsituations worldwide.Risks to Landforms in the DeltaA fundamental risk to the Sacramento-SanJoaquin Delta is to its current landforms. Landsubsidence is a common problem for thestability of developed delta lands worldwide,about $150 million annually, and lost economicvalue added of about $83 million/year. Thiseconomic harm would be partially mitigated bythe expected expansion of some recreationalfishing and boating activities. Internal seepage isanother growing problem for some of the mostsubsided islands, as waterlogging slowlydisplaces productive agricultural acreage withsubsided and disconnected wetlands.  Risks to water supplies from theDeltaThe Delta directly or indirectly supplies water tomost of California’s population and much of itsirrigated agriculture. Landform, water quality,water management, and ecological changescan affect both the ability to pump water directlyfrom the Delta and the ability to divert water fromupstream tributaries.  Major flooding of one or more Delta islandsduring California’s long dry season, due to amajor earthquake for example, could lead tosevere sea water intrusions, and so jeopardizewater quality for users of Delta. Lack of largefreshwater inflows into the southern Delta, wheremost water export pumps are located, couldprolong this salinity intrusion for many months.  However, permanent flooding of islands oftentends to dampen local tidal ranges and mixing,which reduces seawater intrusion into the Deltaat high tides. However, Delta island levee failuresalso would expose more Delta water to contami-nants from peat soils, adding treatment costs forurban water users.Continued tightening of drinking water qualitystandards is making treatment of Delta watermore expensive, due to its high organic carboncontent, along with salts and bromides fromseawater and agricultural drainage. Rising saltconcentrations in Delta water also affect localagriculture and larger agricultural areasdepending on water exports pumped from theDelta.  Risks to EcosystemsThe Delta is the permanent or seasonal home toseveral endangered species of fish and otherSAN FRANCISCO BAY-DELTA:GROUND ZERO FOR CALIFORNIA WATER CHALLENGES - RISKS AND WATER RESOURCESBY JAY LUNDDriverSea level rise l l l l l lLand subsidence l l lFloods l l lEarthquakes l l l l lUpstream sediment & quality l l l lTightening treatment standards l lWater exports l l l lEndangered & invasive species l l l lLandformsIsland floodingSalinity intrusionWater suppliesNative fish speciesRecreational fishingLocal economy & societyChange  ⁄from the Netherlands to Louisiana. Since havingbeen largely diked and drained, starting in the1860s, the California Delta’s western and centralpeat lands have been exposed to air, oxidized,and subsided, often at the rate of severalcentimeters per year. Many of the mostsubsided islands are now 3-9 meters below sealevel, as seen in Figure 1.  This raises flooding and drainage issues in themost subsided lands. This fundamental insta-bility in the landscape from land subsidence isexacerbated with rising sea levels, threat ofearthquakes, floods, climate change, and lowagricultural land values for most deeplysubsided lands. In the last 4 decades, 5 of 40subsided Delta islands have been flooded, withfour of these flooded islands having beenabandoned.  Newly flooded islands and other drivers ofchange often have fundamental implications forCalifornia’s water supply system, the region’snative and recreational ecosystems, and theDelta’s local society and economy.Risks to Local Society and EconomyThe flooding of Delta islands will affect humanuses of the Delta. Up to about 31,000 hectaresof subsided, mostly agricultural land are at riskof abandonment following levee failure. Thiswould result in the loss of about 1,000 directand indirect jobs, gross crop revenue losses ofTable 1 - Major drivers of change and their impacts for California’s Sacramento-San Joaquin Delta  Themed issue Sacramento – San Joaquin River Delta7hydrolink number 1/2015concerns, have led to great, but highly contro-versial, interest in the construction of tunnels todivert fresh water from the Sacramento Riverunder the Delta to the major water diversionlocations for cities and farms south and west ofthe Delta.For ecosystems, there is great interest inrestoring the Delta’s tidal wetlands, which arelimited by the scarcity of suitable land elevationsafter subsidence, changing and reducing waterdiversions, and controlling the introduction ofnew invasive species. These actions wouldaffect local and regional economic activity,displace some agriculture, and would usuallyreduce water diversions from the Delta. Thisreduction in Delta water exports would result inseveral hundred million dollars per year of losteconomic value, especially during drier years.Much of the Delta’s local economy and societywill be unaffected by these changes because itlies far from areas of the Delta likely to be mostanimals and has become home to an increasingnumber of invasive and introduced species. Inmuch of the Delta, native fish species are only10-20% of total fish biomass. Invasive clams,zooplankton, and plants have fundamentallyaltered most of the Delta’s ecosystem. TheDelta’s landscape has changed from predomi-nantly tidal freshwater wetlands to often-subsided agricultural land ringed by riprappedlevees. Stream and channel flows have beengreatly altered in their flow patterns and directiondue to upstream water management and in-Delta pumping. Flooding of Delta islands would return someareas to open water, enlarging aquatic habitatarea, but at much greater depths, quite differentfrom the vast freshwater tidal marshes of pre-development times.  Uncertain solutionsThese changes, and tightening restrictions onwater diversions due to endangered speciesIAHRJay Lund is the Director, Center for Water-shed Sciences, and Ray B. Krone Professorof Environmental Engineering, University ofCalifornia, Davis, California. Dr. Lund’s research and teaching interests focus onapplying systems analysis and economicmethods to infrastructure and environmen-tal problems, including policy, planning,and management studies. His work is primarily in water resources and environ-mental system engineering. He is the chair-elect of the Independent Science Board ofthe Delta Stewardship Council, California. Above sea levelSea level to 10 feet below sea level10 to 15 feet below sea level15 feet or more below sea levelLand Subsidence in the DeltaSOURCE:  Department of Water Resources (1995).LodiStocktonSacramentoClarksburgFreeportHoodCourtlandWalnutGroveIsletonRio VistaFairfieldConcordAntioch OakleyPittsburgDiscoveryBayLos VaquerosReservoirSuisun MarshSalinity ControlGateBarker SloughPumping PlantYOLO BYPASSTracyMantecaLathropHarvey O. BanksDelta Pumping PlantSouth BayPumping PlantTracyPumpingPlantRydeCOSUMNES R. GrizzlyBaySuisun BaySACRAMENTO R.MOKELUMNE  R.Dry CreekContra Costa CanalMarsh CreekLindsey SloughCache SloughCarquinezStraitHonkerBayDelta-Mendota CanalCalifornia AqueductAMERICAN R.SuisunMarshSuisun MarshSAN JOAQUIN R.N2 0 2 4 6milesaffected. However, these changes will funda-mentally affect much of the western and centralsubsided areas of the Delta, and there is greatinterest in further strengthening Delta levees andincreasing freshwater flushing flows from theDelta.Several State and federal agencies and majorDelta export water users are currently proposinga Bay Delta Conservation Plan that wouldrestore extensive habitat areas, build tunnels toimprove Delta water export quality and reliability,and provide a different long-term basis formanaging water in the Delta. This plan is unsur-prisingly controversial.As with many deltas around the world, somechanges are physically and economicallyinevitable for California’s Sacramento-SanJoaquin Delta. Changes are always difficult withso many diverse interests in the outcomes andmanagement of change. California faces astrategic challenge in how to best manage theDelta, this central feature of local and statewidewater supply and ecosystem importance. Timewill tell how successful California will be in thiseffort, given the highly decentralized, and locallyeffective, system of water governance inCalifornia.ReferencesHealey, M. (ed.), The State of Bay-Delta Science 2008, Delta ScienceProgram, Delta Stewardship Council, Sacramento, CA, 2008.Lund, J., E. Hanak, W. Fleenor, W. Bennett, R. Howitt, J. Mount, and P.Moyle, Comparing Futures for the Sacramento-San Joaquin Delta,University of California Press, Berkeley, CA, February 2010.Medellín-Azuara, J., E. Hanak, R. Howitt, and J. Lund, Transitions forthe Delta Economy, Public Policy Institute of California, SanFrancisco, CA, 62 pp., 2012.Figure 1 - Land subsidence in California’s Sacramento-San Joaquin Delta

San Francisco Bay-Delta: Ground Zero for california water challenges - risks and water resources

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San Francisco Bay-Delta: Ground Zero for california water challenges - risks and water resources

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