Human Alterations to Estuaries:the San Francisco Bay-EstuaryA Case Study inManaging Estuarine EnvironmentsMARS 3450, 12 Nov 2013What is an Estuary? Textbook definition: ‘‘a semi-enclosed coastal body of water, which has a free connection with the open sea, and within which seawater is measurably diluted with freshwater derived from land drainage.” (Cameron and Pritchard, 1963) Sociological definition: The primary sites of human habitation on the coast because of transportation (shipping) and resources (food, fresh water).65 milesRiver InflowTreatedWastewaterHuman alterations to the San Francisco Bay Estuary1. Changes in freshwater flow2. Changes in physical environment3. Changes in water quality4. Changes in species assemblages5. Other types of disturbanceGeography of CaliforniaNorthern CaliforniaSouthern CaliforniaCentral CaliforniaWaterAgriculture/PopulationBig PopulationHistory of the State Water Project1963 - 73184919351945 1955http://www.publicaffairs.water.ca.gov/swp/history_swp.cfmWater to over 20 million peopleSWP Source WaterSacramento-San Joaquin Delta California Department of Water ResourcesClifton Court ForebayPumping station on SWPEverybody Is Happy!•No Floods•Plenty of Drinking Water•Cheap and Unlimited (?) Irrigation WaterBut Wait!There seems to be a Problem…Why is Everything Dying?1976-1977 DroughtWhy are Fish (and Shellfish) Populations Declining•Could it be due to overfishing?•Is it pollution?•Introduced species?•Is it the Clean Water Act?•Is it Climate Change?•Could the Water Projects be affecting the estuary?FreshwaterInflow• Quantity• Timing• QualityEstuarineConditions- Salinity- Transit time- Circulation- Dissolved & Particulate MaterialEstuarineResources- Species Composition, Abundance, Distribution- Primary and Secondary ProductionMerryl AlberLinked Ecosystem Processes in Estuaries Mean that Fisheries are Tied to FlowsParticles, larvae, etc retained in estuaryOutflow delivers larvae to seaInflow helps juveniles, spawners returnStratified Estuarine FlowHow do diversions affect an estuary?Water volume removedTiming of freshwater inflowsIntensity of freshwater inflow010203040506070195619591962196519681971197419771980198319861989199219951998200120042007Millions of Acre-FtDelta Outflow, 106acre-ftHistorical Delta Outflow into SFBDroughtEl NinoWater Year (Oct 1 - Sept 30)What is an acre-foot?A measurement used by water managersDerived from needs for farming and irrigationIt is the amount of water needed to cover 1 acre 1 foot deepNot a flow measurement - no time dimension (though 1 yr implied)1 acre = 43,560 sq ft (imagine a room 208.7 ft on a side)(the playing area (incl end zones) of a college football field is 1.32 acres1 acre-ft then is 43,560 sq ft x 1 ft deep = 43,560 cubic ftOr, 1 acre-ft = ~1,200 cubic meters~325 million gallons010203040506070195619591962196519681971197419771980198319861989199219951998200120042007Millions of Acre-FtDelta Outflow, 106acre-ftHistorical Delta Outflow into SFBDroughtEl NinoWater YearDrought: ~70% divertedWater volume removedOtherState Water ProjectCentral Valley ProjectConsumption within the DeltaLong-Term AverageFlow = 20.4 MAFMost of the rain comes in winterMost of the water is sold, at a substantially subsidized price, to irrigate crops. Water is needed in summerTiming of FlowsNormal hydrographOctober SeptemberJanuaryDiversion hydrographDiversion to StorageIrrigation runoff, mandated releasesHow does this affect the estuary?Effects on Estuary“Flushing Flows”Salinity DistributionCirculationFlushing FlowsTransit, or flushing time, is the average amount of time it takes river water to travel through an estuary.For a well-mixed estuary≈ River Flow Rate/Estuarine VolumeTransit/Flushing time varies with river flow,vigor of tidal mixingMerryl AlberMuch slower than for a stratified estuary at the same river flowFlushing time (d)Residence TimeWater gets “stale” at low flowsMerryl Alber100806550350The River Mile (kilometer) SystemOceanRiverDiversions affect the salinity distribution and physics of the estuaryDroughtUpstreamDownstreamGraph shows the position of the 2 psuisohaline. Effect of diversionsSalinity DistributionArthur et al 1976OceanRiverParticles, larvae, etc retained in estuaryInflow helps juveniles, spawners returnStratified Estuarine FlowSalinityLowHigh~2 psuStratification, estuarine circulation and particle retention (including fish larvae and food) are related to freshwater flow into an estuaryStratificationOceanRiverSalinity DistributionNormalized SalinityDistribution (X/X2)Optimum at an X/X2value of ~ 0.62 PSUManagement Tool!Arthur et al. 2006Habitat Matters, too1967-19761977-1992100806550350100Deep channel, swift flow, mostly downstream65Wide, shallow bay bordered by salt and fresh water marsh, good habitat35Wide, shallow bay, no cover50Deep channel, no marsh, strong tidal currentsHabitat quality and quantity varies with location1) There is a relationship between inflow and the position of the 2 PSU isohaline (X2) 2) There are relationships between X2 and many estuarine resources (phytoplankton, zooplankton, shrimp, shad, striped bass, herring, smelt, flounder, etc.) 3) Managers can regulate inflow to maintain X2 at a suitable location (but there are consequences!).4) Fish cost water (= money)Jassby et al. 1995NOTE: Exponential ScaleEstuarine Management by X2Inflow RequiredArthur et al. 2006Flow patterns can also be affectedNO diversionWITH diversionHuman alterations to SF Estuary1. Changes in freshwater flow2. Changes in physical environment3. Changes in water quality4. Changes in species assemblages5. Other types of disturbanceFrom Jaffe, Smith and Zink, USGScourtesy Dr. K. Grove, SFSUHuman activity affects sediment budgetsFrom Jaffe, Smith and Zink, USGS courtesy Dr. K. Grove, SFSU1856-1887Net sediment accumulationfrom hydraulic mining, poor land use practicesFrom Jaffe, Smith and Zink, USGS courtesy Dr. K. Grove, SFSU1951-1983Net sediment loss from erosion, dredging, compactionFrom Jaffe, Smith and Zink, USGScourtesy Dr. K. Grove, SFSUDecreasing turbidity is leading to higher chlorophyll concentrations, blooms of toxic algaeSan Francisco Estuary InstituteDiking and filling are also significant1770 - 1820 1985 - 1996Yet to Come:Sea Level RiseVulnerable to flooding with 1 meter of sea level riseThis area is already below sea levelHuman alterations to SF Estuary1. Changes in freshwater flow2. Changes in physical environment3. Changes in water