assessment of long-term impacts due to sediment supply changes towards san francisco bay-delta

Assessment of long-term impacts due to sediment supply changes towards San Francisco Bay-Delta Fernanda M. Achete - UNESCO-IHE - [email protected] Mick van der Wegen - UNESCO-IHE - [email protected] Bruce E. Jaffe - U.S.G.S, Pacific Coastal and Marine Science Center, Santa Cruz - [email protected] NUMERICAL MODEL • D-Flow FM • Flexible mesh • Process-based model • 2D • Hydrodynamics • Delft WAQ (Water Quality) • Offline Coupling • Sediment Suspension Concentration (SSC) • Deposition • Two mud fractions 35% 15% 50% Dflow-FM Boundary Conditions 0 50 100 150 200 250 300 350 400 0 500 1000 1500 2000 2500 3000 D ays V olum e[m 3/s] S acram ento P um ping*(-1) INTRODUCTION The main source of sediment to San Francisco Bay is the Sacramento San-Joaquin Delta. The objective of this poster is to assess sediment trapping in the Delta and the influences of river discharge and pumping on trapping. • The Delta works as a trap for sediment coming from the Sacramento and San Joaquin Rivers • ~70% of the sediment stays in the Delta (no pumping), increasing to ~ 80% with pumping • This trend correlates with pumping vs. non-pumping changes in Delta in/outflow RESULTS • Sacramento River contribution to the bottom sediment composition varies spatially due to discharge. Higher Sacramento River flows result in sediment depositing further south. • Q black < Qgreen < Qred • The decrease in Sacramento River sediment flux at the inland and bay sides of the Delta is greater than 1 order of magnitude. • Lower discharge results in a larger trapping efficiency • The highest sedimentation observed in the Delta is located in the breached island • Varying discharge results in the same sedimentation pattern but different layer thicknesses DISCUSSION POINTS How much does the grain size influence dynamics? How applicable are these results to other estuaries? Kimmerer, 2004 0 60 120 180 240 300 360 10 2 10 3 10 4 10 5 10 6 10 7 10 8 D ays C um ulative S edim entFlux [g] Low D ischarge-Inflow Low Discharge-O utflow High D ischarge-Inflow High Discharge-O utflow D ry S eason W etS eason Anomaly map of total Sediment in S1 Total Sediment in S1 12.7x10 6 g 12.7x10 6 g 4.6x10 6 g 4.6x1 0 6 g 4.2x10 6 g 2.8x1 0 6 g Sacramento River and Pumping Inflo w Inflo w Outflo w [g] No Pumpin g Pumpin g

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Assessment of long-term impacts due to sediment supply changes towards San Francisco Bay-Delta. 15%. Fernanda M. Achete - UNESCO-IHE - [email protected] Mick van der Wegen - UNESCO-IHE - [email protected] - PowerPoint PPT Presentation

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Assessment of long-term impacts due to sediment supply changes towardsSan Francisco Bay-Delta

Fernanda M. Achete - UNESCO-IHE - [email protected] Mick van der Wegen - UNESCO-IHE - [email protected]

Bruce E. Jaffe - U.S.G.S, Pacific Coastal and Marine Science Center, Santa Cruz - [email protected]

NUMERICAL MODEL •D-Flow FM

•Flexible mesh•Process-based model•2D•Hydrodynamics

•Delft WAQ (Water Quality)•Offline Coupling •Sediment Suspension Concentration (SSC)•Deposition•Two mud fractions

35%

15%

50%

Dflow-FM

Boundary Conditions

0 50 100 150 200 250 300 350 4000

500

1000

1500

2000

2500

3000

Days

Vol

ume[

m3/

SacramentoPumping*(-1)

INTRODUCTIONThe main source of sediment to San Francisco Bay is the Sacramento San-Joaquin Delta. The objective of this poster is to assess sediment trapping in the Delta and the influences of river discharge and pumping on trapping.

• The Delta works as a trap for sediment coming from the Sacramento and San Joaquin Rivers

• ~70% of the sediment stays in the Delta (no pumping), increasing to ~ 80% with pumping

• This trend correlates with pumping vs. non-pumping changes in Delta in/outflow

RESULTS

• Sacramento River contribution to the bottom sediment composition varies spatially due to discharge. Higher Sacramento River flows result in sediment depositing further south.

• Q black < Qgreen < Qred

•The decrease in Sacramento River sediment flux at the inland and bay sides of the Delta is greater than 1 order of magnitude.

•Lower discharge results in a larger trapping efficiency

• The highest sedimentation observed in the Delta is located in the breached island

• Varying discharge results in the same sedimentation pattern but different layer thicknesses

DISCUSSION POINTSHow much does the grain size influence dynamics?How applicable are these results to other estuaries?

Kimmerer, 2004

0 60 120 180 240 300 36010

103

104

105

106