Lisa V. Lucas, James E. Cloern, Janet K. Thompson, and Nancy E. Monsen. 2002. Functional variability of habitats within the Sacramento–San Joaquin Delta: restoration implications. Ecological Applications 12:1528-1547.

Appendix A. Animations of numerical particle release in (1) the exterior channels north of Mildred Island, (2) the interior of Mildred Island, and (3) the exterior channels of Franks Tract.

(1) Exterior channels north of Mildred Island.

What you are seeing:

During flood tide (water and particles flow to the south), many particles are carried into Mildred Island (MI), a tidal lake in the Sacramento–San Joaquin River Delta. During the following ebb tide (water and particles flow to the north), the majority of these particles are transported back into the northeast or northwest channel. Tidal sloshing continues during subsequent tidal cycles, and the particle cloud disperses considerably over time.

Key points:

• Tidal interaction of northern MI with adjacent channel is significant.
• Tidally averaged import of northern channel water and particles into MI may be substantial.
• These processes help explain the observed North–South chl a gradient and tidal variations in chl a spatial patterns.

run animation (mi_exterior.mpg)  

(NOTE: If the movie image appears out of focus, please adjust the width of your movie viewer window or set your viewer preferences to not resize the image.)

Details of the simulation:

• June 1999 hydrology during a spring tide.
• Numerical particles released on 17 June 1999 at 2:00 PST.
• Simulation shows time-varying particle locations over 120 hours.
• Hydrodynamics simulated using Delta TRIM model (Casulli and Cattani 1994, Monsen 2001).
• Particle trajectories determined by a linear interpolation of the velocity field.

(2) Numerical drogue release in the interior of Mildred Island.

What you are seeing:

Numerical particles are initialized uniformly inside Mildred Island (MI), a tidal lake in the Sacramento–San Joaquin River Delta. Water mass and particles in MI exchange with the southern channel, as channel-to-lake transport during ebb tide (water and particles moving north) and lake-to-channel transport during flood (water and particles moving south).

Because the southern opening is smaller and shallower than the NE opening, the rates of mass and momentum exchange with the southern channel are less than with the northern channel. As a result, particle flushing is more efficient in northern MI, and a spatial gradient in particle density (increasing to the south) develops.

Particle tidal excursion (an indicator of dispersion and flushing) generally decreases southward and appears to reach a minimum in the SE portion of MI, probably due to the isolation of that region from significant levee breaks.

Key point of animation:

• Residence time is spatially heterogeneous within MI, increasing southward. This partially explains the North–South chl a gradient observed in MI.

run animation (mi_interior.mpg)

(NOTE: If the movie image appears out of focus, please adjust the width of your movie viewer window or set your viewer preferences to not resize the image.)

Details of the simulation:

• June 1999 hydrology during a spring tide.
• Numerical particles released on 17 June 1999 at 8:00  PST.
• Simulation shows time-varying particle locations over 120 hours.
• Hydrodynamics simulated using Delta TRIM model (Casulli and Cattani 1994, Monsen 2001).
• Particle trajectories determined by a linear interpolation of the velocity field.

(3) Exterior eastern channels of Franks Tract.

What you are seeing:

During ebb tide (water and particles flow to the west), the majority of the particles enter Franks Tract (FT), a tidal lake in the Sacramento–San Joaquin River Delta, some traversing almost one-third the distance of FT. During flood tide (water and particles flow to the east), many particles return to the channels while others remain in the eastern portion of FT. After several tide cycles, channel initiated particles have infiltrated the eastern half of FT, representing long-term net transport into FT.

Key points of the animation:

• Tidal sloshing between lake interior and adjacent channels is significant.
• Tidally averaged import of channel water into FT can be substantial. This may explain how phytoplankton biomass was sustained in FT, where net phytoplankton growth rate was negative.
• The combination of tides and multiple levee breaks results in substantial tidal dispersion. This explains the weaker spatial gradients in FT than in Mildred Island and stronger gradients on neap tide compared to spring tide.

run animation (frank_exterior.mpg)

(NOTE: If the movie image appears out of focus, please adjust the width of your movie viewer window or set your viewer preferences to not resize the image.)

Details of the simulation:

• June 1999 hydrology during a spring tide.
• Numerical particles released on 18 June 1999 at 7:00 PST.
• Simulation shows time-varying particle locations over 72 hours.
• Hydrodynamics simulated using Delta TRIM model (Casulli and Cattani 1994, Monsen 2001).
• Particle trajectories determined by a linear interpolation of the velocity field

Literature cited

Casulli, V., and E. Cattani. 1994. Stability, accuracy and efficiency of a semi-implicit method for three-dimensional shallow water flow. Computers and Mathematics with Applications 27:99-112.

Monsen, N. 2001. A study of subtidal transport in Suisun Bay and the Sacramento–San Joaquin Delta, California. Ph.D. Thesis, Stanford University, Stanford, California, USA.