Challenges on modelling hydrodynamics in Bah

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Challenges on modelling hydrodynamics in Bahía
Blanca Estuary (Argentina)

• Francisco J Campuzano
• campuzanofj.maretec_at_ist.utl.pt
• www.ecomanage.info
• www.mohid.com
• www.ist.utl.pt

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Bahía Blanca Modelling

• Data made available
• Bathymetry with a 50 m resolution covering the
  inner part of the estuary
• Tides for three years at three stations.

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Bathymetric data provided
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Bahía Blanca Modelling

• Model History
• First attemp was to set only a model on the study
  area
• Bad results due that FES 95.2 predictions for the
  area did not match the observed values
• Boundary was taken further south to be able to
  simulate the amplification on the tidal wave

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Bahía Blanca Modelling

• Current State
• 2D model with three nesting levels
• Tides within the area are similar to the one
  predicted with the tidal components
• Rivers implemented (Sauche Chico River and
  Napostá Creek)

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Tidal Validation
retainer
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Tidal Data
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Simple Statistics
Puerto Ing. White Puerto Belgrano Torre Mareográfica
Number of values 26271 26102 24894
Sum 69235.51 64131.83 48232.98
Minimum -0.71 -0.81 -0.74
Maximum 5.56 5.79 4.6
Range 6.27 6.6 5.34
Mean 2.635 2.457 1.938
Median 2.89 2.63 2
First quartile 1.45 1.38 1.13
Third quartile 3.83 3.54 2.75
95 confidence interval 0.01605 0.01475 0.01167
99 confidence interval 0.0211 0.01939 0.01534
Variance 1.763 1.479 0.883
Average deviation 1.167 1.065 0.8137
Standard deviation 1.328 1.216 0.9397
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Tidal Component Speed (deg/hr) Puerto Ing. White Puerto Ing. White Puerto Belgrano Puerto Belgrano Torre Mareográfica Torre Mareográfica
Tidal Component Speed (deg/hr) Amplitude(cm) Phase (º) Amplitude(cm) Phase (º) Amplitude(cm) Phase (º)
ZO 0.000 263.544 0.000 245.635 0.000 193.273 0.000
M2 28.984 169.123 186.072 153.523 177.906 115.864 157.094
L2 29.528 25.475 255.364 22.471 245.987 15.977 220.692
N2 28.440 23.983 103.593 21.080 95.833 15.239 76.690
M4 57.968 22.764 178.277 16.141 184.234 6.396 171.968
S2 30.000 21.589 307.350 20.632 298.669 16.843 274.215
K1 15.041 21.151 61.178 21.481 54.527 20.345 45.066
O1 13.943 15.528 0.701 16.186 355.431 15.426 344.967
MU2 27.968 14.523 291.531 14.015 282.016 12.590 264.735
NU2 28.513 10.954 137.915 9.637 130.029 7.632 113.261
SA 0.041 9.897 24.659 15.510 305.984 11.841 311.449
S1 15.000 8.972 113.789 8.724 106.365 6.673 92.742
LAM2 29.456 8.951 233.328 7.942 223.408 6.163 199.674
MS4 58.984 7.253 311.277 5.593 307.499 2.372 269.579
MN4 57.424 7.188 98.079 5.176 105.629 2.174 92.423
K2 30.082 6.116 303.656 6.220 291.230 5.025 271.041
SK3 45.041 4.970 307.567 3.944 285.646 2.918 228.899
MK3 44.025 4.886 91.877 4.159 86.273 2.568 55.010
P1 14.959 4.555 34.857 4.454 26.892 4.703 23.217
MNS2 27.424 4.515 258.215 4.611 246.373 4.312 222.238
2N2 27.895 4.480 342.543 3.946 330.624 3.092 308.478
MA2 28.943 3.712 2.392 4.957 347.245 3.496 320.899
MB2 29.025 3.710 157.258 3.906 146.052 1.695 138.445
MSN2 30.544 3.521 171.699 3.066 160.906 1.859 137.340
MO3 42.927 3.238 26.334 2.209 22.867 0.689 341.457
Q1 13.399 2.924 339.006 2.946 330.851 2.820 320.335
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Analysis of the data

• Tidal amplitude increase towards the head of the
  estuary, with ranges higher within the estuary
  than the outer station
• Terms that explains the most of the tidal
  amplitude are mainly semidiurnal components (M2,
  L2, S2, L2, MU2), while can be appreciated also a
  influence from diurnal components (O1, K1) in
  addition as the tide moves to the inner part of
  the estuary the so-called compound tides
  generated by nonlinear interaction of primary
  constituent become increasingly important (M4,
  MS4, MN4).
• Increase of the mean water level (Z0) of 70 cm in
  the relative short distance between the most
  distanced stations ( 55Km)

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Mean Sea Level

• Moving average on the hourly data is performed
  with a period of 25, which correspond to twice
  the time of a semidiurnal tide, strong variations
  on the level water can be appreciated at all
  stations at the same time and with the similar
  magnitude

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Sea Level Pressure in Bahía Blanca region for the
period 2001-2004 (NCEP reanalysis data).
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Puerto Rosales monthly sea level records for the
period 1967-1971 (Permanent Service for Mean Sea
Level)
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25 hours moving average water level in IW (blue
line) and sea level pressure with a moving
average of 4 (24h) for the period January-May
2001
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Tidal data filtered
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Comments and Questions

• Rejecting all frequencies with signals under 8766
  h (365.24 days, SA, tidal component period), an
  annual pattern also appears on the tidal
  registry.
• When filtering with 365 days (8760 h), a better
  curve can be observed that is not explained by
  the presence of the SA component as its amplitude
  is 9.897 cm, when the signal observed on figure
  presents an amplitude of around 20 cm.
• Any suggestion to obtain better results and
  analysis on this?

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Model Forcing
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Comments and Questions

• Time ref used 0.0, son model used was the one
  with 0.005resolution, questions
• What is the time reference in such a big domain?
• What about reference level?

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Comments

• The three stations that were used to validate the
  results were not showing the increase in the mean
  sea level previously commented
• The model should be able to increase the mean
  level naturally as it was occurring in the
  reality.
• For testing this hypothesis, real values were
  imposed at the boundary of the son model to see
  how the tidal wave behaves on our bathymetry.

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Torre Mareográfica
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Puerto Belgrano
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Ingeniero White
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Challenges

• When using the nested models, how to set the
  reference and time level
• Respecting mean sea level there are annual
  oscillations that in my opinion are going to be
  complicated to simulate or include in the model,
  and then those short period oscillations that can
  modify extremely the tidal prism. An option could
  be to use the inverted barometer that Angela is
  developing, though no forecast could be done
  unless doing it operational. Or decide to move
  on, only with the astronomical tides.
• Are all these tidal gauges using the same level
  of reference? If yes, can we do something to
  increase the mean sea level (tried different
  manning with not much improvement, and it affects
  the shape of the tidal wave), if not, how can we
  decide which is the correct one (if any)?
• Include wind to see the effect on our model of
  the so-called sudestadas that tend to pile up
  waters in the estuary. Could this be partly
  responsible for the increase on the mean sea
  level?