Final Project

Summary of Results &

Conclusions

Layer 1

Hydraulic Conductivity

PW2 discharge reducedTo 0.90E8 ft3/year

2008Project“ TRUTH”

Layer 2

Layer 3

All these complicated details may not matter.

What matters is to capture the essential featuresof the system for the purposes of predictingthe response to pumping and the movementof the contaminant particles.

Extinction depths = 10, 30 ft

Leakance = 4 ft/yr

Recharge rates

PW2. Dry cell.

Reduce pumping rate from-0.99E8 ft3/yearto -0.90E8 ft3/year

PW1 doesn’t captureany particles.

PW1

No cone of depression.PW1 doesn’t look like a sinkand doesn’t capture particles.

PW 2

All the particles exit in wells;none end up in the playa.

Particles by-pass PW1 andexit in PW2.

All of the particles that enter in layer 1,stay in layer 1.

Calibration Prediction

Group ARM h ARM ET (x10e7)

ARM h (at targets)

1 0.72 0.58 8.51

2 0.97 1.19 10.37

3 0.93 0.74 6.12

4* 0.93 2.76 6.84

Predicted ARM > Calibrated ARM

*Dry cells. PW2 went dry.

Calibration Prediction

Group ARM h ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)**

1 0.72 0.58 8.51 26.64

2 0.97 1.19 10.37 18.72

3 0.93 0.74 6.12 3.57

4* 0.93 2.76 6.84 6.50

1. Predicted ARM > Calibrated ARM

2. Generally predicted ARM at non-target cells > predicted ARM at target cells

*Dry cells. PW2 went dry. ** Doesn’t include PW2since it is also a target.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.5 1 1.5 2 2.5 3

Calibrated ARMP

red

icte

d A

RM

-ta

rge

ts

0

2

4

6

8

10

12

14

0 0.5 1 1.5 2 2.5 3

Calibrated ARM

Pre

dic

ted

AR

M-p

um

pin

g w

ells

Includes results from2006 and 4 other years

724 Project Results

A “good” calibrationdoes not guarantee

an accurate prediction.

?

Calibration Prediction

Group ARM h

ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)*

1 1.16 0.20 2.87 5.02

2 0.80 0.52 1.81 2.27

3 1.18 0.47 2.73 12.77

4 2.39 0.784 0.80 0.76

5 2.07 1.13 1.61 2.61

6 0.96 0.45 2.13 2.90

7 0.92 0.956 1.18 0.92

8 0.50 0.604 3.70 2.71

9 0.054 0.0049 3.54 5.52

1. Predicted ARM > Calibrated ARM

2. Predicted ARM at pumping wells > predicted ARM at targets

Calibrated ARM of around 1.0 is a good calibration.

2006Project Results

*Does not include PW2 since it is also a target.

Calibration Prediction

Group

ARM h

ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)*

1 1.16 0.20 2.87 5.02

2 0.80 0.52 1.81 2.27

3 1.18 0.47 2.73 12.77

4 2.39 0.784 0.80 0.76

5 2.07 1.13 1.61 2.61

6 0.96 0.45 2.13 2.90

7 0.92 0.96 1.18 0.92

8 0.50 0.60 3.70 2.71

9 0.054 0.0049 3.54 5.52

Calibrated ARM of around 1.0 is a good calibration.

Predicted ARM at targets > predicted ARM at pumping wells

1. Predicted ARM > Calibrated ARM

2. Predicted ARM at pumping wells > predicted ARM at targets

Calibration Prediction

Group ARM h

ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)*

1 1.16 0.20 2.87 5.02

2 0.8 0.52 1.81 2.27

3 1.18 0.47 2.73 12.77

4 2.39 0.78 0.80 0.76

5 2.07 1.10 1.61 2.61

6 0.96 0.48 2.13 2.90

7 0.92 0.96 1.18 0.92

8 0.50 0.60 3.70 2.71

9 0.054 0.0049 3.54 5.52

2006Project Results

Despite the relativelypoor calibration, groups4 and 5 managed tocapture the essentialfeatures of the systemfor the purpose of the prediction.

Calibration Prediction

Group ARM h ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)**

1 0.72 0.58 8.51 26.64

2 0.97 1.19 10.37 18.72

3 0.93 0.74 6.12 3.57

4* 0.93 2.76 6.84 6.50

*Dry cells. PW2 went dry. ** Doesn’t include PW2since it is also a target.

2008 Results

2008 Particle Tracking

Group P1 P2 P3 P4 P5 P6 P7

1 4507PW2

2100 PW2

461,423 PW2

220 PW4

3956 playa

24,923PW2

1395 PW2

2 719PW2

253 PW2

2192 PW2

86PW4

5874 PW2

540PW2

2424PW2

3 87,800PW2

114,000 PW2

646,000 PW3

21,000PW4

200,000 PW5

147,000PW2

595,000PW3

4* 2810(Playa*)

1870(Playa*)

5270PW5

172 PW4

1111 playa

2490(Playa*)

8750 PW5

Truth 20,940 PW2

18,887 PW2

15,366 PW3

217 PW4

651 PW4

20,187 PW2

574PW3

Particle Tracking Resultstravel time (yr) & exit location

PEST?Low porosity gives high velocitywhich yields short travel times.

6 hits

*PW2 went dry.or Luck?

2008 Results

Calibration Prediction

Group ARM h

ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)*

1 1.16 0.20 2.87 5.02

2 0.8 0.52 1.81 2.27

3 1.18 0.47 2.73 12.77

4 2.39 0.78 0.80 0.76

5 2.07 1.10 1.61 2.61

6 0.96 0.48 2.13 2.90

7 0.92 0.96 1.18 0.92

8 0.50 0.60 3.70 2.71

9 0.054 0.0049 3.54 5.52

2006Project Results

Despite the relativelypoor calibration, groups4 and 5 managed tocapture the essentialfeatures of the systemfor the purpose of the prediction.

Group

P1 P2 P3 P4 P5 P6 P7

1 5450 playa

2561 PW2 5060 playa 1098 PW4

401 PW4 1465 playa

1220 PW2

2 2120 PW2 606 PW2 709 playa 474 PW4

595 PW4 608 playa

310 PW3

3 5247 PW2 1088 PW2 1599 playa 361 PW4

510 PW4 2317 PW1

2243 playa

4 6601 playa

1226 PW2 592 playa 623 PW4

846 PW4 968 playa

1194 PW2

5 4548 playa

1660 PW2 1513 playa 1412 PW4

744 PW4 817 PW1 4410 playa

6 1.20E5 PW5

820 PW2 1.82 E4 PW5

587 PW4

576 PW4 1.19 E5 PW5

9990 PW5

7 4083 playa

1039 PW2 618 playa 647 PW4

629 PW4 908 playa

2484 PW2

8 2810 PW2 986 PW2 752 playa 659 PW4

577 PW4 359 PW1 502 PW3

9 546 PW1 534 PW2 1156 playa 402 PW4

1121 playa

91 PW1 1170 PW2

Truth 672 PW1

549 PW2

1.25 E5 playa

359 PW4

650 PW4

238 PW1

1712 playa

Particle Tracking Resultstravel time (yr) & exit location

5 hits

6 hits

2006Project Results

Group P1 P2 P3 P4 P5 P6 P7

1 4507PW2

2100 PW2

461,423 PW2

220 PW4

3956 playa

24,923PW2

1395 PW2

2 719PW2

253 PW2

2192 PW2

86PW4

5874 PW2

540PW2

2424PW2

3 87,800PW2

114,000 PW2

646,000 PW3

21,000PW4

200,000 PW5

147,000PW2

595,000PW3

4 2810(Playa)

1870(Playa)

5270PW5

172 PW4

1111 playa

2490(Playa)

8750 PW5

Truth 20,940 PW2

18,887 PW2

15,366 PW3

217 PW4

651 PW4

20,187 PW2

574PW3

6 hits

Calibration Prediction

Group ARM h ARM ET (x10e7)

ARM h (at targets)

ARM h(at pumping wells)**

3 0.93 0.74 6.12 3.57

PEST?or Luck?

Group 3 managed to capture the essentialfeatures of the system for the best pumpingprediction and the best prediction of particleexit points, but not travel times.

2008 Results

Generally predicted ARM at targets > Calibrated ARM

Generally, predicted ARM at pumping wells > Predicted ARM at nodes with targets

Head predictions are more robust (consistent among different calibrated models) than transport (particle tracking) predictions.

Observations

To use conventional inverse models/parameter estimationmodels in calibration, you need to have a pretty good idea of zonation (of K, for example).

Also need to identify reasonable ranges for thecalibration parameters.

(New version of PEST with pilot points does not need zonation as it works with continuous distribution of parameter values.)

Calibration to Fluxes

When recharge rate (R) is a calibration parameter, calibrating to fluxes can help in estimating K and/or R.

R was not a calibration parameter in our problem.

H1H2

q = KI

In this example, flux information helps calibrate K.

or discharge information helps calibrate R.

All water discharges to the playa.Calibration to ET merely fine tunesthe discharge rates within the playaarea. Calibration to ET does nothelp calibrate the heads and K valuesexcept in the immediate vicinityof the playa.

In our example, total recharge is known/assumed to be 7.14E08 ft3/year and discharge = recharge.

Conclusions• Calibrations are non-unique.

• A good calibration (even if ARM = 0) does not ensure that the model will make good predictions.

• Need for an uncertainty analysis to accompany calibration results and predictions.

• Field data are essential in constraining the model so that the model can capture the essential features of the system.

• Modelers need to maintain a healthy skepticism about their results.