Gopal Bhatt1 and Gary Shenk2

1 Penn State, 2 USGS

11/28/2017

Phase 6 Chesapeake Bay Watershed Model – Final Calibration

Modeling Workgroup Conference Call – November 2017

Presentation outline

Review of final re-calibration State-basin summary of delivered loads

2

Final re-calibration

A detailed presentation on the updates included in the final re-calibration was made in the October modeling workgroup quarterly meeting [1].

The updates include: Partnership review comments for both inputs and model. USGS-SPARROW Nitrogen land to water delivery variance factors

were excluded. Flow weighted observations were used. Chesapeake floodplain network (CFN) observations (not

regressions) were used for estimating stream loads. Organic scour processes were added.

The post auto-calibration phase included further refinements of the model performance, calibration of time-variable Conowingo infill, and parametrization of ungagedriver segments.

[1] https://www.chesapeakebay.net/channel_files/24721/20171017_-_bhatt_-_cbp_-_october_recalibraion_2.pdf 3

Model performance across spatial scalesaverage annual loads at WRTDS sites

NITROGENPHASE 5

30 ESTIMATOR sites(with regional factors)

51E3 1E4 1E5 1E6 1E7 1E8 1E9

1E3

1E4

1E

5

1E6

1E7

1

E8

1E9

NSE 0.994

Log NSE 0.981 Susquehanna at Conowingo, MD27086 sq. miles

NW Branch Anacostia River near Hyattsville, MD

52 sq. miles

NITROGENPHASE 6

77 WRTDS sites

61E3 1E4 1E5 1E6 1E7 1E8 1E9

1E3

1E4

1E

5

1E6

1E7

1

E8

1E9

NSE 0.998

Log NSE 0.996

S F Quantico Creek near Independent Hill, VA

7.4 sq. miles

Susquehanna at Conowingo, MD27086 sq. miles

PHOSPHORUSPHASE 5

71E3 1E4 1E5 1E6 1E7 1E8

1E3

1

E4

1E

5

1E6

1E7

1

E8

30 ESTIMATOR sites(with regional factors)

NSE 0.966

Log NSE 0.962

PHOSPHORUSPHASE 6

81E3 1E4 1E5 1E6 1E7 1E8

1E3

1

E4

1E

5

1E6

1E7

1

E8

61 WRTDS sites

NSE 0.997

Log NSE 0.989

SEDIMENTPHASE 5

9

1E4 1E5 1E6 1E7 1E8 1E9 1E10 1E11

30 ESTIMATOR basins

1E4

1E5

1E6

1

E7

1

E8

1

E9

1

E10

1

E11

NSE 0.323

Log NSE 0.732

SEDIMENTPHASE 6

10

1E4 1E5 1E6 1E7 1E8 1E9 1E10 1E11

60 WRTDS basins

1E4

1E5

1E6

1

E7

1

E8

1

E9

1

E10

1

E11

NSE 0.987

Log NSE 0.990

Model performance in resolving heterogeneityaverage annual per acre loads at WRTDS sites

Review of geographic efficiencies

12

WRTDS and simulated per acre loads are compared.

Nash-Sutcliffe model efficiency was used to quantify the predictive power of the model across the watershed.

An efficiency of 1 would indicate a perfect match in loads for all river basins (where WRTDS estimates are available).

Phase 5 – geographic efficiencies

13WRTDS Per Acre Load

Sim

ulat

ed P

er A

cre

Load

Higher NSE indicates better model performance.

Phase 6 – geographic efficiencies

14WRTDS Per Acre Load

Sim

ulat

ed P

er A

cre

Load

Summary of geographic efficiencies

Constituents Phase 5 Phase 6

Nitrate 0.8284 0.9547

Nitrogen 0.8704 0.9747

Phosphorus 0.6321 0.9565

Sediment -0.0770 0.9649

15

Higher NSE indicates better model performance.

Temporal/seasonal model performancethe correlation of simulated and WRTDS monthly loads

Correlation of monthly loads: total nitrogen

17Higher correlation coefficient indicates better model performance.

Correlation of monthly loads: total phosphorus

18Higher correlation coefficient indicates better model performance.

Correlation of monthly loads: sediment

19Higher correlation coefficient indicates better model performance.

Model performance in loading estuarine modelaverage annual loads at RIM sites

RIM loads: total nitrogen

assuming +/- 10% uncertainty in WRTDS estimates21

BASIN Phase 6 June Draft Phase 5SUSQ -06% -03% -01%POTO -04% -09% -22%JAME -03% -02% -07%RAPP -01% -07% -10%APPO -01% -07% -02%PAMU -01% 00% 06%MATT 04% 07% -06%PATU 04% 05% 19%CHOP -02% 08% -13%

RIM loads: total phosphorus

assuming +/- 15% uncertainty in WRTDS estimates22

BASIN Phase 6 June Draft Phase 5SUSQ 01% 07% 10%POTO 01% -01% -14%JAME -01% 10% -25%RAPP -01% 06% 02%APPO 02% 13% 04%PAMU 03% 12% 07%MATT 01% -13% 04%PATU 00% 08% -18%CHOP -12% 13% 22%

RIM loads: sediment

assuming +/- 15% uncertainty in WRTDS estimates23

BASIN Phase 6 June Draft Phase 5SUSQ 07% -11% 01%POTO 03% -29% -45%JAME 01% -13% -58%RAPP 00% 26% -29%APPO 14% 36% 75%PAMU 02% 40% 10%MATT -01% 90% 57%PATU 12% 53% 22%CHOP 03% 171% 71%

State-basin loads:

Review of Phase 5 and Phase 6 state-basin loads delivery to the Bay (1991-2000) –

24

NITROGENCalibration

25Average annual delivery for 1991-2000

Phase 5: Nitrogen – MD Potomac

26

27

Phase 6: Nitrogen – MD Potomac

PHOSPHORUSCalibration

28Average annual delivery for 1991-2000

29

Phase 5: Phosphorus – MD Potomac

30

Phase 6: Phosphorus – MD Potomac

Summary and Conclusions

Phase 6 Watershed Model was re-calibrated to incorporate final partnership inputs and review comments. The model performed quite well for several key

performance evaluation metrics. The corresponding state-basin summary of loads were

shown.Work is needed to document several aspects of model

development, calibration, and its application.

Calibration related information, such as calibration figures, comparison with WRTDS loads, are available at ftp://ftp.chesapeakebay.net/Modeling/Phase6/Phase_6_201710/Watershed_Model/

31

Appendices

32

NITRATEPHASE 5

16 ESTIMATOR basins

331E3 1E4 1E5 1E6 1E7 1E8 1E9

1E3

1E4

1E

5

1

E6

1E7

1E8

1E

9

NSE 0.900

Log NSE 0.965

NITRATEJUNE DRAFT

77 WRTDS Stations

341E3 1E4 1E5 1E6 1E7 1E8 1E9

1E3

1E4

1E

5

1

E6

1E7

1E8

1E

9

NSE 0.994

Log NSE 0.971

NITRATEPHASE 6

77 WRTDS Stations

351E3 1E4 1E5 1E6 1E7 1E8 1E9

1E3

1E4

1E

5

1

E6

1E7

1E8

1E

9

NSE 0.996

Log NSE 0.992

DISSOLVED PHOSPHATEPHASE 5

361E2 1E3 1E4 1E5 1E6 1E7 1E8

1E2

1E

3

1E4

1

E5

1E6

1

E7

1E8

61 WRTDS Stations

NSE -3.195

Log NSE 0.540

JUNE DRAFT

37

61 WRTDS Stations

DISSOLVED PHOSPHATE

1E2 1E3 1E4 1E5 1E6 1E7 1E8

1E2

1E

3

1E4

1

E5

1E6

1

E7

1E8

NSE 0.892

Log NSE 0.974

PHASE 6

38

61 WRTDS Stations

DISSOLVED PHOSPHATE

1E2 1E3 1E4 1E5 1E6 1E7 1E8

1E2

1E

3

1E4

1

E5

1E6

1

E7

1E8

NSE 0.871

Log NSE 0.981

Monthly loads: nitrate

39

Monthly loads: dissolved phosphate

40

State – basin loads: Nitrogen (1991-2000)

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

State – basin loads: Phosphorus (1991-2000)

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118