sediment land calibration: status and decision rules

Chesapeake Bay Program Modeling

Sediment Land Calibration:

Status and Decision Rules

Chesapeake Bay Program Modeling

Land-River Connection in HSPF

BMP Factor

Land Acre FactorDelivery Factor

Edge of Field

Edge of Stream

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Corresponding to model structure, calibration strategies break into…

• Land calibration

• River Calibration

Chesapeake Bay Program Modeling

Land Sediment Simulation

J1= KSER * RO *(RO + Water Storage)

Detached Sediment

Soil Matrix(unlimited)

Wash off

Det

achm

ent

Att

achm

ent

= (1-cover) * KRER* (Rain) J2

= AFFIX * (Detached sediment)

= NVSI lb/day

Input

Chesapeake Bay Program Modeling

• Calibrate Edge of Field to targets

• Split into major land uses

Land Calibration

Chesapeake Bay Program Modeling

13 Land use categories for sediment:

Group 2 –

• Harvested Forest• Natural grass• Extractive• Barren• Pervious Urban• Impervious Urban• water

Group 1 –

• Forest• Pasture• Hay • High till with manure• High till without

manure• Low till with manure

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EOF Targets

• For each land use in group 1: EOF targets available at county level

RUSLE supplied by NRI

• For each land use in group 2: Single EOF target obtained from

literature

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Land EOF calibration

• For each land use in group 1, reach EOF

targets county by county

Total = 6 land use X 308 counties

= 1848

• For each land use in group 2, reach single

target for the entire watershed

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Iterative Calibration• Wrote computer programs to automatically

calibrate EOF for all land use and all counties

• Started with parameter set from manual calibration

• Developed rules for adjusting parameter values based on model outputs

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Decision Rules for Four Key land Parameters:

• Rule1 – detached sed reach 90% of max sediment in 30 days

AFFIX = 0.07673

Detached Sediment

Att

achm

ent

= AFFIX * (Detached sediment)

)1( *tAFFIXeAFFIX

NVSIS

SAFFIXNVSIdt

dS*

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• Rule2 – Vertical Input high enough for hysteresis

NVSI (lb/acre/day)= a * target load (lb/acre/yr) a - changeable parameter Assumed a =0.5

for hvf grs pur … NVSI 0.93 9.32 4.11 3.01 …

Detached Sediment= NVSI lb/day

Input

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• Rule 3 - Zero Detached Sed after Large Storms

Adjust KRER and KSER to ensure

- No build-up after most big storms

- Reach to targets

Ratio of KSER:KRER = b (changeable)

Enforced minimum and maximum values

Chesapeake Bay Program Modeling

Decision Rules

PARAMETERS

for hvf grs pas hay hom hwm lwm pur ext bar

AFFIX, 0.07673

NVSI, 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

KS-KR, 2 2 2 2 2 2 2 2 2 2 2

*** min and max allowed by user and by HSPF

KRER, 0.01 50. 0.0 100.

KSER, 0.01 100. 0.0 200.

Chesapeake Bay Program Modeling

Expected results:

• Land segment A42033

0

0.5

1

1.5

2

2.5

12/20/83 09/15/86 06/11/89 03/07/92 12/02/94 08/28/97 05/24/00

SURO

DETS

WSSD

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300

SURO

DETS

WSSD

Chesapeake Bay Program Modeling

Eight Scenarios tested

Scenarios a (NVSI/Target) KSER:KRER 1 0.5 2 2 0.6 2 3 0.7 2 4 0.8 2 5 0.5 2.5 6 0.5 3 7 0.6 2.5 8 0.6 3

Chesapeake Bay Program Modeling

Scenarios with same KSER:KRER ratioKSER:KRER =2

0

1

2

3

4

5

6

7

0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85

NVSI /Target

Avera

ge d

ets

(to

ns)

for

hvf

grs

pas

hay

hom

hwm

lwm

pur

ext

bar

KSER:KRER =2

05

1015202530354045

0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85

NVSI/Target

Ave

rag

e K

SE

R

for

hvf

grs

pas

hay

hom

hwm

lwm

pur

ext

bar

Chesapeake Bay Program Modeling

Scenarios with same NVSI/Target ratio

NVSI/Target =0.5

0

12

3

45

6

1.5 2 2.5 3 3.5

KSER:KRER

Avera

ge D

ets

(to

ns)

for

hvf

grs

pas

hay

hom

hwm

lwm

pur

ext

bar

NVSI/Target =0.5

0

10

20

30

40

50

1.5 2 2.5 3 3.5

KSER:KRER

Avera

ge K

SE

R

for

hvf

grs

pas

hay

hom

hwm

lwm

pur

ext

bar

Chesapeake Bay Program Modeling

Status and expected steps

• Computer programs ready

• EOF calibration can be done in 2~3 days

once final land use and hydrology

parameters available

Chesapeake Bay Program Modeling

Land-River Connection

BMP Factor

Land Acre FactorDelivery Factor

Edge of Field

Edge of Stream

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River Calibration…

• Have started manual calibration

• Calibrate to three sediment rating curves, statistics…

• Hope to develop iterative calibration based on manual practice

Chesapeake Bay Program Modeling