watersupply (2).ppt
TRANSCRIPT
7/27/2019 WaterSupply (2).ppt
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Water Supply Study
Present and Planned Water Supply
• Operational (2001) spring water bottling plant,
with groundwater extraction rates
approximating 125 gpm.• Planned groundwater extraction of up to 400
gpm.
• Concerns about impacts to nearby water
bodies.
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Critical Prediction
Calcu late changes in Sur face-
Water Flow s, Wetland and Lake Levels from Constant
Produc t ion of 400 gpm
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0ft 10000ft 20000ft
Regional Model Design
Study Area
Selected CodeMODFLOW2000
Model Summary4 layers
Conductivity zones derived from
regional/local geologic studies
Variable recharge derived from
published regression analysis
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Local Model Area
Impoundment
Stream
Pumping
Center
Spring
Outfall
Groundwater
Flow
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Shortcomings in Problem
FormulationModeling Tool – Use of River Package
• Inability to realistically represent changes
in streams, wetlands, and lakes.
• Inability to explicitly represent the
impoundment-overflow
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Stream
Impoundment Culvert
Discharge
Stream
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Revised Problem Formulation
• Digitized stream intersections and topo maps to assign
MODFLOW Drain/River - revised during calibration.
• Impoundment and nearby lakes represented with Lake
Package (Merritt and Konikow, 2000); outflow fromimpoundment explicitly modeled.
• Four wetlands with standing water modeled with Lake
Package to explicitly simulate wetland water levels.
• Stream simulated using MODFLOW Drain Package
plus Impoundment outflow.
• Regional river comprises down gradient drainage
center.
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Model Calibration
Calibration Strategy
• Steady-state calibration to water levels in 48 wells,
baseflow in five creeks, and lake levels in five lakes.
• Transient calibration to drawdowns from long-term (72hour) pumping test - one dozen wells with time-series
drawdown data
• Prior information used to establish total transmissivity
as ‘soft’ information during steady-state calibration
• Approx. 40 parameters – step-wise reduction using
tied/untied parameters as calibration progressed
• PEST used in parallel across four 1.8GHz processors
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PEST Pre-Post Processing
Advantages over GUI or ‘prompt’ Execution
• Ability to assess progress with every run
• Ability to re-parameterize (tie, hold, transform, scale,
prior, regularize) model without ‘rebuild’
• Ability to alter run type with one (or two) quick Control
File modifications – Forward run, Estimation,
Regularization, and Prediction
goto 20
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goto 20
Open(1,file='MICHIGAN_No_Reaches.riv')
Open(2,file='Michigan_reaches.riv')
c MODFLOW 2000 headers
Read(1,*)
Read(1,*)
Read(1,*) nriv,idum
Write(2,'(2I10)') nriv,idum
Read(1,*) nriv
Write(2,*) nriv
c Lay, Row, Col
Do n=1,nrivRead(1,*) k,i,j,stage,cond,rbot
Write(2,2) k,i,j,stage,cond*10,rbot,iriv_rch(j,i)
End do
Close(1)
Close(2)
Open(1,file='MICHIGAN_No_Reaches.drn')
Open(2,file='Michigan_reaches.drn')
c MODFLOW 2000 headers
Read(1,*)
Read(1,*)
Read(1,*) nriv,idum
Write(2,'(2I10)') nriv,idum
Read(1,*) nriv
Write(2,*) nriv
Do n=1,nriv
c Lay, Row, Col
Read(1,*) k,i,j,rbot,cond
Write(2,3) k,i,j,rbot,cond,idrn_rch(j,i)
End do
Close(1)
Close(2)
20 Continue
c=======================================================================
c FORMAT STATEMENTS
c=======================================================================
1 Format(4I11,F21.0)
2 Format(3I10,F10.3,E10.3,F10.3,I10)
3 Format(3I10,F10.3,E10.3,I10)
c=======================================================================
c END OF PROGRAM
c=======================================================================
STOP 'Normal Exit'
END
Batch File
Batch and Post-Processing
Post-Processor REM File Management
del headsave.hds
copy mich_fin.hds headsave.hds
del mich_fin.hds
del mich_fin.ddn
del calibration.hds
REM Run array multiplerscond_mult
rech_mult
REM Run custom MF2K Lake Package
cust_lak3 <modflowq.in
REM get the water level target data
targpest
REM get the flux target data
flux_targets
copy mich_fin.hds calibration.hds
REM Check for water above land surface
wl_above_ls
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Calibration Results – SS
Baseflows Water Levels
0.E+00
1.E+06
2.E+06
3.E+06
4.E+06
0.E+00 1.E+06 2.E+06 3.E+06 4.E+06
940.0
960.0
980.0
1000.0
1020.0
1040.0
9.4E+02 9.6E+02 9.8E+02 1.0E+03 1.0E+03 1.0E+03
WL Sum of Squares (PHI) = ~ 115 ft2
Count = 48 wells
Mean Residual = - 0.2 ft
Mean Absolute Residual = 1.1 ft
StDev of the residuals = 1.5 ft
Range = 63 ftStDev/Range = ~ 2.25%
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Calibration Results – Transient
Drawdowns
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Predictive Analysis
Problem Formulation and Execution
• Reformulate the PEST calibration control file to
estimate the max and min baseflow depletions in
stream, while maintaining calibration – i.e. establishthe range of uncertainty
• Typically the increment added to the calibration
objective function (Fmin + d) is about 5% of Fmin.
For our analysis, this was raised by 50%
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Predictive Analysis
Present and Planned Water Supply
• With total planned groundwater extraction of 400 gpm.
-Predicted stream depletion at regional river: 400 gpm
-Depletion of interest stream: small but measurable*
-Changes in wetland water levels: small but measurable*
The calculated upper- and lower-bound estimates of the change in flow
at the stream are on the order of five percent (above or below) of the
‘most likely’ estimated change.
*This is consistent with the observation that wetland water levels, and the areal extent of wetlands based on aerial photographs were not significantly affected by the construction of
the impoundment .
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Salient Point(s)
• Problem formulation is key to the ‘integrity’ of the
predictive analysis – the selected code must be
designed to simulate the type of prediction of
interest.
• The fairly tight bounds on the prediction may also
arise from the ability of models to predict changes
far better than absolute numbers.