Investigating the Colorado River Simulation Model

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Investigating the Colorado River Simulation Model

• James Prairie
• Bureau of Reclamation

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Motivation

• Colorado River Basin
• arid and semi-arid climates
• irrigation demands for agriculture
• Federal Water Pollution Control Act Amendments of
  1972
• Law of the River
• Minute No. 242 of the International Boundary and
  Water Commission dated August 30, 1973
• Colorado River Basin Salinity Control Act of 1974

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Salinity Damages and Control Efforts

• Damages are presently, aprox. 330 million/year
• As of 1998 salinity control projects has removed
  an estimated 634 Ktons of salt from the river
• total expenditure through 1998 426 million
• Proposed projects will remove an additional 390
  Ktons
• projects additional expenditure 170 million
• Additional 453 Ktons of salinity controls needed
  by 2015

Data taken from Quality of Water, Progress Report
19, 1999 Progress Report 20,2001
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Seminar Outline

• Motivation for research
• Initial findings
• Working with a case study
• New salinity modeling techniques
• Extending knowledge of our case study
• Current Efforts
• Recompute Natural flow
• Verify entire Colorado River Simulation Model
• Future Research

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Research Objectives

• Verify the data and calibrate the current model
  for both water quantity and water quality (total
  dissolved solids, or TDS)
• Investigate the salinity methodologies currently
  used and improving them as necessary for future
  projection

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Investigation of Colorado River Simulation Model

• First developed in Fortran in 1970s
• Moved to RiverWare in 1990s
• Relies on Conservation of Mass for modeling
• water quantity and,
• water quality (TDS).
• Monthly Time Step
• Runs with operational rules to simulate
  operational policies in the Colorado River Basin

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Initial Findings

• Data and Methodological Inconsistency
• Need to improve current model techniques
• Stochastic stream flow simulation
• Estimating natural salt
• Adding uncertainty
• Working with a case study
• Detailed investigation of current methods
• Development of new methods

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Case Study Area

• Historic flow from 1906 - 95
• Historic salt from 1941 - 95

USGS gauge 09072500 (Colorado River near Glenwood
Springs, CO)
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USGS Salt Model

• 12 monthly regressions
• based on observed historic flow and salt mass
  from water year 1941 to 1983
• historic salt f (historic flow, several
  development variables)
• natural salt f (natural flow, development
  variables set to zero)

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Existing Salt Model Over-Prediction
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New Modeling Techniques

• Found problems with the current method to
  estimate natural salt in the upper basin
• Can we fix the problem?
• Alternate methods the estimate natural salt with
  the available data

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Statistical Nonparametric Model for Natural Salt
Estimation

• Based on calculated natural flow and natural salt
  mass from water year 1941-85
• calculated natural flow observed historic
  flow total depletions
• calculated natural salt observed historic
  salt - salt added from agriculture salt
  removed with exports
• Nonparametric regression (local regression)
• natural salt f (natural flow)
• Residual resampling

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Local Regression
alpha 0.3 or 27 neighbors
Y
X
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Residual Resampling
y y e
Y
X
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Nonparametric Salt Model and USGS Salt Model
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Natural Salt Mass from Nonparametric Salt Model
and USGS Salt Model
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USGS Salt Model and New Salt Model with K-NN
Resampling Comparison
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Comparison with Observed Historic Salt
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Key Case Study Findings

• The new nonparametric salt model removed the
  over-prediction seen with the USGS salt model
• Provides uncertainty estimates
• Can capture any arbitrary relationship (linear or
  nonlinear)

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Extending from Case Study

• Applying case study results to entire model
• Improved natural salt estimation model
• Improved stochastic stream flow generation
• Addition of uncertainty analysis
• Ensure flexible framework

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Current Efforts

• Recomputing natural flow
• Lack of base data
• Undocumented procedure
• Upper versus Lower Basin
• Inconsistency across time periods
• Inconsistent with future projection model

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Natural Flow Development

• Natural flow is a basic input for CRSS
• Addressing Data Inconsistencies
• Recomputing natural flow from 1971-95
• Natural Flow Historic Flow
• - Consumptive
  Uses and Losses
• /- Reservoir Regulation
• Addressing Methodological Inconsistencies
• RiverWare model computes natural flow
• Ensures consistency

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Recomputing natural flow from 1971-95

• Data required for natural flow model
• Historic USGS gauge data
• 29 gauges
• Historic main-stem reservoir outflow and pool
  elevations
• 12 main-stem reservoirs
• Historic off-stream reservoir change in storage
• 22 off-stream reservoirs
• Consumptive uses and losses
• 9 categories

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Determining Natural Flow
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After Natural Flow Is Calculated

• Extend new natural salt model throughout the 21
  upper basin natural flow gauges
• Check natural flow and salt relationship
• 1941-1995 1970-1995
• Calculate natural flow for the lower basin
• Natural salt is back calculated as flow
• Verify entire basin for flow and the lower basin
  for salt
• Finally use more for a future projection

• Apr-Jul 2003
• Aug-Sep 2003
• Oct-Nov 2003
• Dec 2003

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Future Research

• Explore salinity relationship over both space and
  time
• Incorporate new stochastic flow generation
  methods
• Investigate land use change and the impacts on
  salinity levels
• Explore the relationship between basin area and
  both flow and salinity

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Acknowledgements

• Dr. Balaji Rajagopalan, Dr. Terry Fulp, Dr. Edith
  Zagona for advising and support
• Upper Colorado Regional Office
• of the US Bureau of Reclamation,
• in particular Dave Trueman for funding and
  support
• CADSWES personnel for use of their
• knowledge and computing facilities

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• Drainage Area
• Colorado River Basin
• 241,000 mi2
• Upper Basin
• 110,000 mi2
• Case Study
• 4,558 mi2