Title: Long-Term Salinity Prediction with Uncertainty Analysis: Application for Colorado River Above Glenwood Springs, CO
1Long-Term Salinity Prediction with Uncertainty
AnalysisApplication for Colorado River Above
Glenwood Springs, CO
Hydrology Days 2002
- James Prairie
- Water Resources Division, Civil, Architectural,
and Environmental Engineering Department, and
U.S. Bureau of Reclamation, University of
Colorado, Boulder - Balaji Rajagopalan
- Water Resources Division, Civil, Architectural,
and Environmental Engineering Department,
University of Colorado, Boulder - Terry Fulp
- U.S. Bureau of Reclamation, University of
Colorado, Boulder - Edith Zagona
- Center for Advanced Decision Support for Water
and Environmental Sysytems (CADSWES), University
of Colorado, Boulder
2Motivation
- Colorado River Basin
- arid and semi-arid climates
- irrigation demands for agriculture
- Law of the River
- Mexico Treaty Minute No. 242
- Colorado River Basin Salinity Control Act of 1974
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4Existing Salt Model Over-Prediction
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6Stochastic Simulation
- Simulate from the conditional probability
function - joint over the marginal densities
7Parametric PAR(1)
- Periodic Auto Regressive model (PAR)
- developed a lag(1) model
- Stochastic Analysis, Modeling, and Simulation
(SAMS) (Salas, 1992) - Data must fit a Gaussian distribution
- Expected to preserve
- mean, standard deviation, lag(1) correlation
- skew dependant on transformation
- gaussian probability density function
8Modified Nonparametric K-NN Natural Flow Model
- Improvement on traditional K-NN
- keeps modeling simple yet creates values not seen
in the historic record - perturbs the historic record within its
representative neighborhood - allows extrapolation beyond sample
9Residual Resampling
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14Conditional PDF
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16Statistical 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
17Comparison with Observed Historic Salt
18Comparison With Calculated Natural Salt
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20CRSS Simulation Model for Historic Validation
Natural flow 1906-95 Natural salt 1941-95
Constant salinity pickup 137,000 tons/year
Exports removed _at_ 100 mg/L
Compare results to observed historic for
validation
21Annual Model With Resampling
- Based on 1941-1995 natural flow
- 1941-1995 annual salt model
- Simulates 1941-1995
- Historic Flow and Concentration
22Modified and Existing CRSS Comparison Historic
Salt Mass
- Based on 1906-1995 natural flows
- 1941-1995 monthly salt models
- Simulates 1941-1995
23Policy AnalysisHistoric Simulation
gt 650,000 tons salt
gt 350 mg/L salt concentration
24Stochastic Planning Runs Projected Future Flow
and Salt Mass
- Passing gauge 09072500
- Based on 1906-1995 natural flows
- 1941-1995 monthly salt models
- Simulating 2002 to 2062
25Conclusion
- Developed a modeling framework for long-term
salinity with uncertainty in the Colorado River - modified nonparametric K-NN natural flow model
- statistical nonparametric natural salt model
- validation of historic record
- demonstrated future projection
26Future Work
- Extend the modified K-NN flow model to perform
space-time dissaggregation to simulate flow and
salt over the entire basin - Move operational policy to an annual time step
- Further research into the relationship between
salt loading and land use - Continue work to incorporate climate information
in streamflow generation
27Acknowledgements
- Balaji Rajagopalan, Terry Fulp, 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
28Extra Slides Follow
29Conclusions
- developed and tested a new statistical
nonparametric natural salt model - discussed nonparametric techniques
- flexible and easy to implement
- can preserve any arbitrary distribution
- conditioning with additional data
- validation of historic record
- preservation of historic salinity violations
30Case Study
- Colorado River above USGS gauge 09072500
(Colorado River near Glenwood Springs, CO) - flow data available from water year 1906-1995
- salt data available from water year 1941-1995
- model at a monthly timestep to accommodate the
reservoirs operating policy in the simulation
model
31Motivation
- Generating synthetic natural flow
- future variability
- Index Sequential Method (ISM)
- cannot produce values or traces that had not
occurred in the past - limited variability among traces
32ENSO response in Colorado River Basin
- Published by Cayan and Webb, 1992
- A weak response seen over Upper Colorado River
Basin
33Sea Surface Temperature
Correlation
Sea Level Pressure
34Residual Resampling
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et
yt
Alpha 0.4 or k 18
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35Model Validation Natural Flow
- 1941-1995 natural flow
- Utilizes subset of available record
36Model Validation Natural Flow
- 1906-1995 natural flow
- Utilizes entire available record
37Model Validation Natural Salt Mass
- 1941-1995 natural flow
- Utilizes subset of available record
- 1941-1995 monthly and annual salt model
38Model Validation Natural Salt Mass
- 1906-1995 natural flow
- 1941-1995 monthly salt models
39Annual model with no resampling
- 1906-1995 natural flow
- 1941-1995 annual salt model
- Historic Flow and Concentration
40Future Salt Mass
41Motivation
- Salinity Control Forum
- Federal Water Pollution Control Act Amendments of
1972 - Numerical salinity criteria
- 723 mg/L below Hoover Dam
- 747 mg/L below Parker Dam
- 879 mg/L at Imperial Dam
- review standards on 3 year intervals
- Develop basin wide plan for salinity control
42Existing Colorado River Simulation System (CRSS)
- Includes three interconnected models
- salt regression model
- USGS salt model
- stochastic natural flow model
- index sequential method
- simulation model of entire Colorado River basin
- implemented in RiverWare
43Index Sequential Method
- Current stochastic hydrology model utilized by
the USBR
Adapted from Ouarda, 1997
44Model Evaluation
- Natural flow 1906 to 1995
- Basic Statistics
- mean,standard deviation, autocorrelation,
skewness - Higher Order Statistics
- probability density function
- conditional probability
- Minimum and Maximum Flows
45USGS 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)
46Policy AnalysisHistoric Simulation
- gt 350 mg/L salt concentration
Incorporates total depletion as a function of
natural flow
47CRSS Simulation Model for Future Prediction
- Natural flows based on 1906-1995
- Natural salt model based on 1941-1995
- Projected depletions 2002-2062
- Constant Ag salt loading of 137,000 tons/year
- Constant salt removal with exports of 100
mg/L/year
48Policy Analysis Future Projections
gt 750,000 tons salt
gt 600 mg/L salt concentration