Investigating the Colorado River Simulation Model

James Prairie

Bureau of Reclamation

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

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

Seminar Outline

Motivation for researchInitial findings Working with a case studyNew salinity modeling techniquesExtending knowledge of our case studyCurrent Efforts

Recompute Natural flowVerify entire Colorado River Simulation Model

Future Research

Colorado River below Imperial Dam, Ariz-Calif

550

650

750

850

950

1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995

TD

S (

mg

/L)

0

10,000

20,000

30,000

40,000

Flo

w 1

,000

(ac

-ft)

TDS Flow

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

Investigation of Colorado River Simulation Model

First developed in Fortran in 1970’sMoved to RiverWare in 1990’sRelies on Conservation of Mass for modeling

water quantity and,water quality (TDS).

Monthly Time StepRuns with operational rules to simulate

operational policies in the Colorado River Basin

Initial Findings

Data and Methodological InconsistencyNeed to improve current model techniques

Stochastic stream flow simulationEstimating natural saltAdding uncertainty

Working with a case studyDetailed investigation of current methodsDevelopment of new methods

USGS gauge 09072500

(Colorado River near Glenwood Springs, CO)

• Historic flow from 1906 - 95

• Historic salt from 1941 - 95

Case Study Area

USGS Salt Model

12 monthly regressionsbased on observed historic flow and salt

mass from water year 1941 to 1983historic salt = f (historic flow, several

development variables)

natural salt = f (natural flow, development variables set to zero)

Existing Salt Model Over-Prediction

New Modeling Techniques

Found problems with the current method to estimate natural salt in the upper basinCan we fix the problem?Alternate methods the estimate natural salt

with the available data

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

Local Regression

alpha = 0.3

or 27 neighbors

X

Y

x

y * e *

Residual Resampling

y = y* + e*

Y

X

Nonparametric Salt Model and USGS Salt Model

Natural Salt Mass from Nonparametric Salt Model and USGS Salt Model

USGS Salt Model and New Salt Model with K-NN Resampling Comparison

Comparison with Observed Historic Salt

Key Case Study Findings

The new nonparametric salt model removed the over-prediction seen with the USGS salt model

Provides uncertainty estimatesCan capture any arbitrary relationship

(linear or nonlinear)

Extending from Case Study

Applying case study results to entire modelImproved natural salt estimation modelImproved stochastic stream flow generationAddition of uncertainty analysis

Ensure flexible framework

Current Efforts

Recomputing natural flowLack of base dataUndocumented procedure

Upper versus Lower Basin

Inconsistency across time periodsInconsistent with future projection model

Natural Flow Development

Natural flow is a basic input for CRSSAddressing Data Inconsistencies

Recomputing natural flow from 1971-95

Natural Flow = Historic Flow

- Consumptive Uses and Losses

+/- Reservoir Regulation

Addressing Methodological InconsistenciesRiverWare model computes natural flow

Ensures consistency

Recomputing natural flow from 1971-95

Data required for natural flow modelHistoric USGS gauge data

29 gauges

Historic main-stem reservoir outflow and pool elevations12 main-stem reservoirs

Historic off-stream reservoir change in storage22 off-stream reservoirs

Consumptive uses and losses9 categories

Determining Natural Flow

saltflow

historic agriculture

historic exports

historic municipal and industrial

historic effects of off-stream

calculated natural flow estimated natural salt mass

simulated historic flow simulated historic salt mass

USGS stream gauge 09072500

consumptive useirrigatedlands

reservoir regulation

salt loadings

salt removedwith exports

agricultural

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

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

Acknowledgements

Dr. Balaji Rajagopalan, Dr. Terry Fulp, Dr. Edith Zagona for advising and support

Upper Colorado Regional Officeof the US Bureau of Reclamation, in particular Dave Trueman for funding and support

CADSWES personnel for use of their knowledge and computing facilities

Drainage AreaColorado River

Basin241,000 mi2

Upper Basin110,000 mi2

Case Study4,558 mi2