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Water Supply Forecasting Research at UNLV

Thomas Piechota, PhD, P.E.Director of Sustainability and Multidisciplinary Research

Associate Professor, Department of Civil and Environmental Engineering

Kenneth Lamb, P.E.

Funded By: NOAA

Outline

Climate Variability and the Colorado River BasinExisting Research BasisCurrent Research GoalEstablishing Long Lead Climate/Streamflow

teleconnectionsDevelop Weighted Forecasting Method

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Climate Variability

Linkages of Colorado River basin hydrology with: Interannual climate variability (2-7 years)

El Niño - Southern Oscillation (ENSO)Northern Atlantic Oscillation (NAO)Pacific Ocean Sea Surface Temperatures (SSTs)

Interdecadal climate variability (10-20 years)Atlantic Multidecadal Oscillation (AMO)Pacific Decadal Oscillation (PDO)

Motivation: Improved long range(6-24 months in advance) streamflow forecasting 3

Climate Indices - Streamflow

Timilsena, Piechota, Tootle, & Singh, 2009

Pacific Ocean SST - Streamflow

Tootle & Piechota, 2005

Pacific Ocean SST - Snowpack

Aziz, Tootle, Piechota, Gray, 2009

(+)(-)

(-)

(-)(+)

Research Project Goal

Improve the “Out-Year” inputs used by USBRIdentify long-lead climate-streamflow connectionsDevelop weighted forecast approach

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ESPOUTLOOKESP

3-MONTH

APR-JUL COORDINATED

USBR INTERPOLATION

1976-2005 AVERAGE

Research Project Goal

Improve the “Out-Year” inputs used by USBRIdentify long-lead climate-streamflow connectionsDevelop weighted forecast approach

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Analysis

Lagged Rank Sum Testing SOI, PDO, NAO, AMOIndividually and ENSO-Coupled

Lagged Singular Value Decompostion (SVD)Pacific Ocean SSTs

Generate weighted forecasts and compare with:30-Year AverageESP Outlook

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Identify the Strongest Lag

Rank Sum Test Results

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Developing SST Teleconnection

Singular Value Decompostition (SVD) - Identifies covariance between two datasets

Pacific Ocean Sea Surface Temperature Data

(1951 – 2003)

CRB Naturalized/Unimpaired Streamflow Data

(1952 – 2004)

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3-Month SST Avg SVD Results

Why This Region?

Yang et al. 2002:Change in SST is evidence of a strong/weak

wintertime jet stream

Why the 1-year lag? Anybody want a Masters degree? 14

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Forecasting With SST Index

Forecast created using a weighted resampling of the observed data (1976-2005)Four Different Weighting Formulas

3-Month Avg. SST intervals: DJF, JFM, FMAPredictands: April-July Volume, Yearly Volume

0 5 10 15 20 25 30 350.000.100.200.300.400.500.600.700.800.901.00

W1 W2 W3 W4

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Assessing Forecast Skill

Linear Error in Probability Space (LEPS) scoreCompares forecast to the observed mean

Probability of Observed values compared with probability of Forecasted values:

2 23(1 | | ) 1f o f f o vLEPS P P P P P P

Qf

QO

Pf

PO

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Skill Results (DJF | Lag 1 year)

30-yr average skill scores at each location

(PRELIMINARY)

Conclusions

Improvement to the 30-Year Avg using HondoRemaining Work:

Quantify Improvement to the ESP Outlook

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