Water Supply Seasonal Volume Forecasts

(TDAO3) COLUMBIA - THE DALLES DAM

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The Official Statistical Water Supply forecast is issued between the middle of December and July 1st. Ensemble Predicted forecast are issued weekly.   A comparison continues to be made between the two forecasts through the end of September.

COLUMBIA - THE DALLES DAM (TDAO3) Forecasts for WY 2009
Official Forecast (Regression)   Issued: 2009-03-06      {Description}									ESP Forecasts   Issued: 2009-03-09
Period	Forecast (KAF)	% of Average	5% Forecast	95% Forecast	30yr (1971-2000) Average	Max of Record	Min of Record		Forecast Period	ESP Forecasts for Forecast Period (KAF)					Obs Flow From Start of Period To 3/9/2009
										90 % Exceedance Probability	70 % Exceedance Probability	50 % Exceedance Probability	30 % Exceedance Probability	10 % Exceedance Probability
JAN-SEP	97400.0	80	115034.0	79766.0	121300.0	176593.0	64517.0		JAN-SEP	89163.0	94279.2	98997.9	100588.3	106964.4	12187.0
MAR-SEP	87000.0	80	104634.0	69366.0	108200.0				MAR-SEP	78737.0	83853.2	88571.9	90162.3	96538.4	1761.0
APR-AUG	74800.0	80	92434.0	57166.0	93090.0	133733.0	49445.0		APR-AUG	68308.2	72984.3	76145.1	78648.5	84297.7	0.0
JAN-AUG	92900.0	80	110534.0	75266.0	115700.0	168669.0	59871.0		JAN-AUG	84881.2	89526.7	92670.0	95375.6	101761.5	12187.0
MAR-AUG	82500.0	80	100134.0	64866.0	102700.0				MAR-AUG	74455.2	79100.7	82244.0	84949.6	91335.5	1761.0
APR-SEP	79300.0	80	96934.0	61666.0	98650.0	141056.0	54091.0		APR-SEP	72590.0	77904.0	82488.6	83608.0	89825.5	0.0
JAN-JUL	86200.0	80	103834.0	68566.0	107300.0	159000.0	53359.0		JAN-JUL	78333.3	82927.7	86145.4	88014.7	94699.1	12187.0
MAR-JUL	75800.0	80	93434.0	58166.0	94230.0				MAR-JUL	67907.3	72501.7	75719.4	77588.7	84273.1	1761.0
APR-JUL	68100.0	80	85734.0	50466.0	84650.0	123463.0	42933.0		APR-JUL	61811.0	66217.9	68993.6	71206.3	77174.1	0.0

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Forecast Statistical Information

January - July Forecast     86.2 MAF   80% of (1971-2000) average

Historical January-July Volumes in MAF    Mean: 107   Min: 53   Max: 159

Year Jan-Jul Vol (MAF) Rank Exceedance Prob 1989 93.02 33 67.347 % 1993 90.82 34 69.388 % 1985 90.33 35 71.429 % 1966 89.73 36 73.469 % 2003 87.69 37 75.510 % 2009 86.20 38 77.551 % 1979 83.03 39 79.592 % 2004 82.96 40 81.633 % 2005 81.35 41 83.673 % 1987 78.64 42 85.714 % 1994 76.40 43 87.755 % Rankings and probabilities based on historical water years 1961 to 2009 Click for full ranking list of all years

Contingency Forecast (MAF) Date Type 50% 75% 100% 125% 2009-01-01 Early Bird 54 71 92 116 2009-01-01 Final 54 - 94 116 2009-01-01 Mid Month 65 79 95 80 2009-02-01 Early Bird 64 78 93 110 2009-02-01 Final 64 77 92 109 2009-02-01 Mid Month 60 72 84 99 2009-03-01 Early Bird 64 74 84 95 2009-03-01 Final 66 75 86 97

NWRFC ESP Summary Plots

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US Dept of Commerce National Oceanic and Atmospheric Administration National Weather Service Northwest River Forecast Center (NWRFC) 5241 NE 122nd Avenue Portland, Oregon 97230-1089 Telephone: 503-326-7401 Last Modified: March 16, 2009

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