View
217
Download
0
Embed Size (px)
Citation preview
Recap of Water Year 2007 Hydrologic Forecast and Forecasts for Water Year 2008
Alan F. Hamlet Andrew W. Wood Dennis P. Lettenmaier
•JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering
University of Washington
5000
10000
15000
20000
25000
30000
-3 -2 -1 0 1 2 3 4
Nino 3.4 Anomaly (C)
Apr
il-S
epte
mbe
r A
vg N
atur
aliz
ed
Str
eam
flow
(cf
s)
Natural Flows at Milner 1928-1989
Milner2007Nino3.4 Range0.7 to 1.5
Nat
ural
Flo
w (
KA
F)
Red = long term meanBlue = ensemble meanGray = ensemble membersBlack = range of observations
2007 Forecast for Natural Flow at Milner
Milner2007Nino3.4 Range0.7 to 1.5Warm PDO
Nat
ural
Flo
w (
KA
F)
Red = long term meanBlue = ensemble meanGray = ensemble membersBlack = range of observations
2007 Forecast for Natural Flow at Milner
Upp
er S
nake
Sto
rage
(K
AF
)
Upp
er S
nake
Sto
rage
(K
AF
)
2007 System Storage Forecasts for the Upper Snake (Oct-Aug)
Nino3.4 Range0.7 to 1.5
Nino3.4 RangeWarm PDO
FullFull
Obs. Storage 9/30/07 (423.8 KAF)
http://www.ecmwf.int/products/forecasts/d/charts/seasonal/forecast/seasonal_range_forecast/nino_plumes_public_s3!3.4!200709!/
150000
200000
250000
300000
350000
400000
450000
-3 -2 -1 0 1 2 3 4
NINO3.4 Index Anomaly
Ap
ril-
Se
pte
mb
er
Av
era
ge
S
tre
am
flo
w
1916-2002
April-September Naturalized Flow for the Columbia River at The Dalles, OR from Historic Water Years vs January Nino 3.4 Anomalies.
5000
10000
15000
20000
25000
30000
-3 -2 -1 0 1 2 3 4
Nino 3.4 Anomaly (C)
Apr
il-S
epte
mbe
r A
vg N
atur
aliz
ed
Str
eam
flow
(cf
s)
Natural Flows at Milner 1928-1989
Mod
ified
Str
eam
flow
(cf
s)
Bias-Adjusted West Wide Forecast at The Dalles (1961-2000)
The Dalles
Red = long term meanBlue = ensemble meanGray = ensemble membersBlack = range of observations
Nat
ural
Flo
w (
KA
F)
Red = long term meanBlue = ensemble meanGray = ensemble membersBlack = range of observations
Simulated Natural Flow at Milner (ESP all years)
Milner
Nat
ural
Flo
w (
KA
F)
Red = long term meanBlue = ensemble meanGray = ensemble membersBlack = range of observations
Simulated Natural Flow at Milner (ESP cool ENSO)
Milner
Conclusions:
•The WY 2007 ESP forecast predicted increased likelihood of drought. Observed summer flows at Milner in 2007 were strongly below average (~55% of normal for April-Sept) and were towards the bottom of the ensemble.
•A moderate to strong cool ENSO event is expected for the winter of 2007-2008, which historically is associated with increased likelihood of above average Apr-Sep flow at Milner.
•Dry initial soil conditions in the basin are projected to systematically reduce natural flows at Milner from April-Sept for water year 2008. However even with dry soils, the forecast at Milner shows increased chance of high flows. Snakesim model simulations suggest increases in carry over storage in the upper Snake in Sept 2008 above about 1.0 MAF.
1904 1.47
1907 1.00
1921 1.00
1925 0.49
1932 0.39
1943 0.88
1965 0.90
1971 1.55
1974 2.22
1984 0.58
1989 -0.40
1996 0.93
1999 0.89
Historic Dalles Apr-Sept streamflow anomalies for water years with previous winter warm ENSO, current winter cool ENSO
Stats:
12 of 13 above 0.39
11 of 13 above 0.49
9 of 13 above 0.88
WY Std Ann.
1932 -0.235
1943 1.137
1965 1.238
1971 2.170
1974 1.686
1984 1.883
1989 -0.080
Historic Milner Apr-Sept streamflow anomalies for water years with previous winter warm ENSO, current winter cool ENSO
WY Std Ann.
Stats:
5 of 7 above 1.1
3 of 7 above 1.7