Mid-Range Streamflow Forecasts for River Management in the Puget Sound Region Richard Palmer Matthew...

Mid-Range Streamflow Forecasts for River Management in the Puget Sound Region

Richard Palmer

Matthew WileyDepartment of Civil and Environmental Engineering

March 21, 2005

Outline Region’s Water Supply Basins

Models Current Conditions

Forecast Methods ESP, Extended Streamflow Prediction CPC, Climate Predication Center

Current Forecasts

Water Snowpack Modeling

Streamflow Forecasts

Impacts on Storage

Special Thanks to the Water Forum for Funding the Mid-

Range Forecasts

Hydrologic Model - DHSVM Physically based, distributed model Calculates energy and water balance

at the grid cell level 150 meter resolution, 3hr time-step Station based meteorology Output streamflows are aggregated

to monthly total volume Recently incorporated an

experimental groundwater component

Sultan River Snohomish PUD

Hydropower project Everett Water Supply

S.F. Tolt River Seattle Water Supply

Cedar River Seattle Water Supply

Green River Flood Control Tacoma Water Supply

All have environmental flow requirements

Streamflow Forecasts Initialize basin models to current conditions using recent observed meteorology ESP (Extended Streamflow Prediction)

Project 13 months into the future using each year in the historic record as one of many possible scenarios (traces).

Forecast can be conditioned using subsets of years based on observed climatologically conditions, such as ENSO state

CPC (Climate Prediction Center) Seasonal outlooks of the probability of deviations from normal

temperature and precipitation for 13 months Each season's outlook and probability that a temperature or

precipitation quantity will be exceeded for a climate region at the given lead time of two weeks to a year.

Modeling Snowpack

DHSVM allows evaluation of snowpack conditions over time

Provides graphical presentation of basin state Estimate of total water storage as snow Essential for evaluating the future based on

current conditions Provide spatial information to complement

Snotel and Snow Course information

March 1 Snow Conditions in Seattle Water Supply Basins

0.04

0.43

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.25 0.5 0.75 1non-exceedance probability

we

igh

ted

av

era

ge

sw

e

de

pth

(m

ete

rs)

Simulated Historic (1928-2004)20051950

Year

Average SWE (meters)

Snow Storage (KAF)

Billions of Gallons

1950 0.43 189 622004 0.19 83 271977 0.03 15 5

1941/2005 0.04 16 5


0.04

0.19

0

0.1

0.2

0.3

0.4

0.5

0.6


we

igh

ted

av

era

ge

sw

e

de

pth

(m

ete

rs)


Year


Snow Storage (KAF)

Billions of Gallons

1950 0.43 189 622004 0.19 83 271977 0.03 15 5

1941/2005 0.04 16 5


0.040.030

0.1

0.2

0.3

0.4

0.5

0.6


we

igh

ted

av

era

ge

sw

e

de

pth

(m

ete

rs)


Year


Snow Storage (KAF)

Billions of Gallons

1950 0.43 189 622004 0.19 83 271977 0.03 15 5

1941/2005 0.04 16 5


0.040.040

0.1

0.2

0.3

0.4

0.5

0.6


we

igh

ted

av

era

ge

sw

e

de

pth

(m

ete

rs)


Year


Snow Storage (KAF)

Billions of Gallons

1950 0.43 189 622004 0.19 83 271977 0.03 15 5

1941/2005 0.04 16 5

Forecasts Results USGS 12137290 SULTAN1: Inflow to Spada

USGS 12147600 TOLT1: Inflow to SFT TOLT2: Below SFT

USGS 12115000 USGS 12117000 CEDAR1: Inflow to CM CEDAR2: Below CM

HH_INFLOW: Inflow to Howard Hansen

Cedar River above Chester Morse Reservoir

Historic probability of forecast value, MAMJJA reservoir inflows

6%

0

100

200

300

400

500

600

700

800

900

1000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Non-exceedence probability

Cu

mu

lati

ve

Infl

ow

s (

KA

F)

12115000

WY2005

S.F.Tolt River above S.F.Tolt Reservoir


4%

0

20

40

60

80

100

120

140

160

180

200

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1


Cu

mu

lati

ve

Infl

ow

s (

KA

F) 12147600

WY2005

Green River into Howard Hansen Reservoir


11%

0

500

1000

1500

2000

2500

3000

3500

4000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1


Cu

mu

lati

ve

Infl

ow

s (

KA

F) HH_Inflow

WY2005

All Inflows into Spada Reservoir


22%

0

500

1000

1500

2000

2500

3000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1


Cu

mu

lati

ve

Infl

ow

s (

KA

F) SULTAN1

WY2005

Implications to Water Supplies Factors to Consider

Current storage Inflows to reservoirs Inflows below reservoirs that contribute to fish

requirements Average demand and effect of conservation Availability of supplemental groundwater supplies “Normal” versus “Low” versus “Critical” instream flows

Examined Seattle and Tacoma systems

Potential System Storage Forecast

0

5

10

15

20

25

30

35

40

10/1

/200

4

11/1

/200

4

12/1

/200

4

1/1/

2005

2/1/

2005

3/1/

2005

4/1/

2005

5/1/

2005

6/1/

2005

7/1/

2005

8/1/

2005

9/1/

2005

Bill

ion

s o

f G

allo

ns

Historic Maximum

Historic Minimum

Historic Average

Initial Condition

FC_avg

Implications for Puget Sound Water Supply Systems Inflows to reservoirs expected to be only 40% to

50% of average, slightly higher in the Everett system.

60% chance of the Seattle system not completely refilling this spring ( ~32 billion gal.)

10% chance of the Tacoma system not completely refilling this spring (~10 billion gal.)

If NO action is taken: (i.e. “Normal fish flows, average demand) 10%-15% of shortfall by October.

Implications for Puget Sound Water Supply Systems A 10% reduction in consumption reduces

probability to around 5% chance of shortfall Current snowpack is only half of the picture,

spring rains can also refill reservoirs 10-12 inches* (at Seatac) between March 1 and

July 1 will get us to near average storage by September 1 *(Average precip is 9.5

inches)

In an average year there is a considerable “surplus” of water in the basins

Implications for Puget Sound Water Supply Systems Actions have already being taken Actual operations are very dynamic with

considerable flexibility and continual adjustments based on evolving conditions

Minimizing ecological damage and preventing disruptions to customers are primary goals

A “serious” situation requires several events (low snow pack, below average summer flows, late return of rain)

Questions ?

CPC forecast: MAM

CPC forecast: MJJ

CPC forecast: JJA

CPC forecast: JAS

CPC forecast: ASO

CPC forecast: SON

Taylor Creek below Chester Morse Reservoir

S.F.Sultan River above Spada Reservoir

Green River into Howard Hansen Reservoir

Mid-Range Streamflow Forecasts for River Management in the Puget Sound Region Richard Palmer Matthew...

Documents

Transcript of Mid-Range Streamflow Forecasts for River Management in the Puget Sound Region Richard Palmer Matthew...