Climate Informed Decision Tools for a Multi-use Reservoir:

The case of Angat and Manila, Philippines

Casey Brown, Sankar Arumugam and Upmanu Lall

The International Research Institute for Climate and Society and

Columbia University

Outline

•Climate and Water Resources Risk in Manila

•Decision Tool for Water Allocation – using seasonal forecast

•Dry-year Option Contracts

•Conclusion – Climate Risk Management for Water Managers–Building Resilience Systems

Northeast Monsoon (Oct – Dec)

Inflow to Angat Reservoir

0

50

100

150

200

250

300

350

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Stre

amflo

w (i

n hm

3)

0

50

100

150

200

250

300

350

400

450

500

Rai

nfal

l (m

m)

StreamflowRainfall

3-months lag correlation

ρ(Nino3.4,QJJAS) = -0.20

ρ(Nino3.4,QOND) = -0.51

JJAS – 30%

OND – 46%

Seasonal Climate Forecast

Angat Reservoir – Manila Water Supply

A aerial view of the Angat Hydroelectric Plant

Courtesy of Mr. Rodolfo German (Angat dam)

Reservoir ManagementHydropower

Water Delivery

Storage

SpillForecast

of Inflows

0

1020

3040

50

6070

8090

100

1 2 3 4 5 6 7 8 9 10 11 12

Critical Months for Water Management

0

1

2

3

4

5

6

7

8

9

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Months

Num

ber o

f yea

rs o

f Spi

lls

Number of years of spills

Angat Decision RuleANGAT H.E. PLANT

150

160

170

180

190

200

210

220

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

ELEV

ATI

ON

(m)

1996 1997 1998 1999 2000 2001 UPPER LOWER

0

1020

3040

50

6070

8090

100

1 2 3 4 5 6 7 8 9 10 11 12

Dynamic Rule Curve

Inflow

Flood

Dry Forecast

0

10

2030

40

50

60

7080

90

100

1 2 3 4 5 6

Less Inflow

Less Flood Risk

More Storage Possible

0102030405060708090

100

1 2 3 4 5 6

More Inflow

Greater Flood Risk

More Release Possible

Wet Forecast

Decision Tool for Water Management

Seasonal Inflow Forecast

Increased Hydropower

0

200

400

600

800

1000

1200

1400

1987 1989 1991 1993 1995 1997 1999 2001

Year

Hyd

ropo

wer

Gen

erat

ed (

in G

WH

)

0

50

100

150

200

250

300

350

400

Observed In

flow

ActualUpdated ForecastOctober ForecastObserved

Irrigation Improvement

0

50

100

150

200

250

1987 1989 1991 1993 1994 1997Year

Allo

cati

on f

or I

rrig

atio

n (

in h

m3

) DecemberNovemberOctober

Current Reservoir Contents

Remaining Water:Agriculture and Hydropower

First Priority: Manila Water

Urban Centers

Low Inflow

“Business as Usual”

Current ReservoirContents

Probabilistic Inflow Forecast

Dry Year Option Contracts

Contractsw/

Dry Year Option

• Building Resilience Systems– Seasonal Climate forecasts

• Early Warnings of Drought, Flood– Decision Support– Economic mechanisms

• Dry year option/insurance

• Better outcomes– Maximize the “good” years– Reduce risk exposure in dry years

Climate Risk Management for Water Managers

Thank You!

•• Thank you!Thank you!