Science - USA (2022-02-18)

SCIENCEscience.org 18 FEBRUARY 2022¥VOL 375 ISSUE 6582 757

40

60

80

100

120

Installed

capacity (GW)

0.4

0.45

0.5

0.55

River

connectivity

150

250

350

450

550

Sediment

transport (Tg year -1)

3500

4000

4500

5000

5500

6000

Fish diversity

threat

500

1000

1500

2000

2500

3000

3500

Degree of

regulation

2000

3000

4000

5000

6000

GHG emissions

(Tg CO 2 eqyear )-1

Frequency in

optimal solutions

0.0 - 0.2

0.2 - 0.4

0.4 - 0.6

0.6 - 0.8

0.8 - 1 .0

0.00

0.25

0.50

0.75

1.00

0 100 200 300

Rank of dam

Maximum minus

minimum frequency

River connectivity Sediment transport Degree of regulation

Fish diversity threat GHG emissions

A

B C

D

0 100 200 300

Rank of dam

0.0

0.2

0.4

0.6

0.8

1.0

Frequency

Energy and

connectivity

0 100 200 300

Rank of dam

0.0

0.2

0.4

0.6

0.8

1.0

Frequency

Energy and

sediments

0 100 200 300

Rank of dam

0.0

0.2

0.4

0.6

0.8

1.0

Frequency

Energy and

five criteria

50 75 100 125

100

200

300

400

500

Sediment transport

(Tg year

–1)

River connectivity

Sediment

Sediment transport

(Tg year

–1)

Sediment transport

(Tg year

–1)

Sediment transport

(Tg year

–1)

50 75 100 125

100

200

300

400

500

Degree of regulation

Sediment

50 75 100 125

100

200

300

400

500

Fish diversity

threat

Sediment

50 75 100 125

Installed capacity (GW)

100

200

300

400

500

GHG emissions

Sediment

Fig. 3. The importance of choice of criteria for strategic hydropower
planning.(A) Rank frequency plots showing the frequency with which each of
the 351 proposed Amazon dams appears in optimal solutions for trade-off
analyses between energy and river network connectivity, sediment transport,
and all five environmental criteria considered simultaneously; dams in the
middle and right-hand plots are colored according to their frequency in
optimal solutions (purple, high frequency; yellow, low frequency) compared
with when only energy and connectivity are analyzed (left-hand plot), and
dot sizes are proportional to installed capacity. Note that as more objectives
are considered, fewer dams are in Pareto-optimal solutions owing to trade-
offs among criteria. (B) Maps showing the frequency with which each dam
appears in optimal solutions for each environmental criterion when criteria

are optimized individually; the bottom-right plot shows the difference between

the maximum and minimum frequencies in optimal solutions among the

five criteria for each dam, with the 351 dams ranked from highest to lowest

values. (C) Basin-wide sediment transport outcomes of Amazon dam

portfolios planned optimally to minimize sediment retention in comparison to

sediment outcomes attained when optimizing individually for each of the

other four criteria (river connectivity, degree of regulation, fish diversity, and

greenhouse gases). (D) Parallel coordinate plot with solutions that are Pareto-

optimal for all criteria simultaneously. Each coordinate corresponds to a

criterion, and each line connecting different values along the coordinates

corresponds to a single Pareto-optimal solution; all optimal solutions for 80 ±

0.5 GW are highlighted in orange. GHG, greenhouse gas emissions.

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