1

Impactos da barragem de Alqueva no ecossistema do estuário do Guadiana e nas pescas na zona costeira adjacente: necessidade de uma gestão ecohidrológica

Luis Chicharo*, Maria Alexandra Chícharo, Radhoune Ben-Hamadou, Ana Amaral, Pedro Morais, Ana Faria

University of Algarve/CCMARlchichar@ualg.pt (*)

Structure of the presentation

1 – BRIEF CHARACTERIZATION OF THE GUADIANA SYSTEM

2 – SOME EXAMPLES OF EFFECTS OF THE ALQUEVA DAM ON THE

GUADIANA ESTUARY AND COASTAL ECOSYSTEMS

3 – BRIEF INTRODUCTION TO THE ECOHYDROLOGY (EH) CONCEPT

4 – EXAMPLES OF APPLYING THE EH CONCEPT IN THE GUADIANA ESTUARY

5 – CONCLUSIONS

2

The Facts about dams

Almost 80% of the surface of the Earth is modified by Man

>800 000 dams (2 large dams - >15 m) per day, in last 50 years (World Commission on Dams, 2000)

On-going and future climate changes will result in more dry areas and the need for more water storage

DAMS WILL CONTINUE TO BE BUILD

NEED TO CHARACTERIZE IMPACTS FOR THE SUSTAINABLE MANAGEMENT OF ESTUARINE AND COASTAL ECOSYSTEMS

N

N

4th largest river basin in the IberianPeninsula 67.500 km2

83% in Spain +17% in Portugal

1824 dams in the basin

The Guadiana basin

GUADIANA ESTUARY:

•RAMSAR Site

• National Park (Reserve)

• Special Protection Zone (ZPE)

• Important Bird Area (IBA)

3

Guadiana River discharge variability

High temporal variability in water availability for agriculture & human consumption(affecting the depressed Alentejo region)

ALQUEVA DAM CONSTRUCTION

High level of exploitation of groundwater resources (60% of total)

WITHOUT DAMS WITH DAMS

(Dias & Ferreira, 2001)

• The largest artificial lake in Europe –surface area: 250 km2

• Perimeter: more than 1.000 km

• Capacity : 4.150 hm3

• Provide water for 110.000 ha of intensive irrigation in a semi-arid region

• Constant supply of water to populations

• Generate hydroelectric power

MAJOR OBJECTIVES:

MAJOR CHARACTERISTICS:

The Alqueva Dam

Operating since March 2002

4

Ecological impacts on the river, estuary and coastal

zone

Impacts on social and economic activities

Water stored by the Alqueva Dam

(Dias & Ferreira, 2001)

Volume of water retained in the Guadiana river and not reaching the estuary and coastal area, with the Alqueva Dam operating since 2002

Aquaculture – may be affected by algal blooms, salinity changes and reduction of water oxygenation

Salt extraction – may be affected by degradation of water quality

Coastal fisheries – may be affected by the reduction of coastal productivity and limitation of fish species to use the estuary as nursery area

Tourism and recreational activities – may be affected by the degradation of water quality and eventual occurrence of toxic algal blooms

Economic relevant “water related” activities

5

Impacts of the Alqueva dam on the estuarine and coastal Guadiana ecosystems

Alqueva impact on estuarine salinity distribution

Longitudinal gradient of isohalines in the Guadiana estuary

Salinity average 2001 2002january 2,1 16,4may 15,7 24september 20 23,15

BEFORE AFTER

Salin

ityD

ista

nce

(km

)

Naturalvariability?

6

Alqueva impact on estuarine primary productivity

µg C

hla.

L-1

Oct96 Nov96 Dez96 Fev97 Mar97

µg C

hla.

L-1

BEFORE AFTER

Decrease in primary productivityBottom-up + top-down (bivalves) effect?

Unio spp.

indigenous species

Decrease in river discharge

Increase salinization in upper estuary

Increase of Corbicula abundance

Alqueva impact on bivalves distribution and abundance

Corbicula flumineaalien species

7

Alqueva impact on estuarine nursery functionETM

EGGS

JUVENILES ADULTS

LARVAE

RIVERDISCHARGE

Engraulis spp.

variação interanual: caudal medio e abundancia ovos

0

5000

10000

15000

20000

25000

30000

1987/89 1996/97 1999/00 2001/02 2002/03 2005/060

100

200

300

400

500ovos junhocaudal

Nºo

vos/

m3 BEFORE

AFTER

Caudal m

édio m3/s

variação interanual: caudal medio e abundancia ovos

0

5000

10000

15000

20000

25000

30000

1987/89 1996/97 1999/00 2001/02 2002/03 2005/060

100

200

300

400

500ovos junhocaudal

Nºo

vos/

m3 BEFORE

AFTER

Caudal m

édio m3/s

PLUME

SPAWNING AREA

Influencia do caudal na postura

R2 = 0,956

0

5000

10000

15000

20000

25000

30000

0 50 100 150 200 250 300 350 400 450 500

Caudal anual medio m3/s

Nºo

vos/

m3

Influencia do caudal na postura

R2 = 0,956

0

5000

10000

15000

20000

25000

30000

0 50 100 150 200 250 300 350 400 450 500

Caudal anual medio m3/s

Nºo

vos/

m3

Influência do caudal na densidade de ovos

Alqueva impact on fish larvae

Pom/Eng larvae ratioDecrease Engraulis spp. Increase Pomatochistus spp.

LOW & HIGH DISCHARGEMEDIUM DISCHARGE

1996/1997- 3,87 (caudal elevado)2002/2003 - 3 (caudal baixo)

1987/1988 -1,5 (caudal médio)

8

Alqueva impact on adult fish abundance in the Guadiana estuary

Species

Density

Species Density

2001 Feeding

group Ecological

guild Percentage

n?.m–2

2002 Percentage

n?.m–2

Engraulis encrasicolus (Ee) Planktiv Nursery 16.07% 0.10 Pm 29.44% 0.15Barbus sp. (Bsp) Omniv Freshwater 12.40% 0.08 Pmi 17.27% 0.09Barbus comiza (Bc) Omniv Freshwater 11.85% 0.07 Ee 10.63% 0.05Barbus sclateri (Bs) Omniv Freshwater 10.36% 0.07 Bs 9.69% 0.05Pomatoschistus minutus (Pm) Carniv Resident 9.45% 0.06 Bc 6.40% 0.03Halobatrachus didactylus (Hd) Carniv Resident 8.94% 0.06 Hd 4.45% 0.02Barbus microcephalus (Bm) Omniv Freshwater 5.24% 0.03 Psp 2.97% 0.01Pomatoschistus sp. (Psp) Carniv Resident 2.99% 0.02 Asp 2.37% 0.01Echiichthys vipera (Ev) Carniv Marine 2.41% 0.02 Dl 2.27% 0.01Dicentrarchus labrax (Dl) Carniv Nursery 2.11% 0.01 Ev 2.05% 0.01Diplodus bellotti? (Db?) Carniv Nursery 1.85% 0.01 Sl 1.55% 0.01Sarpa salpa (Ss) Planktiv Marine 1.71% 0.01 Aa 1.22% 0.01Solea vulgaris (Sv) Carniv Nursery 1.53% 0.01 Ds 1.04% 0.01Mullus surmulletus (Ms) Carniv Nursery 1.27% 0.01 Solea lascaris (Sl) Carniv Nursery 1.13% 0.01 Pomatoschistus microps (Pmi) Carniv Resident 1.12% 0.01 Gobius níger (Gn) Carniv Resident 0.87% 0.01 Diplodus sargus (Ds) Carniv Nursery Anguilla anguilla (Aa) Carniv Catadromous Argyrosomus regius Carniv Marine Liza ramada (Lr) Ominv Resident Cyprinus carpio (Cc) Carniv Freshwater Atherina spp. (Asp) Planktiv Resident

TOTAL 0.40 TOTAL 0.39

Species Av.Diss Diss/SD Contrib% Cum.% Engraulis encrasicolus 11.64 1.58 12.52 12.52 Pomatoschistus minutus 10.29 1.55 11.07 23.58 Barbus sclateri 8.57 1.65 9.21 32.79 Barbus comiza 7.42 0.55 7.98 40.77 Halobatrachus didactylus 6.93 1.53 7.45 48.23

BEFORE AFTER

Alqueva impact on coastal fisheries

0

500

1000

1500

2000

2500

3000

3500

4000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

0200400600800100012001400160018002000

Total Fish Landing Tonnes Y rigthInflow m3.s-1S.pilchardus Tonnes

BEFORE AFTER

Land

ings

(tonn

es)

Inflowm

3/s

Demersalcarnivorous

HIGH INFLOW LOW INFLOW

Planktivorous

9

Impact of river discharge on coastal fisheries and diversity

COASTAL FISH ASSEMBLAGE

R2 = 0,5021

70

75

80

85

90

0 200 400 600 800

INFLOW m3.s-1

DEL

TA*

COASTAL FISH ASSEMBLAGES COSTAL BIVALVE ASSEMBLAGE

R2 = 0,4735

70

75

80

85

90

95

100

0 200 400 600 800

INFLOW m3.s-1

DELT

A *

COASTAL BIVALVE ASSEMBLAGES

Medium discharge values increasesfishery catches and diversity

Low- Medium inflow condition

R2 = 0,6173

0

500

1000

1500

2000

2500

3000

0 100 200 300 400 500 600 700 800

Inflow (m3.s-1)

Tota

l Lan

ding

s (to

nnes

)

risk of biodiversity changes in the river, estuary and coastal area –due to changes in salinity spatial distribution and productivity

risk of loss of estuary spawning and nursery functions for species, some with economic importance – due to decrease in river plume

risk of changes in coastal fisheries – due to decrease in outwelling

risk of algal blooms and eutrophication – due to the modification of nutrients concentrations and ratios, increase in agricultural areas and in residence time

risk of saltmarsh degradation and coastal erosion – due to the change in sediment load grain size

Ecological risks at the Guadiana estuary and coastal area associated with the Alqueva Dam

10

The Ecohydrology approach for sustainablemanagement of ecosystems impacts

Goals for management and restoration of theGuadiana estuary and coastal area

Provide low-cost and long-term sustainable solutions for estuarine and coastal management

minimize threats (mostly caused by anthropogenic activities) for human health and biodiversity

maximize water availability and quality for ecosystem services and society uses

11

The Ecohydrology (EH) concept

ECOHYDROLOGY CONCEPT - Integrate hydrology and biology to achieve a sound understanding of ecosystems functioning and provide tools for the sustainable

management of water resources (EH PROGRAM, UNESCO IHP)

BIOLOGYHYDROLOGY

INDICATORDISTURBANCE

Water Framework Directive“good ecological status of water bodies”

Role of biota on hydrology???

“DUAL REGULATION”Hydrology regulates biota and shaping biota can regulate

hydrology

HARMONIZATIONof hydrotechnical infrastructure

INTEGRATIONof various regulations acting in a synergistic way to stabilize and improve the quality of

water resources

REGULATION

BIOTA

HYDROLOGY

Ecohydrology assumptions

12

HYDROLOGICALHydrological cycle in the basin

is a template for functional integration of hydrological and

biological processes

ECOLOGICALintegrated processes at river

basin and coastal ecosystems can be steered to increase the

carrying capacity and ecosystem services

Ecohydrology principles

ECOLOGICAL ENGINEERING

Regulation of hydrological and ecological processes is the basis for the design of integrated and sustainable solutions for water

ecosystems

Applying Ecohydrology to the Guadiana estuary

13

Case 1.Salt-marsh fringed Guadiana Estuary, Portugal – Spain

Case 2. Mangrove-fringed Darwin Harbour estuary, Australia.

An Ecohydrologic model for the Guadiana estuary

Wolanski et al, 2004

The Ecohydrology model validation

salinidade nitratozooplâncton

bivalvepeixes

RIVER SEA RIVER SEA

14

The Ecohydrology model results

No saltmarsh

Situation as is

No bivalves

river sea

Ex. Testing scenarios forcontrolling algal blooms

Corbicula

0

0,010,02

0,03

0,04

0,050,06

0,07

0 2 4 6 8

Tempo

Taxa

de

Inge

stão Bivalve 1

Bivalve 2Bivalve 3Bivalve 4

Unio

-0,002

0

0,002

0,004

0,006

0,008

0,01

0,012

0 2 4 6 8

Tempo

Taxa

de

inge

stão Bivalve 1

Bivalve 2Bivalve 3Bivalve 4

µg C

hl.a

/h/m

g

Time (hours)

Time (hours)

Corbicula fluminea

Unio sp.

µg C

hl.a

/h/m

g

Comparison of bivalves filtration rates

15

Model simulations: biota controls hydrology

Efficiency = 0.9

Efficiency = 0.7

Efficiency = 0.5

Efficiency = 0.3

Risk of algal bloomRisk of algal bloom

NO3

NH4

C. flumineam.C

Phytoplankton

LL

LL: Light Limitation,LL: Light Limitation,m.Cm.C: Corbicula mortality.: Corbicula mortality.

• Model based on azote exchange between variables

• Phytoplankton limited by azote supply

• Unit box model (0-D)

• Day/Night phytoplankton limitation

• Corbicula mortality to balance growth Constant biomass.

• Filtration rates based on 18mm length specimens

Top-down control

Hyd

rolo

gica

l osc

illat

ions

LOW STOCHASTICITY

HIGH STOCHASTICITY

Role of dams as a tool to increase stochastic hydrological processes and planktonic assemblages changes

Increase planktonicdiversity

“Exclusive competitionPrinciple”

(Hutchinson, 1961)

“Flow Pulse concept”(Roelke, 2003)

Hydrology regulates biota: effect of dam discharge

16

PHYTOPLANKTON ASSEMBLAGESPHYTOPLANKTON ASSEMBLAGES

ZOOPLANKTON ASSEMBLAGESZOOPLANKTON ASSEMBLAGES

“NATURAL”FRESHWATER

PULSE

Effects of freshwater pulse on planktonicassemblages

LL: Light Limitationm.D: Diatoms mortalitym.C: Cyanobacteria mortalitym.H: Herbivore mortality

Model conceptual scheme

Nitrogen

Phosphate

Diatoms

Cyanobacteria

LL

Silicate

Herbivore

FLOW DISCHARGE:FREQUENCY &

AMPLITUDE

m.D

m.C

m.H

Nitrogen

Phosphate

Diatoms

Cyanobacteria

LL

Silicate

Herbivore

FLOW DISCHARGE:FREQUENCY &

AMPLITUDE

m.D

m.C

m.H

17

Ecologic flow regulates plankton assemblages

AVERAGE 5 m3/s

FREQUENCY MORE EFFECTIVE THAN AMPLITUDE

Frequency vs. amplitude of the flow pulse

C

H

D

CH

D

DC

HD

CH

18

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8 9

Mar

-02

Apr

-02

May

-02

Jun-

02Ju

l-02

Aug

-02

Sep-

02O

ct-0

2N

ov-0

2D

ec-0

2Ja

n-03

Feb-

03

stations

caudal diário pulo do lobo 2002

0100200300400500600700

01/0

120

/01

08/0

227

/02

18/0

306

/04

25/0

414

/05

02/0

621

/06

10/0

729

/07

17/0

805

/09

24/0

913

/10

01/1

120

/11

09/1

228

/12

caud

al m

3 .s-1

April – anchovyspawning season

Temporal considerations for the flow pulse discharge

Inflow (Pulo do Lobo – 2002)

50 m3/s

FISH EGGS

“Flow pulse” and ecosystem functions

Qmax= 50 m3.s-1 (sudden end)

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10

Days

% o

f par

ticle

s in

est

uary

19

Impact of river discharge pristine degraded

DAM REGULATION OF ECOSYSTEM FUNCTIONS

Harmonization of dam with ecosystem functions

BIODIVERSITY

BIOMASS

Water storage upstream affect downstream ecosystems functionsand processes

Disruption of natural freshwater discharge variability caused changesin physico-chemical water parameters, caused a decrease in theestuarine productivity, changed biota assemblages in the estuaryand affected coastal fisheries

Increasing the number of dammed rivers requires integration ofnatural climatic variability with hydrotechnical infrastructure (ex. byregulating the amplitude and periodicity of freshwater discharges)

Ecohydrology approach, at the entire river basin, can provide good tools for preventing and reverting degradation of estuarine and coastal ecosystems

Conclusions

20

GRACIAS / OBRIGADO