Temporal variability and spatial distribution of … · Teodoru C.R., Borges, A.V., Nyoni, F.,...

2nd International Conference on the Status and Future of the

World‘s Large Rivers

21-25 July, 2014 Manaus, Amazon, Brazil

Teodoru C.R., Borges, A.V., Nyoni, F., Nyambe, I., Darchambeau, F., & Bouillon, S.

Teodoru, C.R.1,

Borges, A.V.2, Nyoni, F.3, Nyambe, I.(3), Darchambeau F.2 & Bouillon, S.1

1 K.U. Leuven, Department of Earth and Environmental Sciences, Leuven, Belgium

2 University of Liège, Chemical Oceanography Unit, Liège, Belgium

3 University of Zambia, IWRM Centre, Lusaka, Zambia

Temporal variability and spatial distribution of suspended matter and organic C pool

in the Zambezi River system

AFRIVAL Project (African River Basins)http://ees.kuleuven.be/project/afrival/





The Zambezi River Basin – general characteristics

• 4th largest in Africa and the largest flowing in to the Indian Ocean (from Africa)

• Total length: > 3000 km; Drainage basin: ~ 1.4 x 106 km2 (shared by 8 countries)

• Main tributaries: Kabompo (270 m3/s), Luangina (65 m3/s), Kwando (53 m3/s),

Gwayi (85 m3/s), Kafue (370 m3/s), Luangwa (520 m3/s), Shire (115 m3/s)

• 2 main reservoirs: Kariba (5600 km2; 180 km3), and Cahora Bassa (2600 km2; 50

km3)

Kariba Res.

Cahora Bassa Res.

Victoria Falls Zambezi Delta

Zambezi source

BarotseFloodplains

Foto: Patrick

Wagner

LUKANGA





The Zambezi River Basin – climate and rainfall

• Climate is classified as humid subtropical or tropical wet and dry

• Annual rainfall varies with latitude: 1400 mm in N to 400-500 mm in S (mean

average rainfall for entire basin: 940 mm)

• Two seasons:

1. Wet season (Oct/Nov – Apr) corresponding to summer, with 95% of annual rainfall

2. Dry season (May – Sep/Oct), corresponding to winter, with 5% of annual rainfall

• Temperature across basin varies with elevation and, and less with latitude

• Mean monthly t°: 13°C for higher elevation in S to 23°C in E (July); and 23°C -

31°C (Oct)

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Jul

0

50

100

150

200

250

Dry Season

May-Sep

(40 mm)

Month

ly P

recip

ita

tion [

mm

]

Wet Season

Oct-Apr

(900 mm)





The Zambezi River Basin – hydrological cycle

• Driven by seasonality in rainfall patterns, hydrological cycle of the basin has a

bimodal distribution with a single main peak flood (max. Q: Apr/May) and min.

flow in Oct/Nov

• Due to regional rainfall distribution, northern tributaries contribute much more

water than southern ones

• Average annual discharge at Zambezi Delta: 3500-4000 m3 s-1

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1000

2000

3000

4000

5000

6000

7000

8000

2010-2011

Wet Season

Dis

cha

rge

[m

3 s

-1]

Date [mm/dd/yy]

Victoria Falls

Kariba DamDry Season

2011-2012 2012-2013





Sampling Strategy

• 3 campaigns: Wet (Feb-Apr) 2012, Wet (Jan-Apr) 2013, Dry (Oct-Dec) 2013

• 56 sites: 26 along Zambezi (Kariba & CB Res.), and 30 on tributaries (ITT Res.)

• 2 monitoring stations (Feb 2012 – Dec 2013):

ZBZ.11 ~ 5 km upstream the confluence with Kafue

KAF.10 ~ 6 km upstream the confluence with Zambezi

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7000

8000

2010-2011

Wet Season

Dis

cha

rge [

m3 s

-1]

Date [mm/dd/yy]

Victoria Falls

Kariba DamDry Season

biweekly monitoring: Zambezi and Kafue

Wet 2012

Dry

20

13

2011-2012 2012-2013

Wet 2013





Measured parameters

• Physico-chemical: pH, O2, t°, conductivity, Total Alkalinity

• Total Suspended Matter (TSM) and sediment characterization

• Concentration and stable isotope (δ13C and δ15N) composition

of POC, PN, DOC, DIC

• Aquatic metabolism: community respiration, primary production

• GHG (CO2, CH4, N2O) concentrations and fluxes

Headspace Technique Membrane Equilibrator Floating chamber

In-situ CO2 concentrations Fluxes





TSM – spatio-temporal dynamics

0 200 400 600 800 1000 1200 1400 1600

1

10

100

1000

Lukanga Swamps

ITT Res. (2012 wet)

ITT Res. (2013 wet)

ITT Res. (2013 dry)

TS

M -

Ka

fue

Riv

er

[mg L

-1]

Distance from source [km]

Kafue (2012 wet) Kafue (2013 wet)

Kafue (2013 dry)

Kafue Flats

0 500 1000 1500 2000 2500 3000

1

10

100

1000

Barotse Floodplains

C.B. Res. (2012 wet)


Kariba Res. (2012 wet)


Kariba Res. (2013 dry)

ZBZ (2012 wet)

ZBZ (2013 wet) ZBZ (2013 dry)

TS

M -

Zam

be

zi R

iver

[mg L

-1]


Shire River

(6-11 mg L-1)

Zambezi River Kafue River

Wet 2012 Wet 2013 Dry 2013 D Wet 2012 Wet 2013 Dry 2013

1

10

100

1000

Zambezi Kafue

p>0.093

p>0.293

TS

M [

mg L

-1]

p>0.109

p>0.912

NO interannual variability

NO distinct seasonality





TSM – spatio-temporal dynamics

0 200 400 600 800 1000 1200 1400 1600

1

10

100

1000

Lukanga Swamps

ITT Res. (2012 wet)

ITT Res. (2013 wet)

ITT Res. (2013 dry)

TS

M -

Ka

fue

Riv

er

[mg L

-1]



Kafue (2013 dry)

Kafue Flats

0 500 1000 1500 2000 2500 3000

1

10

100

1000

Barotse Floodplains





Kariba Res. (2013 dry)

ZBZ (2012 wet)

ZBZ (2013 wet) ZBZ (2013 dry)

TS

M -

Zam

be

zi R

iver

[mg L

-1]


Shire River

(6-11 mg L-1)


Zambe

ziKar

iba

Res

.C

.B. R

es.

Kabom

po

Kafue

ITT R

es.

Lung

aLu

angw

aLu

nsem

fwa

Maz

oe

Shire

1

10

100

1000

TS

M r

an

ge

[m

g L

-1]

Wet 2012 Wet 2013 Dry 2013 D Wet 2012 Wet 2013 Dry 2013

1

10

100

1000

Zambezi Kafue

p>0.093

p>0.293

TS

M [

mg L

-1]

p>0.109

p>0.912

NO interannual variability

NO distinct seasonality





POC, PN, δ13CPOC, C:N ratio

1 10 100 10000.1

1

10

100

% P

N [

%]

TSM [mg L-1]

1 10 100 10000.1

1

10

100

ITT Res.

Lunga

Luangwa

Lunsemfwa

Mazoe

Shire

Zambezi

Kariba Res.

C.B. Res.

Kabompo

Kafue

% P

OC

[%

]

-33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -180.1

1

10

100

Lunga

Luangwa

Lunsemfwa

Mazoe

Shire

Zambezi

Kariba Res.

C.B. Res

Kabompo

Kafue

ITT Res.

Perc

ent

PO

C [

%]

δ13

CPOC

[‰]

-33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -182

4

6

8

10

12

14

16

18

20

22 Kafue

ITT Res. Lunga

Luangwa

Lunsemfwa

Mazoe

Shire

Zambezi Kariba res.

C.B. Res. Kabompo

Mo

lar

C:N

ratio

δ13

CPOC

[‰]

POC - predominantly terrestrial (C3) origin:

Luangwa – more towards C4 soil C;

Reservoirs – fraction from phytoplankton

production





DOC– spatio-temporal dynamics


0 500 1000 1500 2000 2500 30000.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Shire River

C.B. Res. (2012 wet) C.B. Res. (2013 wet)



Kariba res. (2013 dry)

ZBZ (2012 wet)

ZBZ (2013 wet)

ZBZ (2013 dry)

DO

C -

Za

mb

ezi R

ive

r [m

g L

-1]


Barotse Floodplains

0 200 400 600 800 1000 1200 1400 16000.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Kafue Flats

Lukanga Swamps

ITT Res. (2012 wet)

ITT Res. (2013 wet) ITT Res. (2013 dry)

DO

C -

Kafu

e R

iver

[mg

L-1]



Kafue (2013 dry)

Zambe

ziKar

iba

Res

.C

.B. R

es.

Kabom

po

Kafue

I.T.T

. Res

.

Lung

aLu

angw

aLu

nsem

fwa

Maz

oe

Shire

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Ran

ge

DO

C [

mg L

-1]

Wet 2012 Wet 2013 Dry 2013 G1 Wet 2012 Wet 2013 Dry 20130.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

DO

C [

mg

L-1]

Zambezi Kafue

p>0.002

p>0.018

p>0.258

p>0.019

Distinct seasonality





DOC isotopic signature (δ13CDOC), and Age (∆14CPOC, ∆14CDOC)

-32 -30 -28 -26 -24 -22 -20 -18

-32

-30

-28

-26

-24

-22

-20

-18

Lunga

Luangwa

Lunsemfwa

Mazoe

Shire

Zambezi

Kariba Res.

C.B. Res.

Kabompo

Kafue

I.T.T. Res.

δ1

3C

DO

C [

‰]

δ13

CPOC

[‰]

1:1

0 1000 2000 3000-20

-10

0

10

20

30

40

50

60

70

80


∆14C

PO

C [

‰]

20

30

40

50

60

70

80

90

100

110

120 Zambezi (∆

14C

DOC)

Reservoirs (∆14

CDOC

)

Tributaries (∆14

CDOC

)

Zambezi (∆14

CPOC

)

Reservoirs (∆14

CPOC

)

Tributaries (∆14

CPOC

)

∆1

4C

DO

C [

‰]

0 500 1000 1500 2000 2500 3000

-28

-26

-24

-22

-20

-18

1.0 2.0 3.0 4.0 5.0 6.0

-28

-26

-24

-22

-20

-18


δ13C

DO

C [

‰]

Zambezi

Reservoirs

δ1

3C

DO

C [

‰]

DOC [mg L-1]

r2 = 0.5

DOC – mostly C3 origin with minimal

in-stream autochthonous production

δ13CDOC: δ13POC – decupling

between DOC and POC sources

∆14C – modern nature of riverine

organic C pool





Carbon Mass Balance

Area Q TSM POC DOC DIC CO2 CH4 C Yield GHG C Deposition C Export

[km2] [m3 s-1] [kt C yr-1]

Zambezi at Delta 11445 3779 9558 306 263 3672 2681 46.1 7163 2727 196 4240

Kafue at M.S. 658 314 196 8 45 205 459 4.6 738 464 16 258

Zambezi at M.S. 6403 1237 282 34 99 398 385 20.2 1042 391 120 531

Zambezi + Kafue =>

Zambezi & Kafue =>at monitoring stations (M.S.)





Thank you for your attention!

“Pirates of the Zambezi”

Temporal variability and spatial distribution of … · Teodoru C.R., Borges, A.V., Nyoni, F.,...

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