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
2University 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
•
4
th
largest in Africa and the largest flowing in to the Indian Ocean (from Africa)
•
Total length: > 3000 km; Drainage basin: ~ 1.4 x 10
6
km
2
(shared by 8 countries)
•
Main tributaries: Kabompo (
270 m
3
/s
), Luangina (
65 m
3
/s
), Kwando (
53 m
3
/s
),
Gwayi (
85 m
3
/s
), Kafue (
370 m
3
/s
), Luangwa (
520 m
3
/s
), Shire (
115 m
3
/s
)
•
2 main reservoirs: Kariba (
5600 km
2
; 180 km
3
), and Cahora Bassa (
2600 km
2
; 50
km
3
)
Kariba Res.
Cahora Bassa Res.
Victoria Falls Zambezi Delta
Zambezi source Barotse Floodplains 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)
J u l A u g S e p O c t N o v D e c J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c J a n F e b M a r A p r M a y J u n J u l 0 50 100 150 200 250 Dry Season May-Sep (40 mm) M o n th ly P re c ip it a ti o n [ m m ] 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 m
3
s
-1
1 0 /1 /2 0 1 0 1 1 /1 /2 0 1 0 1 2 /1 /2 0 1 0 1 /1 /2 0 1 1 2 /1 /2 0 1 1 3 /1 /2 0 1 1 4 /1 /2 0 1 1 5 /1 /2 0 1 1 6 /1 /2 0 1 1 7 /1 /2 0 1 1 8 /1 /2 0 1 1 9 /1 /2 0 1 1 1 0 /1 /2 0 1 1 1 1 /1 /2 0 1 1 1 2 /1 /2 0 1 1 1 /1 /2 0 1 2 2 /1 /2 0 1 2 3 /1 /2 0 1 2 4 /1 /2 0 1 2 5 /1 /2 0 1 2 6 /1 /2 0 1 2 7 /1 /2 0 1 2 8 /1 /2 0 1 2 9 /1 /2 0 1 2 1 0 /1 /2 0 1 2 1 1 /1 /2 0 1 2 1 2 /1 /2 0 1 2 1 /1 /2 0 1 3 2 /1 /2 0 1 3 3 /1 /2 0 1 3 4 /1 /2 0 1 3 5 /1 /2 0 1 3 6 /1 /2 0 1 3 7 /1 /2 0 1 3 8 /1 /2 0 1 3 9 /1 /2 0 1 3 1 0 /1 /2 0 1 3 1 1 /1 /2 0 1 3 1 2 /1 /2 0 1 3 1 /1 /2 0 1 4
0
1000
2000
3000
4000
5000
6000
7000
8000
2010-2011 Wet SeasonD
is
c
h
a
rg
e
[
m
3s
-1]
Date [mm/dd/yy]
Victoria Falls Kariba Dam Dry Season 2011-2012 2012-2013Sampling 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
1 0 /1 /2 0 1 0 1 1 /1 /2 0 1 0 1 2 /1 /2 0 1 0 1 /1 /2 0 1 1 2 /1 /2 0 1 1 3 /1 /2 0 1 1 4 /1 /2 0 1 1 5 /1 /2 0 1 1 6 /1 /2 0 1 1 7 /1 /2 0 1 1 8 /1 /2 0 1 1 9 /1 /2 0 1 1 1 0 /1 /2 0 1 1 1 1 /1 /2 0 1 1 1 2 /1 /2 0 1 1 1 /1 /2 0 1 2 2 /1 /2 0 1 2 3 /1 /2 0 1 2 4 /1 /2 0 1 2 5 /1 /2 0 1 2 6 /1 /2 0 1 2 7 /1 /2 0 1 2 8 /1 /2 0 1 2 9 /1 /2 0 1 2 1 0 /1 /2 0 1 2 1 1 /1 /2 0 1 2 1 2 /1 /2 0 1 2 1 /1 /2 0 1 3 2 /1 /2 0 1 3 3 /1 /2 0 1 3 4 /1 /2 0 1 3 5 /1 /2 0 1 3 6 /1 /2 0 1 3 7 /1 /2 0 1 3 8 /1 /2 0 1 3 9 /1 /2 0 1 3 1 0 /1 /2 0 1 3 1 1 /1 /2 0 1 3 1 2 /1 /2 0 1 3 1 /1 /2 0 1 4 0 1000 2000 3000 4000 5000 6000 7000 8000 2010-2011 Wet Season D is c h a rg e [ m 3 s -1] Date [mm/dd/yy] Victoria Falls Kariba Dam Dry Season
biweekly monitoring: Zambezi and Kafue
Wet 2012 D ry 2 0 1 3 2011-2012 2012-2013 Wet 2013
Measured parameters
•
Physico-chemical: pH, O
2
, t°, conductivity, Total Alkalinity
•
Total Suspended Matter (
TSM) and sediment characterization
•
Concentration and stable isotope (δ
13
C and δ
15
N) composition
of
POC, PN, DOC, DIC
•
Aquatic metabolism: community respiration, primary production
•
GHG (CO
2
, CH
4
, N
2
O) concentrations and fluxes
Headspace Technique
Membrane Equilibrator
Floating chamber
TSM – spatio-temporal dynamics
0 200 400 600 800 1000 1200 1400 1600 1 10 100 1000 Lukanga SwampsITT Res. (2012 wet) ITT Res. (2013 wet) ITT Res. (2013 dry)
T S M K a fu e R iv e r [m g 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) C.B. Res. (2013 wet) Kariba Res. (2012 wet)
Kariba Res. (2013 wet) Kariba Res. (2013 dry) ZBZ (2012 wet) ZBZ (2013 wet) ZBZ (2013 dry) T S M Z a m b e z i R iv e r [m g L -1 ]
Distance from source [km]
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 T S M [ m g L -1 ] p>0.109 p>0.912 NO interannual variability NO distinct seasonalityTSM – spatio-temporal dynamics
0 200 400 600 800 1000 1200 1400 1600 1 10 100 1000 Lukanga SwampsITT Res. (2012 wet) ITT Res. (2013 wet) ITT Res. (2013 dry)
T S M K a fu e R iv e r [m g 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) C.B. Res. (2013 wet) Kariba Res. (2012 wet)
Kariba Res. (2013 wet) Kariba Res. (2013 dry) ZBZ (2012 wet) ZBZ (2013 wet) ZBZ (2013 dry) T S M Z a m b e z i R iv e r [m g L -1 ]
Distance from source [km]
Shire River (6-11 mg L-1)
Zambezi River
Kafue River
Zam bezi Karib a R es. C.B. Res . Kabo mpo Kafue ITT Res . Lung a Luan gwa Luns emfw a Maz oe Shire 1 10 100 1000 T S M r a n g e [ 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 T S M [ m g L -1 ] p>0.109 p>0.912 NO interannual variability NO distinct seasonalityPOC, PN, δ
13
C
POC
, C:N ratio
1 10 100 1000 0.1 1 10 100 % P N [ % ] TSM [mg L-1] 1 10 100 1000 0.1 1 10 100 ITT Res. Lunga Luangwa Lunsemfwa Mazoe Shire Zambezi Kariba Res. C.B. Res. Kabompo Kafue % P O C [ % ] -33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 0.1 1 10 100 Lunga Luangwa Lunsemfwa Mazoe Shire Zambezi Kariba Res. C.B. Res Kabompo Kafue ITT Res. P e rc e n t P O C [ % ] δ13C POC [‰] -33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 2 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 M o la r C :N r a tio δ13C POC [‰]POC - predominantly terrestrial (C3) origin:
Luangwa
– more towards C4 soil C;
Reservoirs – fraction from phytoplankton
DOC– spatio-temporal dynamics
Zambezi River
Kafue River
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 Shire River C.B. Res. (2012 wet) C.B. Res. (2013 wet) Kariba Res. (2012 wet)
Kariba Res. (2013 wet) Kariba res. (2013 dry) ZBZ (2012 wet) ZBZ (2013 wet) ZBZ (2013 dry) D O C Z a m b e z i R iv e r [m g L -1 ]
Distance from source [km]
Barotse Floodplains 0 200 400 600 800 1000 1200 1400 1600 0.0 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)
D O C K a fu e R iv e r [m g L -1 ]
Distance from source [km]
Kafue (2012 wet) Kafue (2013 wet) Kafue (2013 dry) Zam bezi Karib a R es. C.B . Res . Kabo mpo Kafue I.T.T . Res . Lung a Luan gwa Luns emfw a Maz oe Shire 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 R a n g e D O C [ m g L -1 ]
Wet 2012 Wet 2013 Dry 2013 G1 Wet 2012 Wet 2013 Dry 2013
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 D O C [ m g L -1 ]
Zambezi
Kafue
p>0.002 p>0.018 p>0.258 p>0.019 Distinct seasonalityDOC isotopic signature (δ
13
C
DOC
), and Age (∆
14
C
POC
, ∆
14
C
DOC
)
-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. δ 1 3 C D O C [ ‰ ] δ13C POC [‰] 1:1 0 1000 2000 3000 -20 -10 0 10 20 30 40 50 60 70 80
Distance from source [km]
∆ 1 4 C P O C [ ‰ ] 20 30 40 50 60 70 80 90 100 110 120 Zambezi (∆14C DOC) Reservoirs (∆14CDOC) Tributaries (∆14CDOC) Zambezi (∆14C POC) Reservoirs (∆14CPOC) Tributaries (∆14CPOC) ∆ 1 4 C D O 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
Distance from source [km]
δ 1 3 C D O C [ ‰ ] Zambezi Reservoirs δ 1 3 C D O C [ ‰ ] DOC [mg L-1] r2 = 0.5
DOC – mostly C3 origin with minimal
in-stream autochthonous production
δ
13
C
DOC
: δ
13
POC
– decupling
between DOC and POC sources
∆
14
C – modern nature of riverine
Carbon Mass
Balance
Area Q TSM POC DOC DIC CO2 CH4 C Yield GHG C Deposition C Export
[km2] [m3s-1] [kt C yr-1]
Zambezi at Delta 11445 3779
9558
306
263
3672
2681 46.1 7163 2727 196 4240Kafue at M.S. 658 314
196
8
45
205
459 4.6 738464
16
258
Zambezi at M.S. 6403 1237