Temporal variability and spatial dynamics of CO2 and CH4 concentrations and fluxes in the Zambezi River system

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Temporal variability and spatial dynamics of

CO

₂

and CH

₄

concentrations and fluxes

in the Zambezi River system

AFRIVAL Project (African River Basins) http://ees.kuleuven.be/project/afrival/ EGU General Assembly 2014, Vienna

Cristian R. Teodoru

1

_{, Alberto V. Borges}

2

_{, Steven Bouillon}

1

_{, Frank C. Nyoni}

3

_and

Imasiku Nyambe

3

1_{K.U. Leuven, Belgium;}2_{University of Liege, Belgium;}3_{University of Zambia, IWRM Center, Zambia}

EGU General Assembly Vienna, 2014

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Introduction:

Zambezi River Basin

The Zambezi River Basin – general characteristics

• 4th_{larges in Africa and the largest (from Africa) flowing in to the Indian Ocean}

• Total length: over 3000 km; Drainage basin: ~ 1.4 Mio km2_{(shared by 8 countries)}

• Main tributaries: Lungwebungu (115 m3_/s), Kabompo _{(270 m}3_/s), Luangina _{(65 m}3_/s), Kwando

(53 m3_/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 (5580 km2_{; 180 km}3_{), and Cahora Bassa (2670 km}2_{; 52 km}3₎

Kariba Res.

Cahora Bassa Res.

Victoria Falls Zambezi Delta

Zambezi source

Barotse Floodplains

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Introduction:

Zambezi River Basin

The Zambezi River Basin – climate and rainfall

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

• 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) • 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 (900 mm) 2. Dry season (May – Sep/Oct), corresponding to winter, with 5% of annual rainfall (40 mm). Dry

season is further divided into cold dry: May-Aug and hot dry: Aug-Sep/Oct.

Jul _Aug S ep _Oct N ov D ec _Jan Fe b M ar A pr M ay _Jun _Jul A ug S ep _Oct N ov D ec _Jan Fe b M ar A pr M ay _Jun _Jul 0 50 100 150 200 250 Dry Season May-Sep (40 mm) M ont hly Prec ipit at ion [m m ] Wet Season Oct-Apr (900 mm)

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Introduction:

Zambezi River Basin

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: 3800-4130 m3_s-1

9-15-201 0 10 -15 -20 10 11 -15 -20 10 12 -15 -20 10 1-15-201 1 2-15-201 1 3-15-201 1 4-15-201 1 5-15-201 1 6-15-201 1 7-15-201 1 8-15-201 1 9-15-201 1 10 -15 -20 11 11 -15 -20 11 12 -15 -20 11 1-15-201 2 2-15-201 2 3-15-201 2 4-15-201 2 5-15-201 2 6-15-201 2 7-15-201 2 8-15-201 2 9-15-201 2 10 -15 -20 12 11 -15 -20 12 12 -15 -20 12 1-15-201 3 2-15-201 3 3-15-201 3 4-15-201 3 5-15-201 3 6-15-201 3 7-15-201 3 8-15-201 3 9-15-201 3 10 -15 -20 13 11 -15 -20 13 0 1000 2000 3000 4000 5000 6000 7000 8000 Wet Season 2012-2013 2011-2012 D is charge [ m 3 s -1 ] Victoria Falls Kariba Dam 2010-2011 Dry Season Date [mm/dd/yy]

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Sampling & Methods

Sampling Strategy

• 3 sampling campaigns: Wet (Feb-Apr) 2012, Wet (Jan-Apr) 2013, Dry (Oct-Dec) 2013 • Over 50 sampling sites: 26 along Zambezi (Kariba & CB), 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

9-15-201 0 10 -15 -20 10 11 -15 -20 10 12 -15 -20 10 1-15-201 1 2-15-201 1 3-15-201 1 4-15-201 1 5-15-201 1 6-15-201 1 7-15-201 1 8-15-201 1 9-15-201 1 10 -15 -20 11 11 -15 -20 11 12 -15 -20 11 1-15-201 2 2-15-201 2 3-15-201 2 4-15-201 2 5-15-201 2 6-15-201 2 7-15-201 2 8-15-201 2 9-15-201 2 10 -15 -20 12 11 -15 -20 12 12 -15 -20 12 1-15-201 3 2-15-201 3 3-15-201 3 4-15-201 3 5-15-201 3 6-15-201 3 7-15-201 3 8-15-201 3 9-15-201 3 10 -15 -20 13 11 -15 -20 13 0 1000 2000 3000 4000 5000 6000 7000 8000

biweekly monitoring: Zambezi and Kafue

D ry 2 0 1 3 Wet 2012 Wet Season 2012-2013 2011-2012 D is charge [ m 3 s -1 ] Victoria Falls Kariba Dam 2010-2011 Dry Season Wet 2013 Date [mm/dd/yy]

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Sampling and Methods:

Parameters

Measured parameters

• Physico-chemical: pH, O₂, T, conductivity, TA, nutrients, major elements

• Total Suspended Matter (TSM)

• Concentration and stable isotope (δ13_{C and δ}15_{N) composition of POC,}

DOC, DIC, PN and POP

• Aquatic metabolism: community respiration & primary production • GHG (CO₂, CH₄, N₂O) concentrations and fluxes

Headspace Technique Membrane Equilibrator In-situ pCO₂ measurements

0 2000 4000 6000 8000 10000 12000 14000 16000 0 2000 4000 6000 8000 10000 12000 14000 16000 pCO 2 M em brane equilibrat or [ppm ] pCO₂ Headspace [ppm] r2 = 0.99, n = 82

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Drift mode

Static mode

Sampling and Methods:

Parameters

0 1000 2000 3000 4000 5000 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0 1000 2000 3000 4000 5000 FC O2 S ta tic - FC O 2 D ri ft Water Velocity [m s-1] M ea su re d C O 2 F L u x [m m o l C m -2 d -1 ] Sampling site drift static

Flux measurements: Floating chamber

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FCO₂ Total FCH₄

Floating chamber

F_CO2 = k ΔCO₂ k = F_CO2 / ΔCO₂

Diffusive F_CH4 = k ΔCH₄ Total F_CH4 = diffusive F_CH4 + Ebullitive F_CH4

0 2 4 6 8 10 12 400 600 800 1000 1200 1400 pCO 2 [p pm ] Time [min]

Increase in gas conc. over time

0 5 10 15 20 25 30 35 400 600 800 1000 1200 1400 pCO 2 [p pm ] Time [min] low pCO₂ high pCO₂

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Results:

CO

₂

– spatio-temporal dynamics

0 500 1000 1500 2000 2500 3000 0 2000 4000 6000 8000 10000 12000 14000 _{C.B. Res. (2012 wet)} C.B. Res. (2013 wet) Kariba Res. (2012 wet)

Kariba Res. (2013 wet) Kariba Res. (2013 dry)

pCO

2

[

ppm]

Distance from source [km]

Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) Barotse Floodplains Caprivi-Chobe Floodplains

Kariba & CB Dam hypolimnetic water release

Shire >13000 ppm

Degassing Vic. Falls

0 200 400 600 800 1000 1200 1400 1600 0 2000 4000 6000 8000 10000 12000 14000 atm. CO₂ pCO 2 [ ppm]

Kafue (2012 wet) Kafue (2013 wet) Kafue (2013 dry) ITT Res. (2012 wet) ITT Res. (2013 wet) ITT Res. (2013 dry)

Kafue Flats

Kafue Gorge Reservoir

Wet Dry J1 Wet Dry

0 2000 4000 6000 8000 10000 12000 14000 p CO 2 [p pm] Zambezi 2013 Kafue 2013 p>0.085 p>0.017 Zam bezi Karib a Re s. C. B . Res.

Kabompo Kaf

ue ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire -1000 0 1000 2000 3000 4000 5000 6000 7000 12000 14000 Ran ge p CO 2 [p pm] (Aufdenkempe et al., 2011) Tropical streams (4300) Tropical lakes/reservoirs (1900) Tropical rivers (3600)

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Results:

CO

₂

– spatio-temporal dynamics

0 500 1000 1500 2000 2500 3000 0 2000 4000 6000 8000 10000 12000 14000 _{C.B. Res. (2012 wet)} C.B. Res. (2013 wet) Kariba Res. (2012 wet)

Kariba Res. (2013 wet) Kariba Res. (2013 dry)

pCO

2

[

ppm]

Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) Barotse Floodplains Caprivi-Chobe Floodplains

Kariba & CB Dam hypolimnetic water release

Shire >13000 ppm

Degassing Vic. Falls

0 200 400 600 800 1000 1200 1400 1600 0 2000 4000 6000 8000 10000 12000 14000 atm. CO₂ pCO 2 [ ppm]

Kafue Flats

Kafue Gorge Reservoir

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Results:

CH

₄

– spatio-temporal dynamics

0 500 1000 1500 2000 2500 3000 0 1000 2000 3000 4000 12000 14000

Kafue Res. (2012 wet) Kafue Res. (2013 wet) Kafue Res. (2013 dry) C.B. Res. (2012 wet) C.B. Res. (2013 dry) Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) CH 4 [ nmol L -1 ]

Distance from source [km] 0 200 400 600 800 1000 1200 1400 1600

0 200 400 600 800 1000 1200 CH 4 [ nmol L -1 ]

DIstance from source [km]

Kafue (2012 wet) Kafue (2013 wet) Kafue (2013 dry) ITT Res. (2012 wet) ITT Res. (2013 wet) ITT REs. (2013 dry)

0 2000 4000 6000 8000 10000 12000 14000 0 500 1000 1500 2000 2500 3000 3500 4000 Lunga Luangwa Lunsemfwa Mazoe Shire Zambezi Kariba Res. C.B. Res Kabompo Kafue ITT Res. CH 4 [ nm ol L -1 ] pCO₂ [ppm]

Wet Dry E2 Wet Dry

0 200 400 600 800 1000 CH 4 [n m ol L -1 ] Zambezi 2013 Kafue 2013 p>0.24 p>0.49

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Results:

N

₂

O – spatio-temporal dynamics

Zam bezi Karib a Re s. C.B. Res.

Kabompo Kaf

ue ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire 0.0 2.0 4.0 6.0 8.0 10.0 12.0 Ran ge N 2 O [n m ol L -1 ] 0 2000 4000 6000 8000 10000 12000 14000 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Lunga Luangwa Lunsemfwa Mazoe Shire Zambezi Kariba Res. C.B. Res. Kabompo Kafue ITT Res. N 2 O [ nmol L -1 ] pCO₂ [ppm]

Wet Dry C Wet Dry

2 4 6 8 10 12 N 2 O [n m ol L -1 ] Zambezi 2013 Kafue 2013 p>0.0005 p>0.0006

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Results:

DIC - spatio-temporal variability

0 200 400 600 800 1000 1200 1400 1600 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Kafue (2012 wet) Kafue (2013 wet) Kafue (2013 dry) ITT Res. (2012 wet) ITT Res. (2013 wet) ITT Res. (2013 dry)

D IC [ m m ol L -1 ]

0 500 1000 1500 2000 2500 3000 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

4.0 _{Kariba Res. (2012 wet)} Kariba Res. (2013 wet) Kariba Res. (2013 dry)

C.B. Res. (2012 wet) C.B. Res. (2013 wet) Shire DIC > 2 Barotse Floodplains Kabompo DIC >1.6 Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) D IC [ m m ol L -1 ]

Zam bezi Karib a Re s. C.B. Res.

Kabompo Karib

a ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Ran ge DIC [mm ol L -1 ]

Wet Dry C Wet Dry

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 DIC [m m ol L -1 ] Zambezi 2013 Kafue 2013 p>0.25 p>0.013

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Results:

δ

13

_C

DIC

- spatio-temporal variability

0 500 1000 1500 2000 2500 3000 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) Kariba Res. (2012 wet) Kariba Res. (2013 wet) Kariba Res. (2013 dry) C.B. Res. (2012 wet) C.B. Res. (2013 wet)  13 C D IC [ ‰]

0 200 400 600 800 1000 1200 1400 1600 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 Kafue (2012 wet) Kafue (2013 wet) Kafue (2013 dry) ITT Res. (2012 wet) ITT Res. (2013 wet) ITT Res. (2013 dry)

 13 C D IC [ ‰]

Zam bezi Karib a Re s. C.B. Res. Kab ompo Kafue ITT Res. Lung a Luan gwa Lnsemf wa Maz oe Shire -24 -22 -12 -10 -8 -6 -4 -2 0  13 C D IC [‰]

Wet Dry I Wet Dry

-25 -20 -15 -10 -5 0  13 C D IC [‰] Zambezi 2013 Kafue 2013 p>0.8 p>0.03

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Results:

DIC & δ

13

_C

DIC

• Zambezi and Kafue rivers have δ13_C

DIC -7

• δ13_C

DIC enrichment => carbonate weathering /dissolution

and/or downstream degassing of groundwater • Reservoirs δ13_C

DIC - outgassing & photosyntesis

• Kabompo, Lunga, Luangwa, Lunsemfwa => increased contribution of soil CO₂ with C4 vegetation (~ -9‰) or weathering 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 Lunga Luangwa Lunsemfwa Mazoe Shire Zambezi Kariba Res. C.B. Res. Kabompo Kafue ITT Res.  13 C D IC [ ‰] DIC [mmol L-1] 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0  13 C D IC [ ‰] pH [NBS] Zambezi Kariba Res. C.B. Res. Kabompo Kafue ITT Res. Lunga Luangwa Lunsemfwa Mazoe Shire

River DIC [mmol L-1_{] δ}13_C

DIC [‰] Zambezi 1.11 -7.72 Kafue 1.83 -7.33 Kariba Res. 0.76 -2.93 C.B. Res. 1.09 -2.90 ITT Res. 1.49 -5.19 Kabompo 0.81 -10.74 Lunga 1.84 -9.78 Luangwa 1.05 -9.43 Lunsemfwa 0.86 -8.92 Mazoe 1.04 -4.21 Shire 2.32 -5.09

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Results:

Fluxes to atmosphere - CO

₂

and CH

₄ 0 2000 4000 6000 8000 10000 12000 14000 0 5000 10000 15000 20000 25000 30000 35000 _Zambezi Kariba Res. C.B. Res Kafue ITT Res. Lunga Luangwa Lunsemfwa Mazoe Shire CO 2 f lux [ m g c m -2 d -1 ] pCO₂ [ppm] 0 500 1000 1500 2000 0 50 100 150 200 Zambezi Kariba Res. C.B. Res Kafue ITT Res. Lunga Luangwa Lunsemfwa Mazoe CH 4 f lux [ m g C m -2 d -1 ] CH₄ [nmol L-1]

Wet Dry B Wet Dry

0 20 40 60 80 100 CH 4 fl ux [mg C m -2 d -1 ] Zambezi 2013 Kafue 2013 p>0.14 p>0.41

Wet Dry K1 Wet Dry

0 2500 5000 7500 10000 12500 20000 25000 CO 2 flux [mg C m -2 d -1 ] Zambezi 2013 Kafue 2013 p>0.39 p>0.13

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Results:

Mass Balance

Area CO₂ flux CH₄ flux CO₂ CH₄

[km2_] _{[mg C m}-2 _d-1_] _{[kt C yr-}1_] Zambezi 1879 4291 45.0 3870 40.7 Kariba Res. 5580 -191 4.8 -389 9.7 C.B. Res. 2670 -356 1.4 -347 1.4 Kafue 287 2962 20.0 310 2.1 ITT Res. 364 1102 18.1 146 2.4 KG 7.4 956 17.4 3 0.05 Total 10787 677 27 3594 56 Carbon Budget Zambezi River

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Conclusions

 pH, SpC, TA, DIC and d13CDIC - display a longitudinal pattern (increase towards the ocean) with overall low interannual variability

Seasonality (higher DIC conc. and more enriched d13CDIC) more pronounced in the headwaters (upstream of reservoirs)

All rivers are oversaturated in CO2, CH4 in respect to atmospheric concentrations CO2 and CH4 spatial dynamics – driven by the presence/absence of

floodplains/wetlands; Lower conc. during dry seasons – due to loss of connectivity with wetlands

Reservoirs are sinks of CO2 and source of CH4

N2O – high seasonality (higher conc. during dry season)

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Thank you for your attention!

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0 4000 8000 12000 16000 20000 0 4000 8000 12000 16000 20000 pCO 2 cal cul ated [ ppm] pCO₂ measured [ppm] 0 2000 4000 6000 8000 10000 12000 14000 0 500 1000 1500 2000 2500 3000 3500 4000 Lunga Luangwa Lunsemfwa Mazoe Shire Zambezi Kariba Res. C.B. Res Kabompo Kafue ITT Res. CH 4 [ nm ol L -1 ] pCO₂ [ppm] Zam bezi Karib a Re s. C.B. Res.

Kabompo Kaf

ue ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire 0 500 1000 12000 Ran ge CH 4 [n m ol L -1 ] Zam bezi Karib a Re s. C. B . Res.

Kabompo Kaf

ue ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire 0 2000 4000 6000 12000 14000 Ran ge p CO 2 [p pm]

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Results:

CO

₂

dynamics

-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 2000 4000 6000 8000 10000 12000 14000 R2_=0.7 Zambezi K CB Kafue ITT Luangwa pCO 2 [p pm ] 13_{C-DIC [‰]} R2 =0.6

Zambezi Kafue Luangwa K CB ITT 0 1000 2000 3000 4000 5000 6000 12000 14000 Tropical lakes/reservoirs (1900) pCO 2 [p pm ] _{Tropical streams (4300)} Tropical rivers (3600) (Aufdenkempe et al., 2011) 0 20 40 60 80 100 120 140 160 0 2000 4000 6000 8000 10000 12000 14000 Zambezi Kafue Luangwa K CB ITT pCO 2 [p pm ] Dissolved Oxygen [%]

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Results:

Landscape Characteristics

0.0 200.0k 400.0k 600.0k 800.0k 1.0M 1.2M 1.4M 0 200 400 600 800 1000 1200 1400 1600 _Zambezi Kariba Res. C.B. Res. Kabompo Kafue ITT Res. Lunga Luangwa Lunsemfwa E levati on [ m ] Catchment [km2] r2_{= 0.95} 0.0 200.0k 400.0k 600.0k 800.0k 1.0M 1.2M 1.4M 0 500 1000 1500 2000 2500 3000 r2_{= 0.97} Zambezi Kariba Res. C.B. Res. Kabompo Kafue ITT Res. Lunga Luangwa Lunsemfwa D ist ance f rom source [ km ] Catchment [km2] r2 = 0.97 0 500 1000 1500 2000 2500 3000 0 200 400 600 800 1000 1200 1400 1600 Zambezi Kariba Res. C.B. Res. Kabompo Kafue I.T.T. Res. Lunga Luangwa Lunsemfwa E levati on [ m ]

r2_{= 0.96}

r2_{= 0.5}

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Results:

pH

pH - Spatial variability along the Zambezi River during wet season 2012

0 500 1000 1500 2000 2500 3000 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Kafue pH > 8.2 C.B. Res. (2012 wet) Kariba Res. (2012 wet)

Kariba Dam hypolimnetic water release Barotse Floodplains Caprivi-Chobe Floodplains Shire pH ~ 7.0 Victoria Falls CO₂ degassing pH [ N B S ]

Zambezi (2012 wet)

Kabompo pH > 7.5

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Results:

pH - spatio-temporal variability

0 500 1000 1500 2000 2500 3000 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 C.B. Res. (2012 wet) C.B. Res. (2013 dry) Kariba Res. (2012 wet)

Kariba Res. (2013 wet) kariba Res. (2013 dry)

pH [ N B S ]

Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) 0 200 400 600 800 1000 1200 1400 1600 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Kafue Gorge Reservoir Lunga pH > 7.8

ITT Res. (2012 wet) ITT Res. (2013 wet) ITT Res. (2013 dry)

Lukanga Swamps Kafue Flats pH [ N B S ]

Kafue (2012 wet) Kafue (2013 wet) Kafue (2013 dry) Zam bezi Karib a Re s. C.B. Res. Kab ompo Kafue ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Ran ge p H [NBS]

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Results:

Conductivity & Total Alkalinity

0 200 400 600 800 1000 1200 1400 1600 0 100 200 300 400 500 600 700 Kafue Flats Lukanga Swamps S peci fic C ond uctance [ µ S cm -1 ]

Zam bezi Karib a Re s. C.B. Res. Kab ompo Kafue ITT Res. Lung a Luan gwa Lunse mfw a Maz oe Shire 0 100 200 300 600 Ran ge Sp C [µS c m -1 ] 0 100 200 300 400 500 600 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Zambezi Kariba Res. C.B. Res. Kabompo Kafue ITT Res Lunga Luangwa Lunsemfwa Mazoe Shire To tal A lkal ini ty [m m ol kg -1 ] Specific Conductance [µS cm-1] 0 500 1000 1500 2000 2500 3000 0 50 100 150 200 250 Kafue SpC > 220 Shire SpC > 230 SpC > 175 Barotse Floodplains Kabompo SpC > 165 Zambezi (2012 wet) Zambezi (2013 wet) Zambezi (2013 dry) S peci fic C ond uctance [ µ S cm -1 ]

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Introduction:

Zambezi River Basin

The Zambezi River Basin – Land Use & Land Cover

• 75% of area – forest and bush; 13% - cropland (rain-fed agriculture); and 8 % grassland

• 4 major biomes (Chenje, 2000)

• Zambezian (95% of basin): woodlands, grasslands, swamps and lakes

• Congolian : moist and warmer climate with tropical forest and miombo woodlands

• Montane (1800-2000 m a.s.l.): cooler, wetter: evergreen forest and grasslands

• Costal: no marked dry season, little temperature fluctuations, mostly dry forest and grasslands

Population in the basin

•31.7 millions in 1998, (1/3 of total population of the 8 basin countries), out of which over 85% leaves in Malawi, Zambia and Zimbabwe

•Ten years later (2008) the population reached over 40

million, and it is predicted to

achieve 51.2 million by 2025 (SADC/SARDC et al., 2012)