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River-wetland interaction and carbon cycling in a semi-arid riverine system: the Okavango Delta, Botswana

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Abstract

The Okavango River, in semi-arid northwestern Botswana, flows for over 400 km in a pristine wetland developed on a large (>22,000 km2) alluvial fan (Okavango Delta). An annual flood pulse inundates the floodplains of the wetlands and travels across the Delta in 4–6 months. In this study, we assess the effects of long hydraulic residence time, variable hydrologic interaction between river–floodplain–wetland and evapotranspiration on carbon cycling. We measured dissolved inorganic carbon (DIC) concentrations and stable carbon isotopes of DIC (δ13CDIC) from river water when the Delta was not flooded (low water) and during flooding (high water). During low water, the average DIC concentration was 31 % higher and the δ13CDIC 2.1 ‰ more enriched compared to high water. In the lower Delta with seasonally flooded wetlands, the average DIC concentration increased by 70 % during low water and by 331 % during high water compared to the Panhandle with permanently flooded wetlands. The increasing DIC concentration downriver is mostly due to evapoconcentration from transpiration and evaporation with increased transit time. The average δ13CDIC between low and high water decreased by 3.7 ‰ in the permanently flooded reaches compared to an increase of 1.6 ‰ in the seasonally flooded reaches. The lower δ13CDIC during high water in the permanently flooded reaches suggest that DIC influx from the floodplain-wetland affects river’s DIC cycling. In contrast, higher river channel elevations relative to the wetlands along seasonal flooded reaches limit hydrologic interaction and DIC cycling occurs mostly by water column processes and river-atmospheric exchange. We conclude that river-wetlands interaction and evapoconcentration are important factors controlling carbon cycling in the Okavango Delta.

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References

  • Atekwana EA, Krishnamurthy RV (1998) Seasonal variations of dissolved inorganic carbon and δ13C of surface waters: application of a modified gas evolution technique. J Hydrol 205:265–278

    Article  Google Scholar 

  • Aucour AM, Sheppard SMF, Guyomar O, Wattelet J (1999) Use of 13C to trace origin and cycling of inorganic carbon in the Rhône river system. Chem Geol 159(1–4):87–105

    Article  Google Scholar 

  • Baron J, McKnight D, Denning AS (1991) Sources of dissolved and particulate organic material in Loch Vale watershed, Rocky Mountain National Park, Colorado. USA. Biogeochemistry 15(2):89–110

    Google Scholar 

  • Bauer-Gottwein P, Langer T, Prommer H, Wolski P, Kinzelbach W (2007) Okavango Delta islands: interactions between density-driven flow and geochemical reactions under evapo-concentration. J Hydrol 335:389–405

    Article  Google Scholar 

  • Benson NM (2000) Geology and mineralization in the Meso- to Neoproterozoic Ghanzi-Chobe belt of northwest Botswana. J Afr Earth Sc 30(3):467–474

    Article  Google Scholar 

  • Boutton PW, Wong WW, Hachey DL, Lee LS, Cabrera MP, Klein PD (1983) Comparison of quartz and Pyrex tubes for combustion of organic samples for stable carbon isotope analysis. Anal Chem 55:1832–1833

    Article  Google Scholar 

  • Boyer EW, Hornberger GM, Bencala KE, McKnight DM (1997) Response characteristics of DOC flushing in an alpine catchment. Hydrol Process 11:1635–1647

    Article  Google Scholar 

  • Brunet F, Gaiero D, Probst JL, Depetris PJ, Gauthier Lafaye F, Stille P (2005) δ13C tracing of dissolved inorganic carbon sources in Patagonian rivers (Argentina). Hydrol Process 19(17):3321–3344

    Article  Google Scholar 

  • Brunet F, Dubois K, Veizer J, Nkoue Ndondo GR, Ndam Ngoupayou JR, Boeglin JL, Probst JL (2009) Terrestrial and fluvial carbon fluxes in a tropical watershed: Nyong basin Cameroon. Chemical Geology 265(3–4):563–572

    Article  Google Scholar 

  • Cartwright I (2010) The origins and behaviour of carbon in a major semi-arid river, the Murray River, Australia, as constrained by carbon isotopes and hydrochemistry. Appl Geochem 25(11):1734–1745

    Article  Google Scholar 

  • Cawley KM, Wolski P, Mladenov N, Rudolf Jaffé R (2012) Dissolved organic matter biogeochemistry along a transect of the Okavango Delta, Botswana. Wetlands. doi:10.1007/s13157-012-0281-0

    Google Scholar 

  • Cole JJ, Prairie YT, Caraco NF, McDowell WH, Tranvik LJ, Striegl RG, Duarte CM, Kortelainen P, Downing JA, Middelburg JJ, Melack J (2007) Plumbing the global carbon cycle: integrating inland waters into the terrestrial carbon budget. Ecosystems 10:171–184

    Article  Google Scholar 

  • Company Hach (1992) Water analysis handbook. Hach Company, Loveland

    Google Scholar 

  • Cronberg G, Gieske A, Martins E, Prince Nengu J, Stenstrom I-M (1996) Major ion chemistry, plankton, and bacterial assemblages of the Jao/Boro River, Okavango Delta, Botswana: the swamps and flood plains. Arch Fur Hydrobiol 107(Suppl):335–407

    Google Scholar 

  • Dalzell BJ, Filley TR, Harbor JM (2007) The role of hydrology in annual organic carbon loads and terrestrial organic matter export from a mid-western agricultural watershed. Geochim Cosmochim Acta 71(6):1448–1462

    Article  Google Scholar 

  • Dincer T, Hutton LG, Kupee BBJ (1979) Study, using stable isotopes, of flow distribution, surface-groundwater relations and evapotranspiration in the Okavango Swamp, Botswana. Isotope Hydrology 1978, vol. 1. International Atomic Energy Agency, Vienna, pp 3–25

    Google Scholar 

  • Doctor DH, Kendall C, Sebestyen SD, Shanley JB, Ohte N, Boyer EW (2008) Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream. Hydrol Process 22:2410–2423

    Article  Google Scholar 

  • Ellery K, Ellery WN, Verhagen BTh (1992) The distribution of C3 plant and C4 plants in a successional sequence in the Okavango Delta. S Afr J Bot 58:400–402

    Google Scholar 

  • Ellery W, McCarthy T, Smith N (2003) Vegetation, hydrology, and sedimentation patterns on the major distributary system of the Okavango fan, Botswana. Wetlands 23:357–375

    Article  Google Scholar 

  • Finlay JC (2003) Controls of stream water dissolved inorganic carbon dynamics in a forested watershed. Biogeochemistry 62(3):231–252

    Article  Google Scholar 

  • Gehre M, Geilmann H, Richter J, Werner RA, Brand WA (2004) Continuous flow 2H/1H and 18O/16O analysis of water samples with dual inlet precision. Rapid Commun Mass Spectrom 18:2650–2660

    Article  Google Scholar 

  • Gieske A (1997) Modeling outflow from the Jao/Boro River system in the Okavango Delta, Botswana. J Hydrol 193:214–239

    Article  Google Scholar 

  • Graneli W, Lindell M, Tranvik L (1996) Photo-oxidative production of dissolved inorganic carbon in lakes of different humic content. Limnol Oceanogr 41:698–706

    Article  Google Scholar 

  • Gumbricht T, McCarthy J, McCarthy TS (2004) Channels, wetlands and islands in the Okavango Delta, Botswana, and their relation to hydrological and sedimentological processes. Earth Surf Proc Land 29:15–29

    Article  Google Scholar 

  • Hem JD (1985) Study and interpretation of the chemical characteristics of natural water. US Geological Survey Water-Supply Paper 2254. Washington, DC

  • Hornberger GM, Bencala KE, McKnight DM (1994) Hydrological controls on dissolved organic carbon during snow melt in the Snake River near Montezuma, Colorado. Biogeochemistry 25(3):147–165

    Article  Google Scholar 

  • Huntsman-Mapila P, Mapila T, Letshwenyo M, Wolski P, Hemond C (2006) Characterization of arsenic occurrence in the water and sediments of the Okavango Delta, NW Botswana. Applied Geochemistry 21(8):1376–1391

    Article  Google Scholar 

  • Huntsman-Mapila P, Nsengimana H, Torto N, Diskin S (2011) Arsenic distribution and geochemistry in island groundwater of the Okavango Delta in Botswana. Sustain Groundw Resour 55–67:67. doi:10.1007/978-90-481-3426-7_4

    Google Scholar 

  • Kanduč T, Szramek K, Ogrinc N, Walter L (2007) Origin and cycling of riverine inorganic carbon in the Sava River watershed (Slovenia) inferred from major solutes and stable carbon isotopes. Biogeochemistry 86(2):137–154

    Article  Google Scholar 

  • Karberg NJ, Pregitzer KS, King JS, Friend AL, Wood JR (2005) Soil carbon dioxide partial pressure and dissolved inorganic carbonate chemistry under elevated carbon dioxide and ozone. Oecologia 142(2):296–306

    Article  Google Scholar 

  • Kinabo BD, Atekwana EA, Hogan JP, Modisi MP, Wheaton DD, Kampunzu AB (2007) Early structural development of the Okavango rift zone, NW Botswana. Afr Earth Sci 48:125–136

    Article  Google Scholar 

  • Kinabo BD, Hogan JP, Atekwana EA, Abdelsalam MG, Modisi MP (2008) Fault growth and propagation during incipient continental rifting: insights from a combined aeromagnetic and Shuttle Radar Topography Mission digital elevation model investigation of the Okavango Rift Zone, northwest Botswana. Tectonics 27:3013

    Article  Google Scholar 

  • Mackay A, Davidson T, Wolski P, Mazebedi R, Masamba W, Huntsman-Mapila P, Todd M (2011) Spatial and seasonal variability in surface water chemistry in the Okavango Delta, Botswana: a multivariate approach. Wetlands 31:815–829

    Article  Google Scholar 

  • Masamba WRL, Mazvimavi D (2008) Impact on water quality of land uses along Thamalakane-Boteti River: an outlet of the Okavango Delta. Phys Chem Earth Parts A/B/C 33(8–13):687–694

    Article  Google Scholar 

  • McCarthy TS, Ellery WN (1994) The effect of vegetation on soil and ground water chemistry and hydrology of islands in the seasonal swamps of the Okavango Fan, Botswana. J Hydrol 154:169–193

    Article  Google Scholar 

  • McCarthy TS, Ellery WN (1995) Sedimentation on the distal reaches of the Okavango Fan, Botswana, and its bearing on calcrete and silcrete (ganister) formation. J Sediment Res 65:77–90

    Article  Google Scholar 

  • McCarthy TS, Metcalfe J (1990) Chemical sedimentation in the semi-arid environment of the Okavango Delta, Botswana. Chem Geol 89(1–2):157–178

    Article  Google Scholar 

  • McCarthy TS, Ellery WN, Stanistreet IG (1992) Avulsion mechanisms on the Okavango fan, Botswana: the control of a fluvial system by vegetation. Sedimentology 39:779–795

    Article  Google Scholar 

  • McCarthy TS, Ellery WN, Ellery K (1993) Vegetation-induced, subsurface precipitation of carbonate as an aggradational process in the permanent swamps of the Okavango (delta) fan, Botswana. Chem Geol 107:111–131

    Article  Google Scholar 

  • McCarthy TS, Ellery WN, Bloem A (1998) Some observations on the geomorphological impact of hippopotamus (Hippopotamus amphibius L.) in the Okavango Delta, Botswana. Afr J Ecol 36:44–56

    Article  Google Scholar 

  • McCarthy TS, Cooper GRJ, Tyson PD, Ellery WN (2000) Seasonal flooding in the Okavango Delta, Botswana-recent history and future prospects. S Afr J Sci 96:25–33

    Google Scholar 

  • McCarthy JM, Gumbricht T, McCarthy T, Frost P, Wessels K, Seidel F (2003) Flooding patterns of the Okavango wetland in Botswana between 1972 and 2000. Ambio 32(7):453–457

    Google Scholar 

  • Meybeck M (1982) Carbon, nitrogen and phosphorus transport by World Rivers. Am J Sci 282:401–450

    Article  Google Scholar 

  • Milzow C, Kgotlhang L, Bauer-Gottwein P, Meier P, Kinzelbach W (2009) Regional review: the hydrology of the Okavango Delta, Botswana-processes, data and modeling. Hydrogeol J 17:1297–1328

    Article  Google Scholar 

  • Mladenov N, McKnight D, Wolski P, Ramberg L (2005) Effects of annual flooding on dissolved organic carbon dynamics within a pristine wetland, the Okavango Delta, Botswana. Wetlands 25:622–638

    Article  Google Scholar 

  • Mladenov N, McKnight DM, Macko SA, Ramberg L, Cory RM, Norris M (2007a) Chemical characterization of DOM in channels of a seasonal wetland. Aquat Sci 69:456–471

    Article  Google Scholar 

  • Mladenov N, McKnight DM, Wolski P, Murray-Hudson M (2007b) Simulation of DOM fluxes in a seasonal floodplain of the Okavango Delta, Botswana. Ecol Model 205:181–195

    Article  Google Scholar 

  • Mmualefe LC, Torto N (2011) Water quality in the Okavango Delta. Water SA 37(3):411–418

    Article  Google Scholar 

  • Modisi MP, Atekwana EA, Kampunzu AB, Ngwisanyi TH (2000) Rift kinematics during the incipient stages of continental extension: evidence from the nascent Okavango rift basin, northwest Botswana. Geology 28:939–942

    Article  Google Scholar 

  • Mook WG, Bommerson JC, Staverman WH (1974) Carbon isotope fractionation between dissolved bicarbonate and gaseous carbon dioxide. Earth Planet Sci Lett 22:169–176

    Article  Google Scholar 

  • Mosley-Bufford K, Atekwana EA, Abdelsalamc MG, Shemang E, Atekwana EA, Mickuse K, Moikwathai Moidaki M, Modisi MotsoptseP, Molwalefhe L (2012) Geometry and faults tectonic activity of the Okavango Rift Zone, Botswana: evidence from magnetotelluric and electrical resistivity tomography imaging. J Afr Earth Sc 65:61–71

    Article  Google Scholar 

  • Murphy KJ, Dickinson G, Thomaz SM, Bini LM, Dick K, Greaves K, Kennedy MP, Livingstone S, McFerran H, Milne JM, Oldroyd J, Wingfield RA (2003) Aquatic plant communities and predictors of diversity in a sub-tropical river floodplain: the upper Rio Paraná, Brazil. Aquat Bot 77(4):257–276

    Article  Google Scholar 

  • Nash DJ, Endfield GH (2002) A 19th century climate chronology for the Kalahari region of central southern Africa derived from missionary correspondence. Int J Climatol 22:821–841

    Article  Google Scholar 

  • Quay PD, Wilbur DO, Richey JE, Hedges JI, Devol AH (1992) Carbon cycling in the Amazon River: implications from the 13C compositions of particles and solutes. Limnol Oceanogr 37(4):857–871

    Article  Google Scholar 

  • Raymond PA, Bauer JE, Caraco NF, Cole JJ, Longworth B, Petsch ST (2004) Controls on the variability of organic matter and dissolved inorganic carbon ages in northeast US rivers. Mar Chem 92(1–4):353–366

    Article  Google Scholar 

  • Richey JE, Melack JM, Aufdenkampe AK, Ballester VM, Hess LL (2002) Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416:617–620

    Article  Google Scholar 

  • Ringrose S, Harris C, Huntsman-Mapila P, Vink BW, Diskins S, Vanderpost C, Matheson W (2009) Origins of strandline duricrusts around the Makgadikgadi Pans (Botswana Kalahari) as deduced from their chemical and isotope composition. Sediment Geol 219:262–279

    Article  Google Scholar 

  • Sawula G, Martins E (1991) Major ion chemistry of the lower Boro River, Okavango Delta, Botswana. Freshw Biol 26:481–493

    Article  Google Scholar 

  • Telmer K, Veizer J (1999) Carbon fluxes, pCO2 and substrate weathering in a large northern river basin, Canada: carbon isotope perspectives. Chem Geol 159:61–86

    Article  Google Scholar 

  • Walker CD, Richardson SB (1991) The use of stable isotopes of water in characterizing the source of water in vegetation. Chem Geol 94:145–158

    Article  Google Scholar 

  • Wilson BH, Dincer T (1976) An introduction to the hydrology and hydrography of the Okavango Delta. In: Symposium on the Okavango Delta, Botswana Society, Gaborone, 33–48

  • Wolski P, Savenije HHG, Murray-Hudson M, Gumbricht T (2006) Modelling of the flooding in the Okavango Delta, Botswana, using a hybrid reservoir-GIS model. J Hydrol 331:58–72

    Article  Google Scholar 

  • Zeng FW, Masiello C (2010) Sources of CO2 evasion from two subtropical rivers in North America. Biogeochemistry 100(1):211–225

    Article  Google Scholar 

  • Zeng FW, Masiello C, Hockaday W (2011) Controls on the origin and cycling of riverine dissolved inorganic carbon in the Brazos River, Texas. Biogeochemistry 104(1):275–291

    Article  Google Scholar 

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Acknowledgments

Partial funding for this project was provided by the US National Science Foundation (NSF grant # OISE-0927841) under the International Research Experience for Students (IRES) initiative. The University of Botswana provided logistical support for fieldwork. We thank the government of Botswana (Ministry of Education) for providing us with research permits. Field assistance was provided by C. Geyer, N. Paizis, O. Kgaodi and T. Koontse for. We thank the Department of Water Affairs in Mohembo, the owners of Drostky Cabins and Sepopa Swamp Stop for providing access to the river from their property. We also thank the Department of Water Affairs (Botswana) and the Okavango Research Institute Monitoring Unit for discharge data.

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Authors and Affiliations

  1. Boone Pickens School of Geology, 105 Noble Research Center, Oklahoma State University, Stillwater, OK, 74078, USA

    Eric Akoko, Eliot A. Atekwana & Anna M. Cruse

  2. Department of Geology, University of Botswana, Private Bag UB00704, Gaborone, Botswana

    Loago Molwalefhe

  3. Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana

    Wellington R. L. Masamba

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  1. Eric Akoko
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  2. Eliot A. Atekwana
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Correspondence to Eliot A. Atekwana.

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Akoko, E., Atekwana, E.A., Cruse, A.M. et al. River-wetland interaction and carbon cycling in a semi-arid riverine system: the Okavango Delta, Botswana. Biogeochemistry 114, 359–380 (2013). https://doi.org/10.1007/s10533-012-9817-x

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