Variability in chemistry of surface and soil waters of an evapotranspiration-dominated flood-pulsed wetland: solute processing in the Okavango Delta, Botswana

Authors

  • Keotshephile Mosimane Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana
  • Eric Struyf ECOBE, Antwerp University, Universiteitsplein 1, Antwerp, Belgium
  • Mangaliso J Gondwe Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana
  • Patrick Frings Department of Geology, Lund University, Sölvegaten 12, Lund, Sweden
  • Dimitri van Pelt ECOBE, Antwerp University, Universiteitsplein 1, Antwerp, Belgium
  • Piotr Wolski Climate System Analysis Group, University of Cape Town, South Africa
  • Jonas Schoelynck ECOBE, Antwerp University, Universiteitsplein 1, Antwerp, Belgium
  • Jörg Schaller 1. Institute of General Ecology and Environmental Protection, Technische Universität Dresden, D-01062, Dresden, Germany; 2. Environmental Geochemistry, Bayreuth Center for Ecology and Environmental Research (BayCEER), University Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
  • Daniel J Conley Department of Geology, Lund University, Sölvegaten 12, Lund, Sweden
  • Mike Murray-Hudson Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana

DOI:

https://doi.org/10.4314/wsa.v43i1.13

Keywords:

wetland vegetation, water chemistry, pore water, surface water, emergent macrophyte sp.

Abstract

Water chemistry is important for the maintenance of wetland structure and function. Interpreting ecological patterns in a wetland system therefore requires an in-depth understanding of the water chemistry of that system. We investigated the spatial distribution of chemical solutes both in soil pore water and surface water, along island-floodplain-channel hydrological gradients in seasonally and permanently inundated habitats between major regions in the Okavango Delta, Botswana. Our results show that major cations (Ca, Na, Mg, and K), dissolved silica (DSi), dissolved boron (B), dissolved organic matter (DOC) and electrical conductivity increased significantly, at p ≤ 0.05, from the inlet of the Delta (the Panhandle) to the distal downstream reaches, suggesting the influence of evapoconcentration. Concentrations of dissolved Fe, Al, Zn, Cu, and Mn significantly decreased, at p ≤ 0.05, from the inflow of the Delta to the distal reaches. Only Na, Mn, Fe, Al, and DOC showed significant differences, at p ≤ 0.05, along the local floodplain-channel hydrological gradients, with higher solute concentrations in the floodplains than the channels. Solute concentrations in soil water exhibited similar distribution patterns to those in surface water, but concentrations were higher in soil water. Based on the results, we hypothesise that floodplain emergent vegetation and the channel-fringing vegetation in the Panhandle (a fault-bounded entry trough to the Delta) and the permanently inundated eco-region together influence the cycling of solutes that enter the Delta through uptake.

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Published

2017-01-30

How to Cite

Keotshephile Mosimane, Eric Struyf, Mangaliso J Gondwe, Patrick Frings, Dimitri van Pelt, Piotr Wolski, Jonas Schoelynck, Jörg Schaller, Daniel J Conley, & Mike Murray-Hudson. (2017). Variability in chemistry of surface and soil waters of an evapotranspiration-dominated flood-pulsed wetland: solute processing in the Okavango Delta, Botswana. Water SA, 43(1 January). https://doi.org/10.4314/wsa.v43i1.13

Issue

Section

Research paper