Water balance and infiltration in a seasonal floodplain in the Okavango Delta, Botswana

Ramberg, Lars; Wolski, Piotr; Krah, Martin

doi:10.1672/0277-5212(2006)26[677:wbaiia]2.0.co;2

Cited by 51 publications

(39 citation statements)

References 33 publications

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“…Seasonal variation in temperature and river discharge may or may not be coincident in timing. For example, inundation of much of the Pantanal wetland of Brazil takes place in the warmer months (Hamilton et al, 1996), whereas river flooding in the Okavango Delta in Botswana coincides with the cool season (Ramberg et al, 2006). The Amazon River system drains catchments on both sides of the equator with roughly opposite seasonal discharge patterns and as a result the seasonality of discharge and floodplain inundation along the main stem is somewhat attenuated (Hamilton et al, 2002).…”

Section: Tropical River Hydrology and Climatic Regimesmentioning

confidence: 99%

Biogeochemical implications of climate change for tropical rivers and floodplains

Hamilton

2010

Hydrobiologia

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Large rivers of the tropics, many of which have extensive floodplains and deltas, are important in the delivery of nutrients and sediments to marine environments, in methane emission to the atmosphere and in providing ecosystem services associated with their high biological productivity. These ecosystem functions entail biogeochemical processes that will be influenced by climate change. Evidence for recent climate-driven changes in tropical rivers exists, but remains equivocal. Model projections suggest substantial future climate-driven changes, but they also underscore the complex interactions that control landscape water balances, river discharges and biogeochemical processes. The most important changes are likely to involve: (1) aquatic thermal regimes, with implications for thermal optima of plants and animals, rates of microbially mediated biogeochemical transformations, density stratification of water bodies and dissolved oxygen depletion; (2) hydrological regimes of discharge and floodplain inundation, which determine the ecological structure and function of rivers and floodplains and the extent and seasonality of aquatic environments; and (3) freshwater-seawater gradients where rivers meet oceans, affecting the distribution of marine, brackish and freshwater environments and the biogeochemical processing as river water approaches the coastal zone. In all cases, climate change affects biogeochemical processes in concert with other drivers such as deforestation and other land use changes, dams and other hydrological alterations and water withdrawals. Furthermore, changes in riverine hydrology and biogeochemistry produce potential feedbacks to climate involving biogeochemical processes such as decomposition and methane emission. Future research should seek improved understanding of these changes, and long-term monitoring should be extended to shallow waters of wetlands and floodplains in addition to the larger lakes and rivers that are most studied.

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Section: Tropical River Hydrology and Climatic Regimesmentioning

confidence: 99%

Biogeochemical implications of climate change for tropical rivers and floodplains

Hamilton

2010

Hydrobiologia

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“…In this environment the classifi cation of the riparian plants as dry land species is ambiguous as the riparian zones are fed by shallow horizontal groundwater infi ltration from adjacent rivers and fl oodplains (Ramberg et al, 2006). The majority of woody species (trees, shrubs and lianas) which occur within these riparian bands in the island fringes of the Okavango Delta are probably able to tap this groundwater resource (Ringrose, 2003).…”

Section: Biomementioning

confidence: 99%

Species diversity of the Okavango Delta, Botswana

Hancock²,

et al. 2006

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In the Okavango Delta (about 28,000 km 2 ) the number of identifi ed species is 1,300 for plants, 71 for fi sh, 33 for amphibians, 64 for reptiles, 444 for birds, and 122 for mammals. The local occurrence of different species of these taxonomic groups in the Okavango Delta is mainly due to a hydrological gradient from permanent streams and swamps to seasonal fl oodplains, riparian woodlands, and dry woodlands. This level of species diversity is normal for the southern African region, and all analyzed aquatic groups are composed of ubiquitous species with an additional signifi cant proportion of species originating from northern, more tropical systems. Cyclical variations in climate over thousands of years have created a huge wetland complex in the upper Zambezi and Okavango Rivers during wet phases. This wetland complex has fragmented into the Okavango Delta and other large wetlands in Zambia during dry phases. There are no endemic species in the Okavango Delta while the Southcentral African wetland complex is a centre of endemism. Species diversity of the Okavango Delta is a consequence of this unique environment, with dynamic shifts in fl ooding patterns that in turn force constant changes in patterns of plant succession and dependent animals. Temporal variations in fl ooding also cause accumulation and sudden mobilization of nutrients which are readily used by well adapted plant species. As a consequence, locally high biological productivity occurs, which in turn results in high numbers of grazing mammals.

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“…The samples were immersed in 50-100 ml of distilled water and incubated at room temperature without direct sunlight. The supernatant of each sample was replaced without agitation every forth day for a period of 50 days in order to simulate the turnover rate of floodplain water determined earlier (Ramberg et al 2000). For the entire incubation period no visible growth of plant material was observed.…”

Section: Dissolution From Soilsmentioning

confidence: 99%

Nutrient Budget in the Seasonal Wetland of the Okavango Delta, Botswana

Krah

McCarthy

Huntsman-Mapila

et al. 2006

Wetlands Ecol Manage

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The nutrient (P and N species) and chloride budgets were investigated in a representative floodplain in the seasonal wetlands of the Okavango Delta, Botswana. A variety of sources of nutrients in the surface water were considered, namely ion species coming with the floodwater, those generated from dry floodplain soils and those from water-soluble dust deposition (both local and long-range sources). Concentrations of total-nitrogen and chloride in surface water were below 1 mg l À1 . Total-phosphorus concentrations were 0.05 mg l À1 , reflecting the oligotrophic character of the system. Dust deposition rates were highest for chloride at 2.44 g m À2 year À1 followed by 0.79 g m À2 year À1 for total-N, 0.40 g m À2 year À1 for ammonia and only 0.02 g m À2 year À1 for total-P, respectively. Chloride was derived primarily from long-range transport, while N and P species were of more local origin. Dissolution rates for these ions combined were calculated to be 3.9 g m À2 for the flooded area in the 1999 season and thus all dry deposits must be re-dissolved. The accumulation of dust deposits on dry surfaces and their subsequent dissolution causes 2-5 times higher concentrations of nitrogen, phosphorus and chloride with the onset of the flood, thus boosting the nutrient stock in the crucial phase of the onset of flooding. Chloride dissolved from dry soil surfaces and dust contributed approximately 40% to the overall floodplain budget. Although contributions from the soil surface and dust to the nitrogen and phosphorus pools of the floodplain are less prominent (with 10% of total), they nonetheless represent a significant source of nutrients in the entire system. Extrapolation to annually flooded swamps (10,000 km 2 ) indicates a maximum contribution of 40% for total-nitrogen and 60% for total-phosphorus from dust deposition on wet or dry surfaces to the nutrient pool of the water body.

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Water balance and infiltration in a seasonal floodplain in the Okavango Delta, Botswana

Cited by 51 publications

References 33 publications

Biogeochemical implications of climate change for tropical rivers and floodplains

Biogeochemical implications of climate change for tropical rivers and floodplains

Species diversity of the Okavango Delta, Botswana

Nutrient Budget in the Seasonal Wetland of the Okavango Delta, Botswana

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