Image Driven Hydrological Components-based Fish Habitability Modeling in Riparian Wetlands Triggered by Damming

Abstract. Dissolved organic carbon (DOC) exports from many catchments in Europe and North-America are steadily increasing. Several studies have sought to explain this observation. As possible causes, a decrease in acid rain or sulfate deposition, concomitant reductions in ionic strength and increasing temperatures were identified. DOC often originates from riparian wetlands; but here, despite higher DOC concentrations, ionic strength in pore waters usually exceeds that in surface waters. In the catchment under study, DOC concentrations were synchronous with dissolved iron concentrations in pore and stream water. This study aims at testing the hypothesis that DOC exports are mediated by iron reduction/oxidation cycles. Following the observed hydrographs, δ18O of water and DOC fluorescence, the wetlands were identified as the main source of DOC. Antecedent biogeochemical conditions, i.e., water table levels in the wetlands, influenced the discharge patterns of nitrate, iron and DOC during an event. The correlation of DOC with pH was positive in pore waters, but negative in surface waters; it was negative for DOC with sulfate in pore waters, but only weak in surface waters. Though, the positive correlation of DOC with iron was universal for pore and surface water. The decline of DOC and iron concentrations in transition from anoxic wetland pore water to oxic stream water suggests a flocculation of DOC with oxidising iron, leading to a drop in pH in the stream during high DOC fluxes. The pore water did not per se differ in pH. There is, thus, a need to consider processes more thoroughly of DOC mobilisation in wetlands when interpreting DOC exports from catchments. The coupling of DOC with iron fluxes suggested that increased DOC exports could at least, in part, be caused by increasing activities in iron reduction, possibly due to increases in temperature, increasing wetness of riparian wetlands, or by a shift from sulfate dominated to iron reduction dominated biogeochemical regimes.

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Hydroperiod changes as clues to impacts on Cache River Riparian wetlands

Wetlands ◽

10.1007/bf03161328 ◽

1996 ◽

Vol 16 (3) ◽

pp. 379-396 ◽

Cited By ~ 11

Author(s):

Katherine S. Long ◽

John M. Nestler

Keyword(s):

Riparian Wetlands ◽

Cache River

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Sulfur Cycling at the Surface Water-Groundwater Interface in Riparian Wetlands

10.46427/gold2020.1919 ◽

2020 ◽

Author(s):

G.-H. Crystal Ng ◽

Cara M. Santelli ◽

Carla Rosenfeld ◽

Aubrey Dunshee ◽

Daniel Kaplan ◽

...

Keyword(s):

Surface Water ◽

Sulfur Cycling ◽

Riparian Wetlands

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Influence of basin connectivity on sediment source, transport, and storage within the Mkabela Basin, South Africa

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-10151-2012 ◽

2012 ◽

Vol 9 (9) ◽

pp. 10151-10204 ◽

Cited By ~ 2

Author(s):

J. R. Miller ◽

G. Mackin ◽

P. Lechler ◽

M. Lord ◽

S. Lorentz

Keyword(s):

South Africa ◽

Best Management Practices ◽

Management Practices ◽

Drainage System ◽

Sediment Source ◽

Riparian Wetlands ◽

Valley Bottom ◽

Sediment Size ◽

Catchment Areas ◽

And Storage

Abstract. The management of sediment and other non-point source (NPS) pollution has proven difficult, and requires a sound understanding of particle movement through the drainage system. The primary objective of this investigation was to obtain an understanding of NPS sediment source(s), transport, and storage within the Mkabela basin, a representative agricultural catchment within the KwaZulu-Natal Midlands of southeastern South Africa, by combining geomorphic, hydrologic and geochemical fingerprinting analyses. The Mkabela Basin can be subdivided into three distinct subcatchments that differ in their ability to transport and store sediment along the axial valley. Headwater (upper catchment) areas are characterized by extensive wetlands that act as significant sediment sinks. Mid-catchment areas, characterized by higher relief and valley gradients, exhibit few wetlands, but rather are dominated by a combination of alluvial and bedrock channels that are conducive to sediment transport. The lower catchment exhibits a low-gradient alluvial channel that is boarded by extensive riparian wetlands that accumulate large quantities of sediment (and NPS pollutants). Fingerprinting studies suggest that silt- and clay-rich layers found within wetland and reservoir deposits are derived from the erosion of fine-grained, valley bottom soils frequently utilized as vegetable fields. Coarser-grained deposits within both wetlands and reservoirs result from the erosion of sandier hillslope soils extensively utilized for sugar cane, during relatively high magnitude runoff events that are capable of transporting sand-sized sediment off the slopes. Thus, the source of sediment to the axial valley varies as a function of sediment size and runoff magnitude. Sediment export from the basin was limited until the early 1990s, in part because the upper catchment wetlands were hydrologically disconnected from lower parts of the watershed during low- to moderate flood events. The construction of a drainage ditch through a previously unchanneled wetland altered the hydrologic connectivity of the catchment, allowing sediment to be transported from the headwaters to the lower basin where much of it was deposited within the riparian wetlands. The axial drainage system is now geomorphically and hydrologically connected during most events throughout the study basin. The study indicates that increased valley connectivity partly negated the positive benefits of controlling sediment/nutrient exports from the catchment by means of upland based, best management practices.

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