IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Water resources and hydroinformatics : Subsurface water and nutrient processing in a large river floodplain
Subsurface water and nutrient processing in a large river floodplain
Elevated nutrient export from large rivers draining agricultural regions in Europe and North America contribute to stream
eutrophication and development of large-scale hypoxia but in many areas, nutrient losses from basins may be
attenuated by floodplains. Studies at the floodplain of the Cedar River in Muscatine County, Iowa, USA, are revealing
that the degree of water and nutrient processing in a large river floodplain is highly variable and affected by floodplain
lithology, hydrology and land cover. At a floodplain savanna site, topography and lithology are dominated by a series of
sandy ridges and fine-textured swales typical of a natural meandering river floodplain complex. We observed that
groundwater quality varied systematically in the two settings, with aerobic, fresh groundwater located beneath sanddominated
ridges and anaerobic mineralized groundwater beneath fine-textured swales. Variations in groundwater
quality with texture and topography in the floodplain indicates hotspots of biogeochemical activity. During both non-flood
and flood periods, water and nutrient processing were dominated by vegetation and subsurface controls. During nonflood
periods, floodplain groundwater fluctuated in response to external forcing (stream stage variation and precipitation
input) and internal forcing (evapotranspiration). During flood periods, groundwater monitoring with logging geochemical
sondes indicated that groundwater biogeochemistry was very dynamic, changing rapidly in response to flood inundation.
Greater biogeochemical activity occurred in low swales compared to sandy ridges. Groundwater showed little evidence
of NO3-N loading despite flood inundation from high NO3-N water from the agricultural watershed, thus providing
evidence that floodplain sediments are effective N sinks. Logging of dissolved oxygen dynamics in floodplain
groundwater revealed substantial fluctuation in DO concentrations at daily and hourly scales, likely lined with water and
photosynthetic flux. Overall, our work is highlighting a biogeochemically active, spatially heterogeneous subsurface
environment present beneath the floodplains of large temperate river systems.
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Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Water resources and hydroinformatics
Date Published : 19/08/2015
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