Water table fluctuations in the riparian zone: comparative results from a pan-European experiment

Abstract

Soil saturation is known to be of crucial importance to denitrification and other nitrogen cycling processes within the riparian zone. Since denitrification potential generally increases towards the soil surface, water table elevation can control the degree to which nitrate reduction is optimised. Given their topographic location and sedimentary structure, most floodplains are characterised by high water tables. However, detailed field data on water table levels, hydraulic gradients and flow patterns within the riparian zone are generally lacking. This paper presents data collected as part of a pan-European study of nitrate buffer zones, the Nitrogen Control by Landscape Structures in Agricultural Environments project (NICOLAS). An identical experimental design was employed at each site, allowing riparian zone hydrology and nitrogen cycling processes to be explored across a wide range of temperate climates; only the hydrological data are discussed here. A grid of dipwells at 10-metre spacing was installed at each site and manual measurements made at least once a month for a minimum of one year. In addition, at least one dipwell in each grid was monitored continuously using a data logger. All the riparian zones studied displayed a clear annual cycle of water table elevation, although other factors seemed equally important in influencing the range of variation. Where the riparian zone was flat, the water level in the adjoining river or lake proved more significant in controlling water table levels within the riparian zone than was originally anticipated. q

Development and application of the Riparian Mapping Tool to identify priority rehabilitation areas for nitrogen removal in the Tully - Murray basin, Queensland, Australia

“…The importance of riparian zone hydrology in influencing the extent of denitrification has been emphasised in many studies (e.g. Burt et al 2002;Rassam et al 2006).The classical conceptual model suggests that groundwater travels laterally and interacts with riparian sediments before discharging to the stream. This conceptual model for denitrification implies that a shallow water table intercepts the carbon-rich root zone, thus providing anoxic conditions.…”

“…The hydraulic conductivity of the floodplain plays a critical role. Burt et al (2002) reported that soils of medium hydraulic conductivities are most conducive to denitrification. Rassam (2005) conducted numerical modelling for coupled flow and solute transport and showed that soils with medium conductivities that range from 0.1 to 1 m day −1 are the most conducive to denitrification.…”

Modificación del índice de calidad de riberas: Inclusión del componente social en la evaluación de la calidad ribereña de la microcuenca del río Burío-Quebrada Seca

“…A lo largo de los márgenes del cauce de corrientes fluviales se encuentran franjas angostas de vegetación que pueden definirse como la interfase entre los ecosistemas acuáticos y terrestres (Burt et al, 2002;Granados, Hernández y López, 2006). A este tipo de comunidades vegetales que actúan como ecotonos se les conoce con el término de vegetación ribereña o riparia (Ceccon, 2003).…”

“…Por ejemplo, estas comunidades vegetales sirven de filtro entre el río y los ambientes adyacentes, lo que impide o retarda el flujo de la escorrentía hacia el cauce, la cual en muchas ocasiones trae consigo agroquímicos, nutrientes (principalmente nitrógeno y fósforo) y productos orgánicos provenientes de las actividades antropogénicas y de los cambios en los usos del suelo (Burt et al, 2002;Carlyle y Hill, 2001;Dhondt, Boeckx, Verdehoest, Hofman y Van Cleemput, 2006;Granados et al, 2006). También, permite amortiguar los procesos de sedimentación de los lechos de los ríos y de erosión en las riberas (González y García, 1998;Pinay y Decamps, 1988;Timoney, Peterson y Wein, 1997), poseen una gran influencia sobre la calidad del agua y del ecosistema fluvial, debido a que la vegetación, principalmente la arbórea, sombrea el cauce del sistema acuático y contribuye al control del nivel de insolación y del régimen de temperaturas de las aguas; además, aumenta la cantidad de oxígeno disuelto, regula la entrada de luz al sistema y retarda el crecimiento de las algas (Ahola, 1990y Dawson y Haslam, 1983, citados por González y García, 1998Granados et al, 2006).…”

It's sedimentary, my dear Watson : implications of watershed processes on the sediment fingerprinting approach

“…Soil in riparian zones tend to have both an overall higher moisture status due to proximity to the channel and a frequent change in redox conditions as a result of seasonal changes in the water table (Burt et al 2002;. Redox sensitive elements such, As, Cr, Cu, Fe, Mn, and U, are of particular interest, as the mobility of these elements within the soil profile are linked to the redox potential of the environment (Borch et al 2010).…”