Talk, 2nd International Hydrogeosphere User Conference 2011, Hannover: 2011-04-11 - 2011-04-13
Abstract:
The interaction between hydrological and biogeochemical processes within riparian wetlands significantly controls runoff generation, biogeochemical process settings and solute exports in many headwater catchments. Wetlands usually are characterized by shallow and surface near water levels. Under these conditions, where oxygen is limited to the uppermost 5‐10 cm the availability and spatial distribution of electron acceptors for redox sensitive reactions (like e.g. nitrate or sulfate) is controlled by sub‐surface transport processes. Furthermore, export of solutes (like e.g. dissolved organic carbon (DOC) or nitrate) from many riparian wetlands often is affected by a complex runoff generation process where fast and slow flow components mobilize water with different sub‐surface exposure times and redox states. Often, relevant hydrological and biogeochemical processes within wetlands occur on a relative small scale within few meters but are of immense importance for the catchments runoff quality and quantity. To assess and represent the significance of such small scale effects on a larger scale is a difficult challenge for modelers. In this study an approach is presented where we try to represent small scale runoff generation processes and sub‐surface flow patterns, influenced and induced by a micro‐topography typical for wetlands, on a coarser scale using the rillstorage height feature of Hydrogeosphere (HGS). The rill storage height feature in HGS was implemented to account for retention of water due to surface vegetation or micro‐topography. For the purpose of this study, a set of different plot scale HGS models, with different grid resolutions and a planar surface with and without rill storage height variations, were set up and compared to a high resoluted micro‐topography model. Simulations show that important aspects of micro‐topographical induced runoff generation processes and sub surface flow patterns are being preserved for a coarser planar surface model if the rill storage heights are spatially non‐uniform distributed on top of the plain surface. The same technique of spatially distributed zones with different rill storage heights were later used to mimic effects of micro‐topography in a catchment scale model