Modelling the impact of river morphology on nitrogen retention—A case study of the Weisse Elster River (Germany)

Abstract Denitrification is an important sink of nitrogen in riverine systems and mainly linked to interstitial sediments and hence to river morphology. Studies which quantify this relationship are rare. In this paper we analyse the effect of river morphology on nitrogen load of the 4th order river Weisse Elster (Germany). A modified version of the river water quality model WASP5 was applied to a 70.6 km river reach and measurements of the relevant water constituents were carried out for summer low-flow conditions. It was shown that nitrogen retention amounted to 23.4% of the nitrogen load of the upper boundary and benthic denitrification was identified as the largest contributor to that sink. The retention varies significantly along the river section with amounts being almost 2.4 times higher in a natural reach compared with a heavy modified and channelized river section. The mean denitrification rate was 189 mg N/(m 2  day). The impact of river structure restoration on nitrogen retention is relatively low. The model scenario representing the implementation of the most feasible measures can lead to an additional nitrogen load reduction of 5.4%.

[1]  P. Reichert,et al.  Identifiability and uncertainty analysis of the river water quality model no. 1 (RWQM1). , 2001, Water science and technology : a journal of the International Association on Water Pollution Research.

[2]  Gregory E. Schwarz,et al.  Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico , 2000, Nature.

[3]  Michael Rode,et al.  Multi-objective calibration of a river water quality model—Information content of calibration data , 2007 .

[4]  J. Nash,et al.  River flow forecasting through conceptual models part I — A discussion of principles☆ , 1970 .

[5]  Elizabeth W. Boyer,et al.  Nitrogen retention in rivers: model development and application to watersheds in the northeastern U.S.A. , 2002 .

[6]  R. Wayne Skaggs,et al.  Nitrogen Removal in Streams of Agricultural Catchments—A Literature Review , 2007 .

[7]  A. Hill,et al.  Hyporheic zone hydrology and nitrogen dynamics in relation to the streambed topography of a N-rich stream , 1998 .

[8]  S. B. Surman,et al.  Comparison of microscope techniques for the examination of biofilms , 1996 .

[9]  Randall E. Williams,et al.  Least-squares calibration of QUAL2E , 1992 .

[10]  B. Rhoads,et al.  Influence of geomorphological variability in channel characteristics on sediment denitrification in agricultural streams. , 2006, Journal of environmental quality.

[11]  Michel Detay,et al.  River bank filtration: modelling of the changes in water chemistry with emphasis on nitrogen species , 1997 .

[12]  Michael Kornaros,et al.  Kinetic modelling of Pseudomonas denitrificans growth and denitrification under aerobic, anoxic and transient operating conditions , 1998 .

[13]  M. Salehin,et al.  Relative roles of stream flow and sedimentary conditions in controlling hyporheic exchange , 2003, Hydrobiologia.

[14]  M. Salehin,et al.  Hyporheic Exchange with Gravel Beds: Basic Hydrodynamic Interactions and Bedform-Induced Advective Flows , 2004 .

[15]  Colin S. Reynolds,et al.  The ecology of freshwater phytoplankton , 1984 .

[16]  M. D. McKay,et al.  A comparison of three methods for selecting values of input variables in the analysis of output from a computer code , 2000 .

[17]  M. Poulin,et al.  Exchanges at the sediment-water interface in the river Seine, downstream from Paris , 1995 .

[18]  D. Rosgen.  Applied River Morphology , 1996 .

[19]  C. Willmott.  Some Comments on the Evaluation of Model Performance , 1982 .

[20]  G. Billen,et al.  Isotopic composition of nitrate-nitrogen as a marker of riparian and benthic denitrification at the scale of the whole Seine River system , 2003 .

[21]  F. Triska,et al.  Numerical modeling of coupled nitrification-denitrification in sediment perfusion cores from the hyporheic zone of the Shingobee River, MN , 2003 .

[22]  H. Behrendt,et al.  Nitrogen and phosphorus emissions from soil to surface water in the rhine and elbe basins , 1999 .

[23]  J. Lawrence,et al.  Development and structure of microbial biofilms in river water studied by confocal laser scanning microscopy , 1997 .

[24]  François Birgand,et al.  Quantification and Modeling of In-Stream Processes in Agricultural canals of the lower coastal plain , 2000 .

[25]  Arthur H. W. Beusen,et al.  Global modeling of the fate of nitrogen from point and nonpoint sources in soils, groundwater, and surface water , 2003 .

[26]  O. Berglund.  Periphyton density influences organochlorine accumulation in rivers , 2003 .

[27]  Lars Peter Nielsen,et al.  Nitrogen transformations in microenvironments of river beds and riparian zones , 2005 .

[28]  J. Böhlke,et al.  Reach‐scale isotope tracer experiment to quantify denitrification and related processes in a nitrate‐rich stream, midcontinent United States , 2004 .

[29]  Pattinson,et al.  Denitrification in river sediments: relationship between process rate and properties of water and sediment , 1998 .

[30]  A. Hill,et al.  Denitrification rates in relation to stream sediment characteristics , 1985 .