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| Titel |
Estimating nitrate emissions to surface water at regional and national scale: comparison of models using detailed regional and national-wide databases (France) |
| VerfasserIn |
R. Dupas, C. Gascuel-Odoux, P. Durand, V. Parnaudeau |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068916
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| Zusammenfassung |
| The European Union (EU) Water Framework Directive (WFD) requires River Basin District
managers to carry out an analysis of nutrient pressures and impacts, in order to evaluate
the risk of water bodies failing to reach “good ecological status” and to identify
those catchments where prioritized nonpoint-source control measures should be
implemented.
A model has been developed to estimate nitrate nonpoint-source emissions to surface
water, using readily available data in France. It was inspired from US model SPARROW
(Smith al., 1997) and European model GREEN (Grizzetti et al., 2008), i.e. statistical
approaches consisting of linking nitrogen sources and catchments’ land and rivers
characteristics.
The N-nitrate load (L) at the outlet of a catchment is expressed as:
L= R*(B*Lsgw+Ldgw+PS)-denitlake
Where denitlake is a denitrification factor for lakes and reservoirs, Lsgw is the shallow
groundwater discharge to streams (derived from the base flow index and N surplus in
kgN.ha-1.yr-1), Ldgw is the deep groundwater discharge to streams (derived from total
runoff, the base flow index and deep groundwater N concentration), PS is point sources from
domestic and industrial origin (kgN.ha-1.yr-1) and R and B are the river system and basin
reduction factor, respectively.
Besides calibrating and evaluating the model at a national scale, its predictive quality was
compared with those of regionalized models in Brittany (Western France) and in the Seine
river basin (Paris basin), where detailed regional databases are available. The national-scale
model proved to provide robust predictions in most conditions encountered in France,
as it fitted observed N-nitrate load with an efficiency of 0.69. Regionalization of
the model reduced the standard error in the prediction of N-nitrate loads by about
19
Hence, the development of regionalized models should be advocated only after the
trade-off between improvement of fit and degradation of parameters’ estimation has come
under scrutiny.
References
Grizzetti B., Bouraoui F., De Marsily G., 2008. Assessing nitrogen pressures on European
surface water. Global Biogeochemical Cycles; 22.
Smith R.A., Schwarz G.E., Alexander R.B., 1997. Regional interpretation of
water-quality monitoring data. Water Resources Research 1997; 33: 2781-2798.
Schwarz GE, Alexander RB, Smith RA, Preston SD. THE REGIONALIZATION OF
NATIONAL-SCALE SPARROW MODELS FOR STREAM NUTRIENTS. Journal of the
American Water Resources Association 2011; 47: 1151-1172. |
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