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abstract 547

Coupled water and nutriment modelling of an intermittent French river: The Vène

Author(s): Nanée Chahinian, Marie-George Tournoud, Jean-Louis Perrin, Bernadette Picot
HydroSciences Montpellier UMR CNRS-IRD- UM1-UM2, Université Montpellier 2, Case courrier MSE, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France. Tel : +33(0)4 67 14 90 21 Fax : +33(0)4 67 14 47 74 Email : chahinian@msem.univ- montp2.fr

Keyword(s): Modelling, Hydrology, Water Quality, Nutrient

Article:

Poster:

Session: OS5f Governance of water quality

AbstractIntermittent rivers have a specific hydrological behaviour resulting in long draught periods

interrupted by floods of high intensity and short duration which also influence the water quality dynamics. Indeed

during low flow periods pollutants accumulate in the river bed and are flushed away by the first floods. The stream’s

water quality will thus by governed by the interaction between the hydrological conditions of the river and its

chemical and biological status.
These rivers are widespread in semi-arid countries and the temporal and spatial

variability of their flows induce great management problems. They are also difficult to model because sharp variations

in flow and river bed wetness are still not correctly represented in most models. In addition, errors on flow

simulation, especially during low flow periods, have direct repercussions on water quality simulations. However,

there is a great demand for models as they are good tools to predict the impact of management changes on both the

river and the downstream water bodies.
The objective of this work is to model the hydrological and water quality

dynamics of an intermittent river. The latest version of the Soil and Water Assessment Tool (SWAT 2005) is used to

simulate phosphorous and nitrogen transport on the Vène experimental catchment for which data is available since

1994.
The results indicate that the model is sensitive to the prediction errors on flows and to the partitioning

between particulate and dissolved form for a given nutrient. The results also highlight the need for a better

representation of the channel rewetting processes.

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Coupled water and nutriment modelling of an intermittent French river: The Vène