Assessing the risk of surface water contamination in agricultural watersheds. Multiscale approaches using spatial modelling and multi-criteria analysis for decision support ; Évaluation des risques de contamination des eaux de surface sur des bassins versants agricoles. Approches multiscalaires par modélisation spatiale et analyse multicritère pour l'aide à la décision
You can manage bookmarks using lists, please log in to your user account for this.
Media type:
E-Book
Title:
Assessing the risk of surface water contamination in agricultural watersheds. Multiscale approaches using spatial modelling and multi-criteria analysis for decision support ; Évaluation des risques de contamination des eaux de surface sur des bassins versants agricoles. Approches multiscalaires par modélisation spatiale et analyse multicritère pour l'aide à la décision
Published:
[Erscheinungsort nicht ermittelbar]: HAL CCSD, 2013
Language:
French
Origination:
University thesis:
Dissertation, HAL CCSD, 2013
Footnote:
Description:
There is evidence that intensive farming practices applied in Europe since the 1960s are responsible for the degradation of certain ecosystems, and a reduction in the quality of surface and ground water. Excessive use of nitrogen-based fertilisers and pesticides have led to high concentrations of these substances being found in rivers, thus compromising raw drinking water sources. Soil erosion – caused by simplified crop rotations, feeding livestock on corn instead of grass, and the removal of elements such as embankments, trees, hedges, etc. – has been conducive to the transfer of these particles into surface water. The resulting turbidity has led to the clogging up of spawning grounds, with many negative effects on their biological quality. European and national public policies aimed at preserving water resources have not yet had enough time to make any real impact on the current situation, despite the European Water Framework Directive calling for certain objectives to be fulfilled as early as 2015. Water managers are now concentrating their efforts primarily on the protection of water abstraction sites, an initiative which requires a number of measures to be implemented. To analyse the effectiveness of these different environmental protection instruments (and, just as importantly, to convince farmers to adopt them) there needs to be a clear system of assessment applied at the appropriate spatial scale. Complementing existing approaches, this thesis will focus on the development of methods for carrying out territorial environmental analysis of farming activities. For our study, we used (i) a multicriteria analysis and modelling (ELECTRE) combined with a Geographic Information System (GIS) on a selection of small elementary watersheds (ranging in size from 2 km² to 5 km²). These were located in the Oir basin, in Lower Normandy Region, in northwest France, and the Auradé basin, in the hills of Gascony region, southwest. We also employed (ii) a spatial modelling approach (PIXAL) to represent agri-environmental risks. Applied to an environmentally-sensitive area (hills of Gascony region) of several thousand square kilometres, the PIXAL method involved evaluating agri-environmental risks through a combination of remote sensing and GIS. In both cases, we showed that choosing the most relevant criteria allows agri-environmental risks to be assessed at different organisational scales. Analysis at farm plot level (where decisions are made by stakeholders in the field) gives a representation of the elementary watershed. Pixel-based evaluation, using satellite imaging (Landsat TM5), provides a nested multi-aggregation view of different watersheds. These criteria indicate (1) the vulnerability of surface water (slopes on farm plots, connections between spatial objects – satellite mesh and parcels of land – and the hydrographic network, state of banks, role of embankments), (2) anthropological pressure caused by farming (land occupation by crop type and practices in use, and - within small watersheds - (3) the role of regulating certain improvements (protection of waterways using grass strips and riparian zones, limiting particle transfer with embankments downstream of parcels). Water samples were taken at around sixteen different sites, with the results in areas that our study had classed as at risk" indicating a level of particles that seemed to confirm. By applying multi-criteria plot-by-plot parameters to our spatial model, we were able to refine the results of analyses carried out over a larger area. Placing this study in perspective, coupling ELECTRE-style multicriteria analysis with a spatial model could be an effective way to improve analysis at different policy-making and territorial scales, as well as providing additional support where assessment needs to switch between those varying scales.