Home - Themes - Preserve water quality - Standardised methods to define pressures


    -Paul Michelet\Rhin-Meuse water agency
    "If we are to restore aquatic environments to good status as required by the Water framework directive and in compliance with the public policies adopted in France, we must of course learn more about and monitor water quantity and quality, but also take action againstthe factors causing the degradation..."

Standardised methods to define pressures

To assist the various water stakeholders in updating the status reports for 2013,Onema and its partners drafted and distributed a manual presenting the methods available to characterise the pressures weighing on water bodies.The tools to describe hydromorphological alterations and nonpoint-source pollution were finalised in 2012 and subsequently implemented throughoutthe country. alterations and nonpoint-source pollution were finalised in 2012 and subsequently implemented throughout the country.

To comply with WFD requirements, the updated status reports for all river basins must be finished by the end of 2013. One of the tasks is to describe the pressures weighing on surface waters and groundwater. This work was the source of many problems during the drafting of the first edition of the status report in 2004, due in large part to the insufficiently advanced methods and tools available at the time. To assistin characterising pressures,a manual presenting the methods available was drafted and distributed to all the concerned water stakeholders in February 2013. The manual is the product of a collaborative project launched in 2010 by the Ecology ministry with technical coordination provided by Onema.Other participants included the six Water agencies, the basin organisations and an array of research institutes (Inéris, BRGM,Irstea and INRA).


A manual presenting tools and methods

A dozen methods, organised by type of water body, were created or improved to describe four major types of pressure:
1) nonpoint-source pollution;
2) water abstractions;
3) industrial and urban pollution
4)hydromorphological alterations.
The Arpèges project, managed by Irstea and Onema,produced an indicator forthe risk of surface-water contamination by pesticides that then served to map the risks throughout France. In the proposed model,the risk of contamination is calculated by combining the vulnerability of surface waters and the pressure exerted by agricultural phytosanitary products. Another method concerning nonpoint-source pollution was developed by Irstea, in collaboration with Onema, to estimate nitrogen emissions from farms affecting continental water bodies. The estimate is based on excess nitrogen levels in soils using data supplied by the national NOPOLU tool in conjunction with a coefficientto determine transfer to water bodies. In 2012,the method was implemented throughout continental France and the results were made available to the river basins.

An analysis method based on geographic data

Another method presented in the manual is the Syrah tool that maps zones at risk of hydromorphological alterations which could result in failure to achieve good ecological status. Following several years of work,Syrah is now used throughout France by the Onema regional offices, the Water agencies and the regional environmental agencies. The purpose of the tool is to provide a consistent,standardised method, thus limiting field assessments. To that end, digital maps and data from national databases established by IGN and INRA, among others, were translated into surface data in order to analyse land use, development work and human activities causing alterations along the 230 000 km of rivers in continental France. Once plugged into the models, the data were then used in 2011 and 2012 by Irstea and Onema to establish pressure indicators, thus making it possible to compare the intensity of pressures and the risks incurred. On the basis of the various indicators, comparable overall risk assessments of hydromorphological alterations for each water body could be prepared for each river basin.

Indispensable collaboration between Onema and local stakeholders

Intense collaboration was required between the Onema regional offices, trained to use Syrah since 2007, and local, technical partners to obtain consistent and accurate results on the risks of physical alterations in hydrosystems. For example, in the Rhin-Meuse basin, a large number of coordination meetings were organised by Onema with the Water agencies and the regional environmental agencies on how to use Syrah.The meetings highlighted the usefulness of the method as a means to detect the risks of alterations rather than simply produce a status report. The discussions were also an occasion to explain how the data wereput together in order to produce the risk assessments. During the meetings, Onema also asked the local services to examine both the method and the results produced,the objective being to ensure that the risks detected using the Syrah data corresponded to the actual pressures observed in the Rhin-Meuse basin. To date, most of the evaluations are positive.