Rantos AG opined (no English text is as yet available and, judging by recent practice, many never be available) yesterday in Case C-525/20 Association France Nature Environnement v Premier ministre, Ministre de la Transition écologique et solidaire.
The case turns on the issue whether the Water Framework Directive (WFD)’s core obligation for Member States not to cause water quality deterioration, implies that in their permitting systems, the Member States must not tolerate any such deterioration, even if it is temporary, unless the restrictive conditions of the WFD’s exceptions regime apply.
French implementation measures allow permitting outside those conditions if deterioration is temporary.
The Water Framework Directive 2000/60 aims at establishing
a framework for the protection of inland surface waters, transitional waters, coastal waters and groundwater which (a) prevents further deterioration and protects and enhances the status of aquatic ecosystems […] (b) promotes sustainable water use based on a long-term protection of available water resources; (c) aims at enhanced protection and improvement of the aquatic environment, inter alia, through specific measures for the progressive reduction of discharges, emissions and losses of priority substances and the cessation or phasing-out of discharges, emissions and losses of the priority hazardous substances; (d) ensures the progressive reduction of pollution of groundwater and prevents its further pollution, and (e) contributes to mitigating the effects of floods and droughts […]. (Article 1).
The AG kicks off by quoting the first recital of the WFD, that ‘Water is not a commercial product like any other but, rather, a heritage which must be protected, defended and treated as such.’
The point of entry for acceptable deterioration in water body quality, are Article 4 paras 6 and 7, worth recalling in full:
6. Temporary deterioration in the status of bodies of water shall not be in breach of the requirements of this Directive if this is the result of circumstances of natural cause or force majeure which are exceptional or could not reasonably have been foreseen, in particular extreme floods and prolonged droughts, or the result of circumstances due to accidents which could not reasonably have been foreseen, when all of the following conditions have been met:
(a) all practicable steps are taken to prevent further deterioration in status and in order not to compromise the achievement of the objectives of this Directive in other bodies of water not affected by those circumstances;
(b) the conditions under which circumstances that are exceptional or that could not reasonably have been foreseen may be declared, including the adoption of the appropriate indicators, are stated in the river basin management plan;
(c) the measures to be taken under such exceptional circumstances are included in the programme of measures and will not compromise the recovery of the quality of the body of water once the circumstances are over;
(d) the effects of the circumstances that are exceptional or that could not reasonably have been foreseen are reviewed annually and, subject to the reasons set out in paragraph 4(a), all practicable measures are taken with the aim of restoring the body of water to its status prior to the effects of those circumstances as soon as reasonably practicable, and
(e) a summary of the effects of the circumstances and of such measures taken or to be taken in accordance with paragraphs (a) and (d) are included in the next update of the river basin management plan.
7. Member States will not be in breach of this Directive when:
– failure to achieve good groundwater status, good ecological status or, where relevant, good ecological potential or to prevent deterioration in the status of a body of surface water or groundwater is the result of new modifications to the physical characteristics of a surface water body or alterations to the level of bodies of groundwater, or
– failure to prevent deterioration from high status to good status of a body of surface water is the result of new sustainable human development activities
and all the following conditions are met:
(a) all practicable steps are taken to mitigate the adverse impact on the status of the body of water;
(b) the reasons for those modifications or alterations are specifically set out and explained in the river basin management plan required under Article 13 and the objectives are reviewed every six years;
(c) the reasons for those modifications or alterations are of overriding public interest and/or the benefits to the environment and to society of achieving the objectives set out in paragraph 1 are outweighed by the benefits of the new modifications or alterations to human health, to the maintenance of human safety or to sustainable development, and
(d) the beneficial objectives served by those modifications or alterations of the water body cannot for reasons of technical feasibility or disproportionate cost be achieved by other means, which are a significantly better environmental option.
In C-461/13 Bund für Umwelt und Naturschutz Deutschland eV the CJEU  reinforced Member States’ duty to prevent deterioration under the WFD, as well as the obligation to enhance water quality. In that case the Court further emphasised  that these are not “solely basic obligations, but that this also concerns individual projects” and  that it follows from that that “Member States are required— unless a derogation is granted— to refuse authorisation for an individual project where it may cause a deterioration of the status of a body of surface water or where it jeopardises the attainment of good surface water status or of good ecological potential and good surface water chemical status by the date laid down by the directive.”
In the Opinion at issue, the AG (26) emphasises the CJEU’s finding in C‑664/15 Protect Natur-, Arten – und Landschaftsschutz Umweltorganisation , itself building on C‑461/13 Bund für Umwelt und Naturschutz Deutschland  that A4(1)(a) WFD
does not simply set out, in programmatic terms, mere management-planning objectives, but imposes an obligation to prevent deterioration of the status of bodies of water that has binding effects on Member States once the ecological status of the body of water concerned has been determined, at each stage of the procedure prescribed by that directive and, in particular, during the process of granting permits for particular projects pursuant to the system of derogations set out in Article 4
While the WFD does not define ‘deterioration in the status of bodies of water’, the AG (29) refers to the CJEU already having held in C‑535/18 Land Nordrhein-Westfalen  that the DNA of A4 proscribes a low threshold for planning and other authorities to find that there is such deterioration:
as regards the criteria for concluding that there is a deterioration of the status of a body of water, it should be noted that it is clear from the scheme of Article 4 of Directive 2000/60, in particular Article 4(6) and (7), that a deterioration of the status of a body of water, even if transitory, is authorised only subject to strict conditions. It follows that the threshold beyond which breach of the obligation to prevent deterioration of the status of a body of water is found must be as low as possible
Ignoring temporary deterioration would (36) amount to a de minimis approach which finds no support in the WFD, as among others the use of the aforementioned words ‘even if transitory’ indicates. In the view of the AG, either scientific assessment shows that the dynamic nature etc of the water body means a specific project will not have a deteriorating impact, in which case it can be permitted at least viz the WFD standards, or the science shows that there will be deterioration, in which case the only get out of jail free card are A4(6) and (7)’s exceptions.
Clearly, if the AG is followed, in practice this may lead ‘project friendly’ science to tweak the data.