OR/14/047 European directives

Farr, G, and Hall J. 2014. Atmospheric deposition and groundwater dependent wetlands: implications for effective catchment management and future Water Framework Directive groundwater classification in England and Wales. British Geological Survey Internal Report, OR/14/047.

The habitats directive and conservation status

‘Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora’ more commonly known as the ‘Habitats Directive’ was adopted into UK law in 1992. The Habitats Directive contains a list of habitats in Annex 1 (e.g. ‘Humid Dune Slacks 2190) and then a list of species in Annex II (e.g. Liparis loeselii the Fen orchid). Some of the Annex 1 habitats and Annex II species may also be classed as ‘priority habitats/species’.

The main aim of the Habitats Directive is to promote the maintenance of biodiversity by requiring Member States to take measures to maintain or restore natural habitats and wild species listed on the Annexes to the Directive at a favorable conservation status, introducing robust protection for those habitats and species of European importance (http://jncc.defra.gov.uk/page-1374).

As part of the Habitats Directive each member state is required to report every six years on the conservation status of the listed habitats and species in the directive. This six yearly reporting is often referred to as ‘Article 17’ reporting and at the time of writing three rounds of this reporting have been undertaken. Each Annex 1 habitat or Annex II species is given a conservation status for example ‘unfavourable’ or ‘favourable’ based on the various individual and combined pressures that can contribute towards a GWDTEs condition assessment. Common Standards Monitoring is the standardized way to provide site specific condition assessment for SSSI and SACs (see JNCC, 2004) and depends upon a variety of condition components including presence and/or abundance of negative or positive indicator species.

Atmospheric nutrient deposition (although just one of many pressures facing GWDTEs) can have a wide ranging impact on the conservation status of designated sites (Emmett et al. 2011) including;

• change in habitat (and species composition) due to change in habitat structure and function
• loss or reduction of habitat size due to loss of species or actual habitat and potential reclassification as a different habitat (e.g heathland to acid grassland)
• and the cumulative deposition of nitrogen (N) building up within the soil

The water framework directive and groundwater status

As part of the WFD classification the chemical and quantitative status of each groundwater body must be assessed by applying a series of tests (UKTAG, 2012b). There are 305 individual groundwater bodies in England and Wales. The tests applied to each groundwater body include: ‘saline or other intrusions, surface water, groundwater dependent terrestrial ecosystems, drinking water protected areas, general quality and a water balance test’. The results are used to assign either ‘Good’ or ‘Poor’ status to each groundwater body.

The Groundwater Dependent Terrestrial Ecosystems test considers the impact of groundwater quantity (UKTAG, 2012a) and quality (UKTAG, 2012b) on the condition of the wetland. When a groundwater pressure such as over abstraction or elevated nutrients results in significant damage (Whiteman et al. 2010) the result is the failure of the WFD test, resulting in ‘Poor’ status for the surrounding groundwater body.

Two ‘cycles’ of groundwater classification have been undertaken in England and Wales (2008 & 2013). During each cycle the GWDTE test was applied to each groundwater body. During the first assessment the test was basic and this was due to a lack of site specific information, namely qualitative and quantitative hydroglogical data (water levels and water quality) and also a poor understanding of baseline water levels and water quality from comparable habitats.

The 2nd Cycle benefited from several years of investigation (e.g. Environment Agency, 2011 and SWS, 2010a/b), publication of several ‘Ecohydrological Guidelines’ (e.g. Environment Agency, 2010). The derivation of ‘Threshold Values’ for nitrate for a range of key wetland types that broadly conform to Annex I habitats (UKTAG, 2012a) also allowed more detailed assessment during the 2nd Cycle. The threshold values are empirically derived and are based on wetland condition (i.e favorable or unfavorable) and levels of nitrate within a WFD groundwater monitoring point hydrologically linked to a GWDTE. Threshold Vales were used to identify where rising trends of nitrate in groundwater bodies are likely to cause pressures in hydrogeologically connected GWDTEs. The threshold value methodology does acknowledge that atmospheric deposition is a source of nitrogen to GWDTE however no attempt is made to proportion the loading from terrestrial or atmospheric sources within the methodology.

The need to understand the contribution of atmospheric deposition v input of nutrients from the terrestrial environment is important to avoid Poor Status being assigned to a groundwater body, especially if atmospheric deposition is the main cause for unfavorable GWDTE condition. The need to ‘untangle’ and quantify the sources of terrestrial v atmospherically derived nutrients (source apportionment) is essential for successful application of the WFD. Understanding the sources of nutrient pressure is also vital when it comes to designing and implementing programs of measures (such as land management changes) to improve the status of GWDTE and ultimately the associated groundwater bodies. If we have not quantified the main source of the nutrients (e.g. atmospheric or terrestrial) then it is impossible to target actions to break the pathways to the GWDTE. The knowledge gap was recognised by the UKTAG wetlands task team and is the driving force behind this project.

Table 2 summarizes the results of the 2nd cycle WFD classification GWDTE test. Both chemical and quantitative data are shown for comparison, however it should be noted that quantitative failures are not linked to atmospheric deposition.

Chemical pressures at GWDTE resulted in the Poor Status classification of 6 groundwater bodies (2 in England and 4 in Wales). The remaining 303 groundwater bodies in England and Wales were classified as being in Good Chemical Status for the GWDTE test although 198 of these were classified as Good Status but ‘Probably at Risk’.

In comparison quantitative pressures resulted in the failure of 4 groundwater bodies, all in England reflecting the greater abstraction of groundwater in England than in many parts of Wales. No further discussion on the quantitative assessment is necessary for this report and the list of poor quantitative status groundwater bodies is supplied for information only.

Table 2    WFD Chemical and Quantitative Classification (2nd Cycle, 2013).
Groundwater bodies that have been assigned Poor Status due to pressures on a GWDTE

			Chemical Assessment
	ID	Groundwater Body	Status	Confidence	Risk
	GB41202G102100	South Cumbria Lower Palaeozoic and Carboniferous Aquifers	Poor		At Risk
England	GB41202G991700	Weaver and Dane Quaternary Sand and Gravel Aquifers	Poor	Low	Probably At Risk
Wales	GB41001G201300	Swansea Southern Carboniferous Limestone	Poor	High	At Risk
	GB41001G204200	Ynys Mon Central Carboniferous Limestone	Poor	High	At Risk
	GB41002G200400	Cleddau and Pembrokeshire	Poor	High	Probably At Risk
	GB41002G204600	Llyn & Eryri	Poor	High	At Risk
			Quantitative Assessment
	ID	Groundwater Body	Status	Confidence	Risk
England	GB40501G400500	Cam and Ely Ouse Chalk	Poor	Low	At Risk
	GB40601G501300	Basingstoke Chalk	Poor	Low	At Risk
	GB40601G602000	Regate Lower greensand	Poor	Low	At Risk
	GB40901G300800	Worcestershire Middle Severn	Poor	High	At Risk

Groundwater Bodies (GWBs) in Good Chemical Status can be further broken down into:

• 2 GWB’s in Good Status, High Confidence and At Risk
• 105 GWB in Good Status, High Confidence and Probably At Risk (of which 65 are considered probably at risk due to pressures on a GWDTE)
• 51 GWB in Good Status, High Confidence and Not At Risk
• 40 GWB in Good Status, High Confidence and Probably Not At Risk
• 4 GWB were considered Good Status, Low Confidence and At Risk
• 5 GWB were considered Good Status, Low Confidence and Not At Risk
• 92 GWB were considered Good Status, Low Confidence and Probably Not At Risk

A total of 6 GWB were classified at ‘Poor Status’ as a result of the GWDTE test. It is perhaps more important to consider the number of groundwater bodies that are ‘Probably at Risk’. In England and Wales a total of 65 GWB were classified as Good Status but Probably at Risk, due to chemical pressures in the GWDTE test, their locations are illustrated in Figure 3. It is possible that as more data is collected that some of the Probably at Risk groundwater bodies may indeed be re classified as At Risk in future classification cycles.

Investigations carried out by the Environment Agency and Natural Resources Wales (Environment Agency, 2011 and SWS, 2010a/b) highlighted that nutrient pressures were a key source of unfavourable condition at many GWDTEs, resulting in poor status for associated groundwater bodies.

File:OR14047fig3.jpg

Figure 3    WFD groundwater bodies At Risk (red) and Probably At Risk (orange) due to pressures at designated groundwater dependent terrestrial ecosystems in England and Wales (2nd Cycle).
Contains OS data © Crown Copyright and database right [2015].