Nitrate threshold values for groundwater dependent wetlands

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1 Nitrate threshold values for groundwater dependent wetlands Why new threshold values for groundwater dependent wetlands? Groundwater chemical threshold values for groundwater dependent wetlands are required for Water Framework Directive groundwater body characterisation and classification. We did not have such values during RBMP 1.

2 What is the aim of the new threshold values? To protect important wetlands from significant damage that is caused by nitrate pollution of the groundwater. Which wetlands are in scope The values will be applied to Natura 2000 and SSSI wetlands during WFD classification. A breach of the threshold value has no relevance to decisions on the designation of Nitrate Vulnerable Zones under the Nitrate Directive.

3 Who developed the new threshold values? UKTAG Wetland Task Team, on basis of observed UK data and literature information A technical, and peer reviewed, report that details the development is available on the UKTAG website.

4 What are the groundwater dependent wetland threshold values? Threshold values for 11 vegetation types The values are more stringent in upland settings, and less stringent in lowland situations, The values reflects the varying nutrient sensitivity of these broad wetland groups at differing altitudes. The UK conservation agencies have agreed that there is no likely significant effect to Natura 2000 / SSSi sites where the relevant standards have not been breached.

5 Altitude GWDTE category 1 Any (<175mAOD) (>175mAOD) altitude Quaking bog 18 4 Wet dune 13 Fen (mesotrophic) and Fen Meadow 22 9 Fen (oligotrophic and wetlands at tufa forming springs 20 4 Wet grassland 26 9 Wet heath 13 9 Peatbog and woodland on peatbog 9 Wetland directly irrigated by spring or seepage 9 Swamp (mesotrophic) and reedbed 22 Swamp (oligotrophic) 18 Wet woodland 22 9

6 How will we use the new threshold values? A. WFD Groundwater body Classification IF: Important wetland sites (Natura 2000 / SSSI) fail conservation objectives and the type of damage indicates that nutrient pollution could be the cause of the observed damage then: If a relevant threshold value is breached, we conclude that there is a risk that the observed damage is caused by the groundwater nitrate concentrations. This will result in a site specific investigation that aims to: confirm that the observed damage is predominantly caused by the groundwater nitrate concentration confirm that the nitrate pressure is predominantly transmitted via the groundwater body. Only where the investigation confirms that the unfavourable status is predominantly caused by the nitrate pressure from the groundwater body, we class the groundwater body as poor. B. Prevent or limit the inputs of pollutants into groundwater (Identifying problems at source)

7 What is the likely scale of the problem? The nitrate threshold value is not expected to be being breached at many important wetland sites. If we were to re-run the 2009 classification using the new thresholds, we would expect that 5% of the groundwater bodies in England (17 GWB s out of 314), 1% in Wales (2 GWB s) and less than 1% in Scotland (0 GWB s) would progress to the further investigation stage. The groundwater on which a wetland depends is typically confined to the area close to the wetland. Relatively high concentrations of nitrate can occur across a large part of a body of groundwater without posing a risk to a wetland.

8 For the purposes of developing the threshold values, the UKTAG evaluated 180 wetland sites. In Scotland, impacts related to groundwater nitrate concentrations were suspected at around 20% of 50 sites evaluated. However, these impacts were not considered significantly damaged. England around 25% of the 93 sites that were used in the evaluation were in unfavourable condition and exceeded the relevant nitrate threshold value and as a result several further investigations that are examining the relationship between nitrate pressure and wetland damage are under way.

9 What action is likely required? Action is likely to be only required in the vicinity of the wetland. Action should be designed to target the specific sources of nitrate pollution of the groundwater that affect a particular wetland. Action might typically consist of adopting best agricultural management practices, such as locating manure stacks away from wetland receptors and those designed to reduce losses of nutrients from farmland.