WFD Trend Assessment: A UK perspective Rob Ward British Geological Survey Tim Besien Environment Agency

Overview RBC1 Trend Assessment RBC2 Trend and Trend Reversal assessment Comparison of methodology Lag time issues Future considerations

RBC1/RBC2 GWBs and substances? Trend assessment: considered for all GWBs at risk of poor status (for trend reversal objective) to support status assessment (saline intrusion and DWPA tests) to support characterisation of baseline Substances considered: all pollutants putting GWB at risk natural substances

Which data were used? All monitoring data from SM and OM (RBC1/2) SM data also used for natural trends (RBC1) Data over previous 10 year period Additional data from Water Cos (Article 7) used: as supporting evidence in RBC1 for trend analysis in RBC2 Additional expert judgement to evaluate data and trends

Statistical methods and data handling Statistical methods (Sens method, Mann-Kendall, Linear Regression) Test for statistical significance: 90% confidence Analysis of data from individual monitoring points: individual parameters and total pesticides 10 year period considered - must have: ≥10 measurements over a 4year period >20% of values must be >LOQ

Environmentally significant trends Trend must be statistically significant. Then…. Extrapolation of trends for 2 x cycles (12 y) Apply status tests with predicted concentrations/values (compare to TVs/GWQS) Where a predicted failure of one or more tests trend is considered environmentally significant Expert review (RBC2 only) Used to support classification (SI and DWPA tests)

Outcome 2009 2015 Scotland – 6 (RBMP2) N. Ireland – 5 (RBMP2) Upward trends (E&W) Outcome RBC1 RBC2 FAIL 81 102 PASS 223 207 2015 SUBSTANCE/GROUP No of GWBs NITRATE 70 METALS 33 CL_SO4_NA_EC 18 PHOSPHATE 14 SOLVENTS 8 AMMONIA 7 PHENOL 2 NA 1 PESTICIDES Status is a snap shot – trends dynamic situation Envronmentally significant trend – define Reversal – starting point 75% of GW QS or TV (default) or earlier if likely to fail EO withi 2 RBC. NO blue as have to prove up trend before reversal! WFD reporting/legal quirk! Mostly nitrate but some legacy pollutants as well. 6 in Scotland RBMP2 5 in NI Scotland – 6 (RBMP2) N. Ireland – 5 (RBMP2)

Software used 1st cycle bespoke software used – TIGER2 Enabled investigation of data/trend methods and sensitivity analysis 2nd cycle Aquachem (proprietary software) Outputs imported to GIS tool for QA, expert review and to support classification

Trend reversal assessment Only in RBC2 (2015) A light touch approach applied: due to lag times measures introduced in RBC1 unlikely to have reversed trends over short time period (one river basin cycle)   Did not identify any trends that had been reversed.   QA’d by area (local EA) experts (expert judgement)

Challenges Larger datasets – use of existing tools becomes harder Clearer criteria for determining when a trend is reversed (and reported) - what threshold to use? What priority should be given to measures: reverse trends or avoid deterioration? How should USZ lag times be factored in for identifying measures to reverse trends?

Depth to Water Table USZ velocity Chalk: 0.3–1.4 m/a Jurassic Lst: 0.6-2.5 m/a Sandstone: 0.6-1.3 m/a Porewater profiles Tracers, e.g. tritium

Nitrate Time Bomb

Nitrate Storage in USZ

Nitrate trends in Chalk Aquifer + Observed Modelled

Thank you www.bgs.ac.uk/research/groundwater