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

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

3. 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

4. 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

5. 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

6. 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)

7. 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)

8. 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

9. 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)

10. 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?

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

12. Nitrate Time Bomb

13. Nitrate Storage in USZ

14. Nitrate trends in Chalk Aquifer
Observed
Modelled

15. Thank you