Perspectives in handling uncertainty in European data

1. Perspectives in handling uncertainty in European data Philippe CrouzetEuropean Environment Agency (EEA)

2. Contents • Importance of uncertainty • Uncertainty in the assessment process • Uncertainty in the Policy questions proper • Two open questions, among others • Gross nutrient balances • Fragmentation of rivers • Example Response in the EEA work • Catchment – water relationships

3. data Other factors Processing Assessing data Monitoring Decision Other factors Implementing Measures Uncertainty in the data process

4. River fragmentation • Dams fragment rivers: • Large volume and residence time settle sediments, • Large volume modifies water regime • Wall jeopardizes fauna migration • 6700 large dams in Europe represent ~90% of stored volume (~1450 km3) and less than (??%) of walls • Fragmentation vs. fish is more uncertain than sediment trapping and water regime changes, but: • Actual reservoir volume? Current discharge pattern? • True commissioning year • Has dam a lake? • Are all dams properly located • Data base accuracy is key issue

6. Gross nutrient balances • Conceptual • GNB = Input {N} –output {N}, can be >0 or <0 • Negative values do not compensate positive values • Calculation scale and conceptual model issues • Large calculation areas are smoothed: problematic areas are faded, thus distorting results

7. GNB Sensitivity NUTS3 + CLC Ref (NUTS4 + CLC) Comparing catchments (298 units) surpluses by regression yields : S(dpt + CLC) = 0.94 S(ref) (R2 = 0.86) S(dpt) = 0.86 S(ref) (R2 = 0.82) Total surplus is comparable in the first case. NUTS3 alone

8. Implicit uncertainty in policies and assessment • EEA provides support to policy effectiveness assessment: • Has a given policy delivered expected results on the environment? • Were results observed at enforced time target? • Difficult questions are raised: • Is result defined? How expressing “meeting of the target” in accurate terms? • Can time the target is met be defined in variable conditions within compliance constraints? • Any response being “bound uncertainty”  “unbound uncertainty” • Making reliable assessment difficult and improvable

9. Analysis of the WFD specifications • Demands programme of measures: • to “prevent deterioration of the status” and achieve “good status... at the latest 15 years”, and “bring the bodies of water progressively to the required status”, • Following “coherent and comprehensive overview of water status”, and survey it • Through identification of “significant | main” pressures and • Assessment of status at the “water body type” level, minimizing the impact of seasonal variability ..... Reflect “...changes in the WB as a result of changes...” {pressures} • All terms pose practical and theoretical questions about their accuracy and uncertainty

10. Analysing trends • Stratified statistics were carried out considering: • Catchments as statistical population, (comprehensive) • Pressures through aggregates of land cover, population and livestock, defining strata in the catchments population, (significant pressures, WB types) • Nitrate, phosphate and ammonium developments with time (progressively) • On annual unbiased averages (...seasonal..) • To compute time trends and year of target meeting (achieve... at the latest...)

11. Sample results • Intra strata variability, • Inter-years variability • Source data uncertainty • Stratum uncertainty • Orphan strata assessment • Increasing uncertainty with reduction in size • Stationarity, linearity? • Reporting choices

12. Reporting uncertainties “Thickness of the line” Data dispersion frame Non compliant observations post target meeting

13. Towards conclusion... • Data related uncertainties now soundly addressed • Assessment related uncertainties are necessary for accurate policy assessment • They becomes considered at the assessment stage and addressed, but risk of shortage in data might make it inapplicable • Lack of understanding the uncertainty attached to complex systems of data, key to spatial assessment . Thanksfor your attention