WFD and the disproportionality principle
A national scale assessment for diffuse pollution
mitigation in Scottish lochs
A J A Vinten , J Martin-Ortega , K Glenk , P Booth , B B Balana , M MacLeod , M Lago , D Moran , M Jones
1
1
2
1
1
2
3
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1
The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH
2
Scottish Agricultural College SAC, Kings Buildings, West Mains Road, Edinburgh EH39JG, UK
3
Ecologic Institute, Pfalzburger Strasse 43/44, 10717 Berlin, Germany
Email: [email protected]
1
Introduction
Methods
The European Water Framework
Directive (WFD) aims to deliver good
ecological status (GES), as defined by
local regulators, to Europe’s waters. It
calls for the use of economic tools and
principles. It prescribes Programmes
of Measures (PoMs) to fulfil
pre-determined environmental
objectives using the most
cost-effective combination of
measures.
National scale benefit estimation
Cost-Effectiveness Analysis (CEA) is
hence proposed as the general
framework for prioritising mitigation
measures. Importantly, however, the
WFD allows ecological objectives to
be derogated on the basis of
disproportionality of costs of
implementation relative to the social
benefits that GES provides. This
suggests the use of Cost-Benefit
Analysis (CBA). These two decision
making frameworks (CEA and CBA)
have been widely accepted and
adopted by most national guidelines
across Europe.
Marginal benefits of mitigation were derived from the choice experiment (CE) of Glenk et al. (2011). SEPA’s national water
environment characterisation data for Scotland (SEPA, 2005a,b) were used to estimate improvements in the ecological
status classification in WFD from baseline conditions by 2015. Respondents to a representative national scale survey
(n=432) were asked to repeatedly choose from options that reflected future improvements in WFD ecological status
category at a given cost (included to enable estimation of Willingness-to-Pay (WTP)), and a “no change/no cost” option. The
baseline condition was 25% of Scottish loch area at GES, the maximum improvement level was 81%. Marginal benefit
estimates were derived from choice model parameters, representing the additional benefits derived from a unit (1%)
increase in national loch surface area under GES by 2015.
Cost-effectiveness analysis and marginal mitigation cost curve
Estimated P loads to lochs as a function of land use were based on a national scale database (‘screening tool’; SNIFFER,
2007). Three marginal abatement cost curves were developed (arable, improved grassland, rough grazing) using information
from Haygarth (2003). A fixed proportion of the land cover in each land use area was assumed to be affected by each
measure in each catchment. Costs and effectiveness for mitigation of P export from sewage treatment works and septic
tanks were based on Overarup (2005). We also added an optional “mop-up” term, enabling sufficient mitigation of P load to
achieve GES on all lochs (£200/kg P/y using chemical treatment of Lochs to remove soluble P). The most cost-effective
combination of measures in each catchment was estimated by solving for an objective function minimising costs to derive a
target reduction in P load. To enable comparison with national scale marginal benefit estimates, the marginal cost curve
was derived by sorting for cost-effective mitigation in relation to the respective contribution of the loch surface area in a
catchment to the national total (in %).
Results
A simple definition of disproportionate costs can be derived from basic economic theory: resources should be deployed
such that the marginal costs of pollution abatement for a catchment equate to marginal benefits of improvement.
Abatement costs beyond this point can be considered as disproportionate. Figure 1 illustrates the principle for the case of
national scale diffuse pollution (P) mitigation in Scottish lochs.
The cost curve illustrated in Figure 1 has been
derived under consideration of a £200/kg P/y
default “mop-up” term to enable all lochs to
reach GES. 72% of the lochs were mitigated
proportionately at a cost of £5.7 m/y. The
cross over point was at £634/ha of loch. The
remaining 28% of loch area could be mitigated
at a (disproportionate) cost of £184.2m/y.
However, the way they should be
joined up in the specific context of the
WFD remains unresolved.
This research explores a novel
approach to linking CEA to
proportionality analysis to serve the
purposes of the WFD in practice at a
national scale.
Paper on this research
Vinten, A.J.A., Martin-Ortega, J., Glenk, K., Booth, P.,
Balana, B.B., MacLeod, M., Lago, M., Moran, D. & M.
Jones (2012). Application of the WFD cost proportionality
principle to diffuse pollution mitigation: a case study for
Scottish Lochs. Journal of Environmental Management 97,
28-37
References
Haygarth, P., 2003. Cost curve assessment of phosphorus
mitigation options relevant to UK agriculture. Report for
Defra Project PE0203
Overarup, 2005. Ofwat Water Framework Directive e
economic analysis of water
industry Costs Final Report
Scotland and Northern Ireland Forum for Environmental
Research (SNIFFER), 2007. Diffuse pollution screening tool
e Phase III. Project WFD 77
Glenk, K., Lago, M., Moran, D., 2011. Public preferences
for water quality improvements: implications for the
implementation of the EC Water Framework
Directive in Scotland. Water Policy 13(5), 645-662
SEPA (2009)
http://www.sepa.org.uk/water/river_basin_planning.aspx
Acknowledgements
Thanks to Scottish Government for funding this work
Disproportionate
mitigation beyond
this point
Figure 1 Marginal costs and benefits of achieving loch P mitigation: estimates at national scale. Any costs to the
right of the point where the marginal cost curve cuts the marginal benefit curve, are not proportionate.
Figure 1 also shows the sensitivity of the
disproportinality assessment to the precision of
WTP estimates. In all cases, diffuse pollution
mitigation costs were found to be
proportional with respect to SEPA’s target
compliance level of 67% of loch area in GES by
2015 (SEPA, 2009).
In the absence of “mop-up” mitigation (figure not shown), the marginal benefit line crossed the marginal cost curve at
£1500/y/ha loch. At this point, 61.8% of loch area is mitigated, at a (proportionate) cost of £1.6 m/y. A further 0.2% of loch
area could be mitigated, at a (disproportionate) cost of £0.5 m/y. Apart from other sources of uncertainty (upland P export
coefficients, benefits of GES for individual lochs as opposed to national scale average, cost estimates for mitigation), the
fraction of total loch area mitigated proportionally and the proportionate costs expended on this fraction are therefore
sensitive to assumptions about “mop-up” costs and to the precision of marginal WTP estimates for improvements in the
fraction of lochs at GES.
Conclusions
• The CEA/CBA framework described gives a basis for estimating proportionate costs for
mitigation of P pollution of Scottish Lochs
• Using national scale benefit information, expenditure on the mitigation of P pollution in
vulnerable loch catchments is found to be proportionate at least up to SEPA’s target compliance
level of 67% of loch area under GES by 2015
• Further work on local P export coefficients and local valuation/benefits transfer in the context of
WFD would be helpful to confirm this conclusion