Evaluation of Effectiveness of AMP6 Catchment Management Schemes

Case Study

Severn Trent Water commissioned ESI, now part of Stantec, to evaluate the effectiveness of their current catchment management programme, which aims (over 25 years) to improve the raw water quality at public drinking water supply sites so as to reduce Severn Trent Water’s treatment costs and provide wider environmental and recreational benefits.


During AMP5 Severn Trent Water Limited (STWL) successfully delivered one of the largest programmes of catchment management investigations in the UK water industry at a cost of £1.8M.


In AMP6 STWL increased activity to 27 full-scale catchment management schemes. This programme represented a substantial additional investment and was strongly supported by stakeholders. The focus of the programme included delivering metaldehyde product substitution schemes, a grant scheme for environmental improvement, and additional catchment based activities on the ground. The Drinking Water Inspectorate (DWI) has supported the metaldehyde programme.


As part of STWL’s PR19 work, the effectiveness of the AMP6 catchment management schemes need to be evaluated to see if:

  • the benefits assumed in AMP5 still apply, and the programme is on track to meet these,
  • the schemes should be carried on into AMP7 and what improvements can be made, and
  • whether the costs of the schemes need to be increased or decreased and what the balance of cost/benefit would now be.

The Project

ESI was instructed in November 2016 to analyse the available data (up to 1 December 2016), and to prepare an evaluation of the programme’s effectiveness focusing on the catchments to   22 drinking water sources – those with regulatory obligations (Environment Agency National Environment Programme and/or DWI Metaldehyde Undertaking).


Objectives included:

  1. Evaluate the AMP6 programme schemes in terms of effectiveness in delivering environmental, operational and financial benefits.
  2. Recommend improvements to the current AMP6 catchment management schemes and Outcome Delivery Incentive for implementation in AMP7. The catchment management programme implemented by Severn Trent was focussed on reducing the following at the 22 drinking water sources:
    – Metaldehyde (active ingredient in slug pellets)
    – Pesticides
    – Nitrates


This represented an ambitious programme, including both groundwater and surface water catchments across the whole of Severn Trent Water’s region (groundwater sources where nitrate is an issue are shown in the figure below).

Groundwater sources where nitrate is an issue


Flow of how engagement may influence change

ESI Change Diagram

The “change diagram” shows how engagement with farmers is anticipated to lead to changes in farm management, reduced concentrations of metaldehyde, pesticides and nitrates in rivers and groundwater and hence reduced treatment costs for Severn Trent Water and improved water quality for habitats and recreation sites.

The Outcome

20 months into the schemes, farmers on 30% of priority farms have been engaged by Severn Trent Water’s representatives in a positive way, and 80% of these (24% of the target farms) confirmed they have better knowledge of water quality issues in the catchment.


Severn Trent Water has also influenced many farms to change their farm operations for the benefit of water quality. For example, 20 months into the programme, 19% of metaldehyde target farms are participating in a metaldehyde reduction scheme and 7% of farms have taken up grants for infrastructure improvement, and for which farmers have contributed about 50% of the cost themselves.


Individual catchments were assessed against targets for farmer engagement, positive engagement and improved knowledge targets and then against changes in farm practice via farmers signing up for product (metaldehyde) substitution and Severn Trent Environmental Protection Scheme (STEPS) farm infrastructure grants – see example for the surface water catchment to the Staunton Harold reservoir (Melbourne, Leicestershire) below.

Engagement Progress Funnel

Other components of the scheme which indicate changes in behaviour include: farmers’ participation in pesticide amnesties, pesticide training and equipment testing.


Water quality data has been collated and reviewed. But, as anticipated, after only 20 months, there are insufficient data to make confident assertions about impacts on water quality.

“The reports were nicely structured and linked back to our original objectives – I liked the fact you converted the work into questions which were answered for each catchment.”
Dr. Katherine Filby, Catchment Management Planner, Severn Trent Water