Corporate Responsibility

Abstractions and low flows

Last reviewed:
About 70 per cent of our water comes from rivers, and the remaining 30 per cent from groundwater sources. Removing this water, a process known as abstraction, is regulated by the Environment Agency (EA) through its abstraction licensing process. During 2017/18, we achieved 99.97 per cent compliance with our daily abstraction licences.

Our compliance.

The table below shows our record of compliance with daily licences for public water supply (per cent) over the last five years:

  2013/14 2014/15
2015/16 2016/17 2017/18
Daily abstraction per cent compliance 99.91 99.89

Our partnership approach.

In some areas, abstracting water can contribute to low flows in rivers, which may be ecologically damaging. Last year we continued to work with the Environment Agency on our programme to investigate the risk of impact from abstraction on river flows, and reduce this risk where necessary.

Our joint approach starts with an initial investigation to understand the conditions in a river. If this shows that our abstraction is environmentally harmful, we carry out an options appraisal to assess possible solutions. These can include:

  • Reducing how much water we take.
  • Abstracting water at different times.
  • Supplementing the area with water from other sources.
  • River restoration that is designed to improve the health of rivers, which can involve improving habitat by narrowing sections of river or changing their course.

Our work in action.

Last year we installed an eel protection screen at our large intake where we abstract water from the River Thames at Hampton. This screen will help to protect eels from being drawn into our reservoirs, and help the recovery of the endangered eel population. Click on the link below to learn more:

In the past we’ve investigated the effect of our abstractions from the River Thames - both on the lower freshwater part of the river, and in the tidal estuary. We found that during periods of low flow in the upper tidal section, the level of oxygen in the water can reduce, affecting the aquatic life in the river. We’re now investigating what we can do to mitigate this impact by increasing the levels of oxygen in the effluent from Mogden sewage treatment works during these low flow periods.

Abstraction Incentive Mechanism.

We’ve recently been implementing a new measure to try to minimise the impacts of taking water at a number of our abstraction sites. This measure is called the Abstraction Incentive Mechanism (AIM). It’s designed to encourage water companies to reduce the perceived impact of water abstraction at environmentally sensitive sites, and it aims to complement existing management tools like National Environment Programme (NEP), Sustainability Reductions and Hands Off Flows on abstraction licences.

Implementing AIM doesn’t affect the security of our water supplies, and it doesn’t require any capital investment. We’ve implemented AIM at sites where we can use an alternative source of water when flows get low in the associated watercourse.

We’ve agreed 5 AIM sites with Ofwat and the Environment Agency. These sites are:

  • New Gauge - River Lee.
  • Pann Mill - River Wye.
  • Axford - River Kennet.
  • North Orpington - River Cray.
  • Pangbourne - River Pang.
Last year we complied with AIM at each of these sites.

Our future plans.

Building on work which we completed in 2016/17, we’ll be implementing the following measures at three of our treatment sites:

  • Pann Mill: We’ve agreed with the Environment Agency that we’ll reduce the licence before March 2020, and transfer part of it to Medmenham near the River Thames. We’ll then increase the amount of water we transfer from this source to High Wycombe.
  • Childrey Warren: We’ll close this source to provide a sustainable solution for the Letcombe Brook. Allowance for this is included in our Water Resources Management Plan (WRMP) and Business Plan. Design work will be completed this summer, followed by archaeological investigations, and construction will begin early next year.
  • Waddon in south London: We’re carrying out an options appraisal which will be completed in summer 2018.

In 2015 we started investigations on the Lower Lee and the River Chess at Chesham, to see if our abstractions are having an adverse impact on the environment. We’ve now completed these investigations, and concluded that we don’t need to reduce abstraction on the River Lee. But we’ve made an allowance for potentially reducing abstraction at Hawridge in the Chess catchment, and we’ll aim to complete an options appraisal for this in 2018.

Last year we started similar investigations on the Upper River Darent, where we found that no reduction in abstraction is needed, but an options appraisal is required. We’ve also undertaken investigations into abstractions in the River Cray catchment, where we’ve drilled some new observation boreholes, and we’ll complete this investigation by the end of 2018.

We’re also planning river restoration at eight sites across our supply area, and we’ll be doing river restoration works on the Amwell Magna Fishery and the Oxford Watercourses in summer 2018.