These proposals for improving the quality of London’s rivers and water bodies are part of the London State of the Environment Report 2010.
The challenges pose a serious threat to water quality which will increase with climate change and growth. We all have a duty to protect and improve the quality of water in London for current and future generations. In order to achieve this, we must address the challenges in a sustainable manner and adapt to change.
Growth and development
It is clear that with the current rate of population growth, we need to make sure that the sewage network can cope.
Housing development needs to be in the right location with the right infrastructure, at the right time, to prevent a decline in water quality.
It is important that where growth demands increased capacity, adequate sewerage and sewage treatment infrastructure is provided in tandem with new development.
Development must not occur in locations where sewerage and sewage treatment facilities are inadequate in treating sewage to the standards required to protect the quality of the receiving watercourse.
We have been working closely with Thames Water to improve how they manage the risk to the environment from their sewage treatment works. As a result, there has been an improvement in Thames Water's sewage treatment works performance, and the planned Tideway Tunnels will help divert storm overflows to Beckton for treatment rather than discharge into the Tideway. See the Tideway water quality improvements case study for more information.
Under AMP4 and AMP5 (Asset Management Plans) some of London’s major sewage treatment works that discharge into the Thames Tideway will be improved to maintain this performance. Beckton, Mogden, Crossness, Long Reach and Riverside sewage treatment works will all be improved. Sewage treatment capacity at three of these sewage works will be increased to provide sufficient treatment and ensure they can cope with London’s growing population.
The planned London Tideway Tunnels will help divert combined storm overflows – the other main source of pollution – to Beckton for treatment rather than discharging into the Tideway.
Urban diffuse pollution
Diffuse pollution in London must be tackled now. The nature of the problem makes this a challenge but we can begin by promoting sustainable drainage systems, to reduce pollution from surface water run-off. We will need to work in partnership with local authorities, developers and communities to reduce diffuse pollution and manage its impacts. See the diffuse pollution report for England and Wales (PDF, 1MB).
Sustainable drainage systems (Suds) should be included in all new developments (a requirement under the London Plan policy 4A.14) at the earliest planning stage in order to reduce diffuse pollution. Suds should also be retrofitted to existing development, where appropriate. Suds can reduce and slow down run-off at the same time as improving water quality. Suds techniques include infiltration trenches, porous road surfaces, retention ponds and constructed wetlands.
In order to meet the requirements of the Water Framework Directive (WFD) all surface water bodies must achieve ‘good’ ecological status or potential by 2027. Much better control of diffuse pollution is required in order to realise this. River Basin Management Plans have been compiled for each water body to assess the risks and outline the programme of measures required to tackle any problems and meet the objectives of the Directive.
Sediment deposition requires long-term solutions in order to achieve a sustainable outcome. Long-term sediment management is currently under review but the options are increasingly costly.
In early 2009 we completed a project to dredge and remediate around 30,000 tonnes of sediment from the River Lee navigation between Tottenham Lock and Old Ford. For further details see the Lower Lee case study. We have also commissioned a study with the Water Research Centre, on the long-term management options for urban sediment within the lower lee catchment.
With the effects of climate change becoming ever apparent it is important that action is taken now. Changing weather will need to be taken into account when setting consents for sewage treatment works, to ensure that discharges don’t threaten water quality during periods of low flow. We all need to be adaptable to ensure we can tackle the challenges to water quality that are changing over time. This will only be achieved through effective liaison with key organisations.
More frequent and intense rainfall could lead to an increase in storm sewage discharges. The London Tideway Tunnel will help reduce the impact of such events on Tideway water quality by diverting the storm sewage away from the Tidal Thames to Beckton sewage treatment works for treatment, before discharge. See case study for more information.
See the Adapting to Climate Change in London strategy.