The Use of Vegetation to Engineer Rivers for Water Quality and Ecological Status

Water resources in the UK and around the world are under increasing strain from the effects of population growth and climate change. Maintaining acceptable water quality, ecological conditions and security of supply in UK rivers is an increasingly energy intensive and expensive exercise. A significant increase in water treatment costs and carbon emissions are expected in order to meet increasingly stringent water quality legislation. There is therefore an urgent requirement for low energy techniques to improve water quality in rivers. This proposal utilises the unique expertise of the applicant in the field of environmental hydraulics, turbulence and mixing to propose a new scientific methodology by which vegetation induced flow structures (termed mixing layers) are utilised to optimise mixing rates in open channels, thereby causing a rapid reduction in peak concentrations of potentially harmful pollutants. This will reduce the ecological impact of discharges by the rapid reduction of chronic peak pollutant concentrations and provide alternatives to costly asset investment and the energy and chemical costs of additional treatment. This proposal will utilise the experimental facilities within the Pennine Water Group at the University of Sheffield to determine the optimum vegetation characteristics (type and configuration) required to engineer maximum water quality benefits. By proposing and developing advanced environmental fluid mechanics science in order to tackle engineering and societal challenges the proposal represents a step change in the development of a physically based, integrated approach to water management. The work will be conducted in partnership with key environmental stakeholders, and once the underlying science has been established the project will work with these partners to identify routes to implementation of the methodology in field conditions.

By developing techniques to use the physical properties of vegetation to rapidly reduce peak concentrations of pollutants in rivers and water bodies this proposal will mitigate rising energy and financial costs of water treatment and reduce environmental impact. Current methodologies of managing water quality by imposing increasingly strict controls on point discharge consents will become increasingly expensive in terms of energy, carbon and treatment costs as new stringent water quality legislation such as the Water Framework Directive is fully implemented. The proposal will allow more effective compliance with increasingly strenuous and sophisticated water quality legislation such as the Water Framework Directive. It is anticipated that this will also lead to a reduction in costs of treating abstracted drinking water in order to make it fit for human consumption. The primary beneficiaries of this aspect of the proposal are anticipated to be the UK water industry and its customers as well as other river stakeholders such as the Environment Agency, as well as to the environment itself. The continued supply of clean water is of critical importance for the UK economy. Pressures on water bodies are increasing due to the impacts of both climate change and increasing water demand; therefore work on sophisticated approach to water management has significant economic benefits for the UK.
There are also significant wider societal and economic benefits to improved water quality in natural water bodies and adoption of a more sustainable approach to water treatment and management. Better water quality leads to improved natural ecosystems and an increased recreational use of water bodies by the public. The value of fully functioning ecosystems has been highlighted by several recent reports such as the UK National Ecosystem Assessment (Defra, 2011). Only 26% of UK water bodies achieved good ecological status in 2009 (Water For Life, White Paper). This work therefore benefits environmental groups and members of society with interest in ecological health of water bodies (such as the Rivers Trust and Natural England), as well as the recreational users of waterways.