Let’s think holistically to improve water quality
Emerging policy in the UK has made it possible to fundamentally change how we address environmental challenges from diffuse and point-source pollution, writes James Knightbridge, Mott MacDonald’s catchment management lead.
The UK water sector stands at a crossroads where it could head in a new direction and take a radically different approach to the management of rivers and waterbodies.
The relationship with European Union policy, abstraction reform and the identification of priority catchments by the Environment Agency (EA), the 25 Year Environment Plan of the Department for Environment, Food and Rural Affairs, along with its ‘Health and Harmony’ paper on the post-Brexit future of food, farming and the environment, all provide opportunities to promote and formalise when, and how, more novel and more green solutions could be implemented.
Specifically, the EA’s Water Industry National Environment Programme represents an exciting opportunity for the water sector to consider catchment and nature-based approaches to improve water quality while enhancing natural capital, delivering net gain for the environment and achieving value for customer money.
Drivers under this programme cover water quality, ecology and water resources management and as such the EA has gone to some lengths to encourage water companies to take holistic catchment approaches, considering multiple drivers, to identify solutions.
Besides catchment management solutions to meet water quality and ecological drivers, such as those under the European Water Framework Directive, there is a growing movement in the UK to consider environmental and social-based solutions to address wider catchment challenges. These solutions include:
- natural flood management – to reduce the risk of flooding by ‘naturalising’ flows at a catchment scale
- green prescription – using green space and nature-based solutions to enhance health and wellbeing
- sustainable drainage – systems, whether urban or rural, to manage water flows
- systems thinking – considering the operation of all systems and assets that have an impact on the water environment from source to sea
- water resources management – sustainably managing and storing water resources in a catchment
Sustainable solutions
Traditionally, these challenges have been addressed individually and often through hard engineering, off-the-shelf solutions, end-of-pipe treatment, concrete flood defences or new sources of water.
While such approaches are important for achieving regulatory compliance, in light of climate change, competing demands on our resources, anti-microbial resistance and emerging contaminants such as plastics, promoting a more holistic view – incorporating broader benefits such as provision for ecosystem services – is essential.
The industry and regulatory drivers pushing for greater innovation and collaboration provide opportunities for sustainable, catchment-focused solutions that will help to protect the environment and ensure resilient water supplies for the future.
Mott MacDonald is taking a leading role in developing holistic management solutions across the water sector; two of our projects in the UK exemplify this approach.
Wider catchment benefits
As part of the UK’s response to the European Drinking Water Directive, water supply companies are required to adhere to a drinking water standard of 0.1μg/l of any individual plant protection product (PPP) in treated water.
This formed the background to our study to understand the potential effectiveness of taking a holistic catchment management approach in the Ogston Reservoir catchment in Derbyshire.
To enable the effective identification of sources of PPPs in surface waters used for drinking water supply, and to make an appraisal of cost-beneficial measures to reduce concentrations, a robust methodology is required that considers the integrated nature of river catchments and their management.
Our comprehensive assessment of the costs and benefits showed that the water quality of the Ogston abstraction can be improved.
The most cost-beneficial option was shown to be PPP substitution, combined with giving advice to farmers on how to prevent contamination of soil and watercourses.
Not only did the study demonstrate water quality improvement but also the potential for wider catchment benefits such as water and erosion regulation and boosting amenity value.
Stakeholder-led approach
Phosphorus enrichment in waterbodies can increase the risk of eutrophication (excessive levels of minerals and nutrients) and can be detrimental to ecosystem health of the waterbody. Phosphorus is a common reason for waterbody failure to meet ‘good’ status under the Water Framework Directive.
The Watton Brook, a tributary of the River Wissey in Norfolk, has an overall ‘moderate’ Water Framework Directive status and ‘poor’ status for phosphate (as of 2016).
Source apportionment modelling estimates that over 40% of the phosphate derives from treated wastewater discharges, and 40% from agriculture in the catchment.
An enhanced treatment process at the largest wastewater treatment plant has been successful, but further reductions in phosphate are required to achieve ‘good’ status.
Given the significance of agricultural sources of phosphorus, and the cost of installing additional treatment, or optimising existing treatment, our study explored alternative integrated nutrient balancing solutions by taking a stakeholder and ecosystem services-led approach.
In line with the ‘polluter pays’ principle and the paid ecosystems services approach, catchment nutrient balancing can be considered when one sector supports others to change behaviours and implement measures to reduce phosphorus or nitrogen.
The results of the appraisal indicate that agricultural phosphorus reduction measures are a feasible means of reducing phosphorus load in the Watton Brook.
In fact, a catchment management approach could deliver multiple benefits for the local community by reducing levels of nitrate, ammonia and sediment, as well as phosphorus, in surface water and groundwater.
The opportunity for improving water quality derives from the relationship with other stakeholders engaged in environmental improvements in the catchment.
It is through collaboration between these wider stakeholders, which include the EA and local Rivers Trust and Catchment Partnership, that a systems-orientated approach to managing the catchment could be successfully developed and implemented.
Positive impacts
One of the greatest challenges in designing and implementing solutions for environmental and social benefit is recognition and acceptance of the uncertainty inherent in catchment management.
End-of-pipe solutions typically guarantee a pollutant reduction to within a specified limit, but often at high expenditure and carbon cost.
Alternative catchment solutions can boost ecosystem services and natural capital, with positive impacts on human health and wellbeing. There is a risk, however, that outcomes for a target quality metric are less certain or controllable.
The multiple benefits gained by catchment solutions may outweigh the cost of isolated breaches in standards, but for such an approach to be considered worthwhile by water companies, both regulators and society need to accept uncertainty on compliance and focus on the social and environmental outcomes.
This is an updated version of an article first published in the newsletter of the International Water Association’s Specialist Group for Diffuse Pollution and Eutrophication.
James Knightbridge has been invited to deliver a presentation on the Ogston Reservoir catchment study at the 19th IWA International Conference on Diffuse Pollution and Eutrophication (DIPCON 2019) at Jeju, South Korea.