Groundwater: hidden risks and rewards?

Author: Mark Fermor, Director, ESI Consulting

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Groundwater: hidden risks and rewards?
Groundwater flooding in Dorset

Too much or too little groundwater can have both environmental and economic consequences and must be therefore be treated with more respect and understanding.

Groundwater is a source of drinking water. It supports our rivers and wetlands and their plants and wildlife in the UK. However, when groundwater emerges at the surface it can cause significant and prolonged flooding. The challenge for hydrogeologists is to understand and manage this valuable resource and advise society on how to minimise the risks.

Groundwater: hidden risks and rewards?
Low flow studies

According to the UK Groundwater Forum, the average annual replenishment to the UK’s main aquifers is approximately seven billion cubic metres, three times the total abstraction of groundwater. Aquifers also store large volumes of water in the saturated zone, far more than in surface reservoirs. In fact, about 99 per cent of liquid freshwater is groundwater, but widespread lack of understanding of groundwater prevents the scale of this resource being recognised. Equally, as our recent work on the economic risk from groundwater flooding reveals, there is also a widespread ignorance of the significance of groundwater as a hazard, preventing adequate risk management response. Quite simply, the risks and rewards that groundwater offers will repay better appreciation many times over. It appears that, as hydrogeologists, we have not yet met the challenge of educating policy makers and public alike on the nature of this hidden asset and liability.

Groundwater provides the baseflow component of river flow; it is also the source of water abstracted at river intakes for public supply and other uses during dry periods. Because of the importance of maintaining river flows, several major schemes in England have been designed to pump groundwater into rivers during dry periods. There are also many other interactions between surface water and groundwater that need to be recognised if we are to move to sustainable catchment management principles with Defra’s proposals for a 25-year Plan for the Environment. To provide an example: enhanced recharge from infiltration SuDS significantly increases the available resource whilst reducing flooding. In this article we highlight the pressing need for hydrogeologists to contribute to the national debate by bringing a more holistic perspective.

Abstraction and the environment

Water utilities must meet their customer service obligations to protect water resources and achieve good status for public use through the Environment Agency’s AMP National Environment Programme, under the Water Framework Directive.

ESI has worked with Severn Trent Water Ltd (STWL) and other water companies for many years to identify the impact of abstractions on aquatic ecology and help maintain supply/demand balance.

We have investigated specific problem abstraction sites and, through careful measurement of flows, water quality, ecology and the application of leading edge science, developed robust flow targets for affected streams. The proposed abstraction reductions have been built into Water Resource Management and AMP submissions to OFWAT.

Agriculture

Farmers are also important abstractors of groundwater in some parts of the country. The potential impact on water resource at a local level can often bring regulatory disputes, especially on environmentally sensitive sites. The recent case at Catfield Fen in Norfolk is a clear example of this.

Catfield Fen

Groundwater: hidden risks and rewards?
Image: Save Catfield Fen

Farmer Andrew Alston had been allowed to abstract more than 90,000 cubic metres of water to irrigate crops each year since 1986. The Fen is a nature reserve within a site of special scientific interest (SSSI) and is part of the Norfolk Broads special area of conservation (SAC), Broadland special protection area (SPA) and Broadland Ramsar.

Following a renewal application the Environment Agency (EA) undertook a groundwater modelling assessment and initially concluded the proposed abstraction was sustainable. However, concerns had been raised about the fen acidifying and drying as far back as the 1990s. During the consultation, the Broads Authority and Natural England produced new evidence of increased pH acidity in the water. In response, The EA reversed its decision, concerned that abstractions would harm the protected areas.

 

 The cost of groundwater flooding

 Whilst conserving precious groundwater resources and minimising abstraction impacts are critical, so too is understanding and responding effectively when there is an excess – groundwater flooding. But groundwater flooding impacts have been less understood by industry, insurers and communities and largely ignored by the regulator due to lack of awareness and fragmented regulatory structure.

Groundwater: hidden risks and rewards?
Extract of GeoSmart map of the risk of flooding from all sources

ESI recently developed a preliminary economic analysis on the risk of groundwater flooding to property and infrastructure. This, combined with other flood risks, has now created the first ‘Flooding from All Sources’ dataset using advanced modelling techniques on a five-metre grid. The study revealed the average annual economic loss to property in England was some £530 million, between 14 and 41 per cent of total flooding impact.

ESI’s work demonstrates that groundwater is a greater hazard to property and infrastructure than surface water flooding, highlighting that those involved in planning and managing the risk should be referring to groundwater flood risk maps and modes of flooding, and the overall understanding of flood risk that has hitherto been missed. The central issue we believe is one of poor understanding, and so an education campaign on this matter is urgently needed.

By modelling the effects of all types of flooding we are now helping the regulator to recognise the need to increase the focus on groundwater science on a catchment basis. Our national modelling has revealed the scale of the problem, but also highlights very large uncertainties, and we present recommendations to resolve these (see: http://esi-consulting.co.uk/530m-hidden-economic-cost-groundwater-flooding-revealed/). This should also inform water management strategies for more sustainable catchment management within the aforementioned 25-year Plan proposed by Defra.

Climate change, supply and flooding

Climate change means that groundwater storage will become increasingly important. If the South East becomes drier, management responses – including increased development of infiltration SuDS and other increased seasonal use of groundwater and artificial recharge – can provide an adequate response. Our nation’s hydrogeologists provide world class expertise and can help to show how a move to sustainable catchment regulation, if adopted by Defra in the 25-Year Plan, to help to meet these challenges.

It is time to review our nation’s preparedness for future groundwater pressures, and it is also time to wake up to the opportunities our largest water resource provides. Both will make demands on hydrogeologists to communicate a better understanding of groundwater.

A fresh approach to sustainable catchment regulation, and increased funding for groundwater in catchment science, will yield excellent returns. Until we do, groundwater represents a hidden risk and reward.

 

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