Reports and Documents

River Lark Pollution Review and Action Plan

The River Lark Catchment Partnership (RLCP) is working with a range of stakeholders to take stock of the declining state of the main river, focusing on the Lark upstream of Bury St Edmunds, downstream to Mildenhall.

Like all rivers in the UK, the Lark is facing a number of pressures to the so-called ‘quality’ of the water. The chemical measurements of quality are a surrogate for the ability of that watercourse to sustain the life expected of it, based on ecotoxicity data derived in controlled laboratory tests. Of course, the complexity of water chemistry means that aquatic life is exposed to a range of chemical stressors simultaneously, and which will differ daily, and within and between years due to weather and human influences. Unravelling the specific stressor and how it is linked to the state of the river ecology is challenging, and more so when the stressors are dynamic, and come from multiple sources across a river catchment.

Building the picture to identify the critical stressors, and attribute to sources, and pathways and ultimately the organisms within a river is possible, using the monitoring data from reliable sources such as regulatory investigation programmes, discharge quality assessments, modelling and mapping tools. Biological data, however, – freshwater invertebrate (and fish) communities, diversity and abundance – integrates the true state of the water chemistry where habitat is not limiting their ability to live, grow reproduce. To understand the state of a river, it’s the organisms that live within it that hold the key.

Whilst undertaking chemical analysis reliably is a costly and highly technical activity, conducted largely by scientists with high-tech analysers, it is notable that biological data can be gathered and analysed by trained citizen scientists, and volunteers, who can provide essential evidence of change over time. In this case, the trigger for this assessment has come from data from the Riverfly Partnership, which has shown a clear decline in invertebrate communities, and with some evidence of the decline of fish populations in reaches known previously to hold wild, natural spawning brown trout (Salmo trutta). These findings were made following three hot summers and where rainfall was less than average, creating ‘environmental drought and prolonged dry weather’ conditions (Environment Agency) which extended through the period 2018-2021. The resulting low summer flows and high temperatures would appear to be related to this ecological decline.

These findings were shared with relevant local partners in the autumn of 2021, at the time of the completion of the latest round of water industry investment (Asset Management Planning round 7 – AMP7) and the environmental improvement programme, Water Industry National Environment Programme (WINEP). Following a meeting with the Member of parliament for the Constituency of Bury St Edmunds, Jo Churchill, the stakeholder group comprising the Environment Agency, Anglian Water, The Rivers Trust, Norfolk Rivers Trust and the Riverfly Partnership committed to work together to develop an evidence base, from which an action plan would be developed to reduce risks to the Lark catchment. This stakeholder group was to be led by the River Lark Catchment Partnership, with support from:

  • Anglian Water
  • Environment Agency
  • Natural England  
  • CamEO Catchment partnership
  • Norfolk Rivers Trust
  • The Riverfly Partnership, and
  • The Rivers Trust

The purpose of this assessment is to:

  • Assess the current quality / state of the environment of the River Lark and its tributaries, against relevant benchmarks such as those set by Water Framework Directive and achieve Good Status
  • Identify the critical pressures on the environment, using best available evidence, and identify critical data gaps
  • Review the current regulatory measures and interventions being implemented to address the risks and pressures to the Lark catchment, and identify critical gaps in risk reduction measures necessary to achieve Good Status for the whole catchment.
  • Develop actions, forming an Action Plan, that can deliver effective responses to reduce risks, and address the underlying pressures
  • Inform relevant partners and stakeholders of the need for action, and enlist and gain commitment to deliver on those actions.

The approach to the study was to convene the group and to focus on two work areas – a catchment appraisal, and an assessment of the regulatory and non-regulatory responses to manage risks. Each workstream was conducted by independent working, with group discussions and presentations, taking place via Zoom calls at intervals to review the information being gathered, and set out next steps. Following these activities, a single workstream was formed to bring both elements together into a single evidence base, to underpin the action plan.

Critical to the review and assessment process was to identify all relevant pressures and treat them with balance. There has an initial focus on water quality and the main Anglian Water Water Recycling Centre (WRC) discharges, due to the timing of this review and the recent WINEP settlement. However, an equivalent amount of time has been devoted to diffuse rural and urban pollution to identify similarly the pressures, sources and impacts.

The review process has led to the development of two main outputs – a Catchment Appraisal (authored by Sam Hurst) and this report. The Catchment Appraisal will in effect be the basis for current evidence and be a living document into which new data will be added over time, to address both data gaps and maintain continuity with existing datasets.

This report on the River Lark Pollution Review and Action Plan is a snapshot of current and proposed interventions, and aims to set out a range of actions that the RLCP and its partners can take forward to reduce risks to the Lark, with the support of stakeholders. It is recommended that this report should have a life of two to three years where the actions should be reassessed in line with progress, environmental change, the development of the next water industry investment planning (PR24) and following the implementation of the much-anticipated Environmental Land Management Scheme (see recommendations)

River Lark Catchment Appraisal

Defining the problem of the Lark’s poor ecological health and pathways to improvement

The river Lark flows for 57km from its headwaters in on the eastern edge of the Newmarket ridge in Suffolk, to its confluence with the river Great Ouse near Littleport, in Cambridgeshire. The catchment covers an area of south of Bury St. Edmunds, flowing north west to Mildenhall. Here the Cut-off channel, a flood relief channel can divert water north to prevent flooding of Mildenhall and the low-lying fenland downstream. Below Isleham the Lark enters the South Level fenland drainage area, a pumped system, where water from the surrounding land has to be lifted into the embanked river. This report is primarily concerned with reaches of the Lark upstream of the cut-off channel that has the potential to support chalk stream ecology, The Lark and its tributaries above Mildenhall can be categorised 3 hydrological types;

1. Ephemeral winterbournes (Lark above Bury St Edmunds, Linnet, upper Cavenham stream, Kennet-Lee Brook)

2. Perennial chalk streams (Culford stream, lower Cavenham stream and Tuddenham Mill stream)

3. Perennial main chalk river – baseflow from groundwater provides year-round flow. Considered to be from below Fornham lock/Sheepwash bridge (B1106) next to the remains of Fornham Park Lock

The environmental drought of 2018-19 had a significant impact on river flow and highlighted the fragility of the Lark’s ecology in the face of mounting human and environmental pressures. The Lark is a historically degraded river but retains the potential to support flourishing chalk river ecology. The River Lark Catchment Partnership (RLCP) has been successful in delivering river habitat restoration projects through the Catchment Based Approach (Caba) however any ecological improvement is limited by both poor water quality and the impact of abstraction on natural flow. It is hoped that through this catchment appraisal the issues impacting the Lark can be better defined and communicated to key stakeholders in order to develop an action plan that will deliver outcomes to benefit the river Lark.

Chalk Stream Restoration Strategy

Chalk streams are an exceptional type of spring-fed river distinct to England and parts of France and Denmark. Although chalk exists in other parts of the world, nowhere else is there such a mass of it – the remains of an entire seafloor – exposed at the surface of the earth as rolling chalk hills, enfolding the clear-watered rivers we call chalk streams.

The English chalk downland gives rise to 283 distinct chalk streams as well as dozens of small, nameless rills and becks, comprising the vast majority of this river type to be found anywhere in the world. They are our equivalent to the Great Barrier Reef or the Okavango: a truly special natural heritage and a responsibility.

When rain falls on chalk hills it soaks down into the body of the rock and there undergoes a kind of alchemy, emerging from springs as cool, alkaline, mineral-rich water, equable in flow: the perfect properties to create a richly diverse eco-system.

Ecologically rich and biodiverse

Chalk streams in their natural condition are home to a profusion of life. Botanically they are the most biodiverse of all English rivers. For invertebrates, fish, birds and mammals, they offer a vast range of habitat niches. In Wessex they are a stronghold of our chalk-stream Atlantic salmon, now known to be genetically distinct. The upper ephemeral reaches, known as winterbournes, are global hotspots for a unique range of specialist plants and invertebrates.

Under pressure

But chalk streams are under immense pressure: they flow through one of the most urbanised, industrialised and farmed parts of the UK. Three chalk streams flow through London and there are many more in the chalk hills that surround the capital. Further afield, though many flow through more open countryside, that countryside is busily farmed, while villages or towns are sited somewhere along most chalk rivers. All these streams are impacted in one way or another by the activities of people.

We depend on chalk streams for public water supply, and have leant heavily on the resources of the underground body of water that feeds these streams. And yet every litre of water we take out of the aquifers – and we take billions and billions of litres to irrigate our crops, or run our taps – is water lost to the natural environment. Lost, that is, until we put it back. Only by the time we return water to these rivers it is no longer in the state in which we found it and has bypassed long reaches of the stream. It has passed through our sewage systems, becoming rich in nutrients and other pollutants. We may treat it, we may even treat it to a very high standard in some places, but in many others we do not. Routinely, we put back into these wonderful ecosystems water which makes them eutrophic, so that oxygen is sucked away from the river life which depends on it.

Even the water which we do not take out, which actually makes it to the underground aquifer or the stream, is unnaturally changed by human activities.

Our heavily farmed landscape exerts a huge pressure on water quality, either because rain runs off the land and along roads, accumulating harmful chemicals and nutrients along the way, or because it seeps down into the ground carrying with it the chemical fertilisers which have been applied to the land. There is now so much nitrogen in our chalk aquifers that we do not know how long it will take – even if we stopped applying nitrogen as fertiliser – for the aquifers to become clean again.

Finally, we have changed the rivers themselves, modifying them heavily over the centuries. We have used them for milling, for transport, to drive multiple agricultural and industrial revolutions. More recently, in the post-war decades, we made one of the most drastic and permanent changes of all: we dredged them. We took out the gravel river-bed – on which almost all chalk-stream life ultimately depends – and dumped it on the banks, all in an ultimately misguided attempt to drain the landscape.

Our challenge

So, we have a job ahead of us if we are to leave our wonderful chalk streams in a better state than we found them.

That is the challenge which this CaBA chalk stream restoration strategy will attempt to address – how to restore good ecological health to these unique rivers and the landscapes which support them.

CaBA is a space in which all stakeholders involved in the management, conservation and sustainable exploitation of our chalk streams can come together and agree on a way to achieve that goal. It is not always a comfortable space: NGO’s have to be pragmatic; water companies have to be idealistic; businesses, especially agriculture, have to adapt and be supported to do so: government has to listen and act.

This restoration strategy is what has come out of that discussion: an action plan which, if followed, will allow us to become proud custodians of 283 ecologically vibrant chalk streams from Dorset to Yorkshire, streams that may once more flow with a healthy flush of clean water through meandering channels over bright gravel, full of wildlife, beside which it is a pleasure to spend time and which could and should be a credit to the stewardship of our generation.

Download the Full Report:

Executive Summary: