Go with the Flow

Science to help manage our lowland rivers, now and in the future

Highlights from the Lowland Catchment Research programme (LOCAR) Go with the flow

Institutions participating in LOCAR

British Geological Survey Centre for Ecology & Hydrology Imperial College London King’s College London Lancaster University The Open University Queen Mary, University of London University College London University of Birmingham University of Durham University of Exeter University of Nottingham University of Reading University of Worcester o with the flow Science to help manage our lowland rivers, now and in the future

Definitions

A river catchment is the area of land whose water drains into that river. A permeable catchment lies on porous rock, such as chalk or sandstone.

Groundwater is underground water in the cracks and pores of the saturated permeable rocks.

Aquifers are porous rocks (such as chalk) or loose material (such as sand and gravel) that are a major source of groundwater. Springs and rivers form where aquifers meet the surface.

The water table is the depth below which the soil or rock is saturated with water.

Hydrology is the study of the movement, distribution and quality of water. Hydrogeology is the part of hydrology that studies groundwater in particular.

A dry valley is a valley without a surface stream – water may move under the surface instead, through the permeable soils or rocks. Overview Alan Thorpe, Chief Executive of NERC

lthough there is a balanced with the needs of the chemicals and other pollutants already perception that water is environment. The EU Water in the ground. plentiful in Britain, it is a Framework Directive requires the UK Monitoring the movement of A scarce resource in some to maintain our rivers as healthy water through a permeable catchment parts of the country. While water is a aquatic habitats. To meet this requires significant resources. Our renewable resource, it is also finite. A challenge the whole landscape needs £10 million LOCAR programme growing population, with more to be managed in an integrated way – invested £5 million in installing and households and greater wealth, means acknowledging that what happens in running field research facilities in growing demand for water. one part of a catchment will affect three river catchments: a We must manage our water another. measurement network which is the resources sustainably, so that the Good water management must be envy of hydrologists and aquatic needs of people, industry and based on the best information. This is ecologists throughout the world. agriculture are where LOCAR comes in. The To exploit this infrastructure programme has allowed scientists to NERC brought together a multi- unravel the complexities of how water disciplinary team of around 75 and the material it carries move scientists and students, who studied through permeable different components of the complex catchments. Catchments path that water takes through like these provide much permeable catchments and have taken of the drinking water on the challenging task of bringing for England, but these components together to give a both ecosystems unique picture of how the system and our drinking functions as a whole. water are under The results are relevant to threat from government, regulators, fishermen, rising demand farmers, conservation groups, land for water, a and water managers, and local changing authorities. This booklet presents a climate and a fascinating review of what we have pollution ‘time learned: what happens to our water bomb’ from from rainfall to river. I hope you will agricultural enjoy reading it.

2 The Lowland Catchment Research programme (LOCAR) Introduction Ian Douglas, programme coordinator

arge parts of England depend the spaces in the chalk are filled with on underground water for water. But we found that much of the human use and for water moves extremely slowly at L agriculture. Winter rainfall greater depths, is influenced by large- percolating through permeable rocks scale geological structures and does like chalk and sandstone normally not always follow the direction of tops up aquifers and maintains the surface valleys. LOCAR research low flows of streams in summer, but found that this water may stay for in recent years some of these streams many years (40 or more in some have occasionally dried up. Changes places) in the rocks before it emerges in land use and agricultural practices in springs or seeps into rivers. This have altered the patterns of movement means that even if we stop applying of sediments and chemicals in the agricultural chemicals today, it may water, affecting fish, plants and other be decades before they no longer life in the rivers. enter rivers fed by groundwater. To understand how and why these Within each catchment there changes are happening and to work are pressure points that respond out better ways of managing the quickly and dramatically to change. interactions between land and water, One of these is in the active upper the LOCAR programme has layer of the stream bed where examined the workings of five biological and chemical changes lowland rivers, particularly the regulate stream chemistry. interactions between surface and In valley bottoms on chalk, groundwater and the interplay of groundwater returns to the surface in alter the water flow and trap plant and animal life with stream springs, seepages and upwellings. We sediments, changing the habitats of chemicals and sediments. shed light on the complex biological plants, animals and insects, altering LOCAR investigated how water and chemical changes that occur in fish movements and influencing enters, is stored in, and is discharged this zone, where groundwater and biodiversity. LOCAR has made us from rivers in three contrasting stream water mix. The nitrogen and realise how important river plants are permeable catchments on chalk or phosphorus compounds from in determining the chemical and sandstone: the Frome and Piddle in fertilisers and sewage effluent are ecological status of rivers. Biodiversity, Dorset, the Pang and Lambourn in transformed into new compounds, habitat and water quality are affected Berkshire and the Tern in Shropshire. particularly within the top 20cm of by channel maintenance for flood and The work involved the largest sediments on the stream bed. Some of fisheries management. LOCAR results programme of drilling boreholes for the nitrogen and phosphorus is cast doubt on the existing models that research ever undertaken in Britain. temporarily stored in these sediments are being used to manage catchments. Along with new geological mapping, and may be released gradually or in Thanks to LOCAR, we now have this revealed in more detail than bursts after storms. But some of the a good understanding of what before that chalk groundwater moves nitrogen and phosphorus, which controls groundwater movement in along different routes at different otherwise would have affected life in these catchments. Detecting the speeds. We have found that chemicals the river further downstream, is fixed sources of water will allow managers move from the land into streams in almost permanently to particles of to plan water-quality-control hours or days in some areas, yet take a sediment in the river. The greenhouse measures more precisely. decade or more in other parts of the gases nitrous oxide and methane are same catchment. In some places, also released to the atmosphere from water moves down sinkholes, through the stream bed. LOCAR found that openings in the rock to emerge at these streams may not be as healthy as springs a day or two later. Elsewhere conventional ecological assessments it flows through tiny cracks in the lead us to think. uppermost part of a zone where all In lowland streams, plants can

The Lowland Catchment Research programme (LOCAR) 3 Science highlights

How to recognise a healthy river

Most conventional biological many nutrients and their assessments of the LOCAR rivers, clogged-up beds emit based on the diversity and type of the significant quantities of animals and plants that live in them, gases such as methane and would conclude that they are nitrous oxide – not features ecologically healthy. But LOCAR of high quality river scientists identified significant ecosystems. The river function changes taking place in stream beds and conventional assessments which suggest that these rivers may seem to be telling different stories not be as healthy as previously and suggest we might need a new thought. Salmon and trout eggs ecosystem-based approach to survive poorly, the rivers contain too ecological assessment (see page 13). Sampling riverbed sediments in the River Tern.

The significance of plants

LOCAR scientists showed that critical for a complex and healthy plants are the engineers of a habitat in lowland rivers (see page 12). healthy river. Plants Land plants are also important for influence the speed of the rivers. LOCAR research showed that current, where sediments different types of plant cover in the are deposited and eroded, catchment have a big effect on the where nutrients are amount of rainfall reaching a river. recycled and where the Using new methods developed by animals of the river live. LOCAR (combining direct local Faster currents between measurements with satellite data), we dense patches of water found that much more rainwater weeds can clean silt from evaporates from fields of grass and river bed gravels. Where clover than from fields of wheat, for plants slow the current down, instance. Hedges, especially hawthorn, plant debris, organic and mineral intercept and evaporate more than half particles are deposited. As a result, of the rain that falls on them, and new bed and bank forms develop, woodlands and wetlands also affect the new plants germinate and grow, and amount of rain that gets into the rivers hotspots for processing organic and the ground. This information will matter are created. Sensitive be important in estimating how much management of vegetation in the rainfall is needed to recharge The Himalayan balsam. river and on its banks is therefore groundwater.

Agricultural chemicals will pollute rivers for years to come

A new LOCAR catchment model of chemicals applied, LOCAR found And even if there are reductions now, shows how river pollution will that some rivers will routinely exceed agricultural and other chemicals respond to changes in the application safe drinking water limits by 2020 already in the groundwater will of agricultural chemicals. Unless there and groundwater nitrate will continue continue to leach into rivers for are drastic reductions to the amount to increase for the next 70-80 years. several decades (see page 10).

4 The Lowland Catchment Research programme (LOCAR) Where does the water go?

In the Pang catchment, LOCAR discovered that much of the water researchers found that the flow of below the surface of the catchment water underground can’t always be flows directly into the Thames, not predicted by the slope of the land into the Pang as expected. Water surface, because groundwater flow is managers need to know where the controlled by the complex network of groundwater is going so that they can large and small cracks in the porous make the best decisions about how rock which developed over millions of much water can be extracted and how years. Using data from the dense these sensitive catchments will network of boreholes on the Pang respond to rainfall and pollution (see catchment, LOCAR scientists page 9). Data from boreholes allows hydrogeologists to map water movement underground.

An invisible water supply

Dry valleys, which are a feature and gravel on the floor of dry valleys, of permeable catchments, were feeding a considerable volume of formed by meltwater at the water into the main rivers. This end of the ice age when the invisible underground flow helps to land was frozen. LOCAR sustain aquatic environments during research in the Tern catchment droughts, but also channels found that water from aquifers agricultural chemicals into rivers (see flows through the layers of sand page 11).

Tracing the source of silt

Eroded soil can damage aquatic life by pasture to cultivation in southern silting up river channels. For example, England affects rivers. For the first time salmon don’t breed well when their we have a complete picture of where gravel spawning beds are silted up. eroded soil particles come from and go And silt can carry pesticides and to. LOCAR discovered that bank erosion nutrients into the water from fields. is only a minor source of sediments in River managers need to know where most of the study catchments: much of it the eroded sediment comes from so comes from agricultural land and that it can be controlled. LOCAR has particularly from ploughed fields. Very used innovative ‘fingerprinting’ little silt comes from unploughed Ploughed fields generate about two- methods to investigate the source of pasture. This important new thirds of the fine silt transported by the the fine sediment moving through the information can be used by River Pang and about half of it in the study catchments. environmentally sensitive Lambourn. The detailed field measurements farming initiatives to clearly showed that the shift from reduce silt in rivers.

Side channels are important for fish

It is not just the main channels of characteristics. LOCAR scientists rates change (see rivers which need looking after: found that different fish use different page 12). LOCAR research showed that side types of channel as refuges and for channels are very important for spawning, moving from one type of Radio tags allowed us to biodiversity and have different flow, channel to another at different times track fish as they move along sediment, vegetation and temperature of year and as water levels and flow and between different channels.

The Lowland Catchment Research programme (LOCAR) 5 Perspectives: is this research useful?

LOCAR research has many applications – for water and land managers, farmers, fishing clubs, wildlife and countryside organisations, local authorities, parish councils, planners, agricultural advisors, regulators and policy-makers. Here are some views on LOCAR research from the people and organisations that will use it.

Water for life contributing to HELP, the IHP us with a new appreciation of how Mike Bonell is the former Chief of Hydrology for the Environment, Life permeable, lowland catchments Section: Hydrological Processes and and Policy Programme, and the function and with invaluable scientific Climate within UNESCO’s associated IHP integrated science underpinning to help us develop the International Hydrological project.’ regulatory framework we need.’ Programme (IHP). As the chair of LOCAR’s steering committee he has Sustainable farming The water industry been active in promoting LOCAR Sheepdrove Organic Farm is on the Thames Water is responsible for within the IHP as an example of a Pang-Lambourn catchment studied supplying water to some eight million new integrated approach to by LOCAR. Measurements of customers in the south-east of catchment research. This approach is evaporation, groundwater and soil England. The company is investing needed to tackle the global problem moisture were made on the farm. Lois heavily to meet the increasing of supplying an increasing world Philipps (who works with Sheepdrove demands on the limited water population with clean, fresh water. at the Elm Farm Research Centre) resources available in the region. Mike said, ‘Water is crucial for said, ‘We were pleased to work with Brian Connorton of Thames Water sustainable development, and 2005 to the LOCAR scientists. At Sheepdrove said, ‘The low rainfall in the winter 2015 is the UN International Decade we appreciate that action on one part 2005-2006 has demonstrated the for Action Water for Life. The decade of a catchment may create impacts vulnerability of water resources recognises the need for integrated elsewhere. We need to know the in southern England to drought water resource management and connection between rain falling on conditions. In planning for the future, balancing the preservation of our the ground, and water in the water companies need to continue natural environment with the underground aquifers and in the with the progress being made in using alleviation of poverty and hunger. rivers. Only when we know how the water more efficiently, while at the LOCAR is a model programme – it catchment functions as a whole will same time identifying and developing has shown how scientists can work we be able to manage it to create a new environmentally sustainable yet together to provide water managers healthy environment: sustainable farm cost-effective water sources. LOCAR throughout the world with the management and sustainable water results are helping us to make these knowledge they need. In that regard, management go together.’ investment decisions based on sound LOCAR has a pivotal role in science.’ Regulating the environment Local communities The Environment Agency regulates Councillor Jeff Hopkins of Market how catchments are managed in Drayton has welcomed the way the England and Wales. The Agency’s LOCAR projects in the Tern Bob Harris has been following catchment have given the local LOCAR research to ensure that they community a new understanding of make full use of the results as soon as the significance of their local river. they appear. Bob said, ‘Our objective Jeff said, ‘Having such high-level is sustainable water use and healthy research going on in the community aquatic ecosystems. LOCAR is provides new information for all, changing the way we perceive lowland from farmers to schoolchildren. If it catchments – the processes helps them to use the land and water controlling water and pollutant more sustainably, it is a good thing.’ movement are far more dynamic than we had thought. LOCAR is providing

Sheepdrove Organic Farm.

6 The Lowland Catchment Research programme (LOCAR) Backdrop: the water crisis in southern England

A rising population, more households and greater wealth have led to an ever greater demand for water, putting the limited supply in the south of England under stress.

Thames Water, which is responsible for delivering water to London and much of south-east England, expects the number of households in its area to increase by 200,000 over the next ten years, with the population increasing by 800,000. Added to this, on average, each customer is also steadily using more water, creating a further new demand. Increasing demand for water puts pressure on the environment. Water companies could meet the demand by extracting more from rivers, but then the rivers would dry up – damaging the local ecology and environment. How will this demand be met? The south-east of England has a relatively low rainfall and probably Household water use. Each person in England and Wales 70 per cent of this is lost to uses an average of 154 litres of water a day - a figure evaporation by the crops and woods which continues to rise. which cover the landscape. The Source: Ofwat - Office of Water Services. remaining 30 per cent has to replenish our reservoirs and aquifers, and sustain our rivers and wetlands. because of the water stored The region is quite resilient to underground, but water supply summer droughts during the summer is vulnerable to dry winters. If winter rainfall is not sufficient to refill the aquifers and reservoirs, the water supply is at risk the following summer. The Low winter drought orders rainfall in 2005- 2006 caused the headwaters of the River imposed on the Pang to dry up completely. south-east of J o

h England during n

P r the summer of i o r

I m 2006 are a case in been banned. a g e s

/ point. The area This combination of increasing A l a m

y relies heavily on demand and limited supply will groundwater but inevitably lead to water shortages. To because of the dry avoid a crisis in the future requires winter of 2005-2006 action now: new policies, based on groundwater levels are sound science, are needed for at record lows and all planning, regulating and managing non-essential water use has the region’s water resources.

The Lowland Catchment Research programme (LOCAR) 7 The LOCAR approach

A permeable chalk or sandstone catchment is a complex, dynamic system with a multitude of interacting components. LOCAR was designed to unravel these interactions through a coordinated programme of long-term monitoring and 12 studies focusing on a part of the hydrogeology or ecology of one or more of three study catchments. Taken together these studies produce, for the first time, the ‘big picture’: a unique understanding of how the catchments behave as complete systems.

To understand how a permeable catchment works, LOCAR researchers needed to measure how much water falls on the catchment, how much is taken up and evaporated by plants, how much enters an aquifer and how it then moves through pores and cracks in the rock into the river. European law has changed the way that water resources are regulated by the Environment Agency. The European Water Framework Directive places a new emphasis on creating and maintaining rivers as healthy ecological habitats. To help the UK meet its requirements under this directive, LOCAR has investigated how sediments and chemicals (dissolved in the water or attached to sediment) move from fields into rivers. Identifying the key physical, Using a ground chemical and biological processes penetrating radar to measure the subsurface operating within a river valley has structure of the river bed. allowed the impact of land and river management on the ecology of the river to be assessed, one of the requirements of the directive. Infrastructure worth £5m was used in this research. At each of the geology into the rivers. three LOCAR catchments, the teams A computer model that put in equipment to measure the maps how water moves across rainfall and how much of it and through a catchment is the evaporates, refills the aquifers or is best method of combining the stored in the soil. Measuring the results from all the diverse studies chemical composition of the water from the LOCAR programme. revealed the water quality at each LOCAR is developing models which stage in the path from rain to river. A will be able to make useful network of deep boreholes was drilled predictions of how changes in one Aerial view of the River Pang. to allow the LOCAR scientists to component of the catchment system map the flow of water as it finds its will affect the quantity and quality of way through the complex chalk water in another (see page 14).

8 The Lowland Catchment Research programme (LOCAR) How water moves underground

Geological structure and history influence both water pathways and changes in water quality in a catchment. LOCAR has increased our understanding of these influences, offering opportunities to manage water resources better. Water managers need this information so that they can predict the movement of pollutants in the groundwater and can decide how much water to extract.

The concept of a stream catchment is entering the ground today might take apparently straightforward – it is the many decades before actually area of land whose water drains into emerging in a stream. the stream. From any given point on a stream, the divide between the land LOCAR has recognised four that slopes towards the stream and important types of that sloping away from it can be easily groundwater movement: picked out on a map. But for chalk G shallow but fast flow streams, which depend upon within a few tens of metres groundwater flow, things aren’t so of the water table; simple. LOCAR discovered that in G deeper slower flow which the River Pang catchment, much of transmits water to a main the underground water moves directly river like the Thames; to the adjacent River Thames and not G very rapid flow where water to the Pang. runs through major cracks The water quality in chalk-fed which channel rainfall directly to streams and rivers depends in part on springs that in dry weather where the water comes from. If it provide the major part of the flow runs rapidly through cracks in the of the surface stream (such as the rock straight into streams it will carry Blue Pool spring which sustains chemicals and sediments from the the Pang in dry summers); LOCAR research has reinterpreted the groundwater surrounding fields. If it takes the G river valley flow where the water catchment and groundwater flows around the Pang, slower path percolating through pores moves through the sands and showing that much of the rain falling onto the in the rock, the impact of the gravels beneath the valley floor catchment flows directly to the Thames. This is chemicals will be delayed so water and stream channel (under dry helping to improve the computer models used in quality will be better (but some of the valley tributaries, for example). forecasting available groundwater. pollutants will emerge into rivers much later). Shallow flow generally contains water Tracers (harmless, inert chemicals that fell as rain in the last few days or used to label a small volume of water) weeks whereas the deeper system may were used by LOCAR scientists to contain much older water that takes partially fill the floor. These gravels show how fast the water moves ten years or more to work its way formed during cold periods in the last through the rocks. In some cases, through the rocks to the stream. two million years when ice covered when tracers were injected in places These waters tend to mix in the valley areas further north in Britain. Today where streams disappear into the bottoms where the rapidly flowing they are an area of concentrated, ground, they reappeared in springs a young water feeds the larger springs relatively rapid groundwater flow, day or two later. In other places the and upwellings and the older water influencing where water reaches the water did not emerge at all. emerges at the base of valley sides and flowing rivers and also acting as a High up in the Pang catchment on in seepages along the channel. store of water beneath the rivers. It is the chalk downs, any new water In the valleys, surface streams helpful to think of the river not sinking into the ground pushes down often disappear into porous rock, but merely as the channel we can see, but the water that entered the catchment LOCAR work confirmed that as a large part of the valley floor earlier. This ‘piston flow’ process beneath these dry valleys water is underlain by gravels and sands all means that a given litre of water often moving through the gravels that carrying water downstream.

The Lowland Catchment Research programme (LOCAR) 9 The nutrient time bomb

In permeable chalk catchments, water moves from the ground surface to the water table in the aquifer mostly through pores in the rock, so agricultural chemicals can take decades to travel from the surface to a river.

As rainwater moves through the soil it becomes contaminated with The trouble with agricultural chemicals, and this phosphorus polluted water eventually works its way into rivers and the water supply. Predicting the rate of water Phosphorous compounds are a movement through aquifers is thus problem for river water quality and important for estimating both water ecology because too much of these nutrients causes excessive growth of quantity and quality. river plants. As plants die and In the chalk downs of southern decay, oxygen levels drop, which England the water table may typically can kill fish in extreme cases. be up to 70 metres below the surface. Phosphorous compounds enter Sampling sediment for phosphorus Some of the rain falling on the surface rivers from agricultural runoff and in the River Pang. diffuses through the pores of sewage effluent. At times of unsaturated chalk slowly, taking many greatest ecological sensitivity (usually dry periods in spring and summer, years to reach the water table. On the when river flows are low), the major source of phosphorus entering rivers is other hand, rain which flows through sewage effluent. LOCAR research has shown that phosphorus is taken up cracks in the rock may reach the by river sediments and that this is an important ‘self-cleansing’ mechanism groundwater almost immediately. for reducing river water phosphorous concentrations downstream of LOCAR scientists have found sewage effluent discharges. When water companies reduce phosphorus in that up to 30 per cent of the water sewage effluent, phosphorus stored in the river bed sediments can be re- takes the rapid route through cracks, released into the river water, but, over time, the levels diminish and the river C h r i s with the rest diffusing slowly through water quality gradually improves. t o p h e

r the chalk.

P i l l i t z / A l a m y As the use of agricultural The main problem for water chemicals has increased over the last quality and ecosystem health is with 50 years, the amount of plant nutrients such as nitrates and chemicals in the chalk has phosphates. In many areas, fertiliser built up, creating a time applications have led to nitrate levels bomb of pollution waiting in rivers and groundwater that already to find its way into the exceed drinking water limits for part rivers which supply our of the time. LOCAR research suggests drinking water. These that if existing agricultural findings have been applications continue, groundwater incorporated into a nitrate will continue to increase for model which predicts the next 70-80 years, and by 2020 when this pollution some rivers will routinely exceed will reach the rivers. drinking water limits. Even if tight The model will help restrictions are put in place now, it catchment managers to will take several decades for nitrate draw up a timetable for concentrations to reduce. taking remedial action.

Not all the chemicals applied in agriculture are used by the crops, much is washed from the soil into the groundwater. LOCAR models can now predict when polluted waters will enter our water supplies.

10 The Lowland Catchment Research programme (LOCAR) Connections between rivers and groundwater

The Water Framework Directive requires that all bodies of water shall be of ‘good status’ by 2015. To achieve this we must fully understand how rivers and aquifers function and, more specifically, how changes to one of them affect the other.

The ecological health of a river and the five rivers in the three LOCAR between aquifer and river is extremely adjoining areas depends on the regular catchments. Broader scale studies have variable within a catchment and can supply of appropriate amounts of involved examining some 350km of also change over time. For example, water and nutrients under specific river, with highly detailed under low river flows fine sediments conditions (such as temperature and investigations over 45km of channel. may be deposited on the river bed oxygen levels). Interfering with these Isotopes (the heavy and light which can lead to a kind of hydraulic conditions – by abstracting water variants of a given element) of sealing of the river. Then, during (from wells or from the river), naturally occurring chemical elements periods of higher flow this ‘lining’ of changing the quality of water entering have been shown to be particularly the river may be stripped away, the river or changing recharge to the useful in understanding these allowing connection again with the groundwater – can have devastating environments – water that has aquifer. impacts on the ecology in and along travelled through different geologies or These findings are important for the river. has been in the ground for different managing the quality of the river. If The headwaters of rivers in lengths of time emerges into the river pollutants are to be eliminated we permeable catchments are particularly with a particular isotope ‘fingerprint’. need to know where they come from vulnerable to exploitation of water Scientists then have a measure of how and where and how they enter the resources because they have a high, water, which initially fell on the river. LOCAR’s work provides the natural variability in their flow. This catchment as rain, enters the river days understanding and detailed theories variability is caused by seasonal or years later. Other tracers – that help managers to know what to fluctuations in groundwater levels. deliberately injected or, like CFCs and look for and where they might find it. The use of water resources in these radon, already present – were also It has also produced knowledge that vulnerable areas must therefore be used to trace routes and age water. will form the basis of new models carefully managed to reduce the These data provide new evidence required for estimating the impact of potential risk of both summer drought of how dry valleys can act as changing climate, land-management and winter flooding. subterranean pathways allowing water practice and water use on the LOCAR scientists have been to move into and out of the river. ecological environment in and close looking at the similarities and Some stretches of a river may lose to the river. differences in the way aquifers and water to the groundwater, while in rivers interact in different catchments. other places the groundwater may This has allowed them to work out re-emerge to add water to the river. what is influencing the delivery of LOCAR discovered that this water to a river and how that water natural exchange (and the associated chemicals) continues its journey to the river mouth. Relevant factors might include where the groundwater comes from locally, the type of rocks, the soils, the form and use of the land, and the plants, animals, insects and micro- organisms present. About 75 LOCAR researchers have been involved in intensive fieldwork programmes for over three The floodplain, the river channel and the riverbed comprise a complex integrated system years to analyse changes in river flow connected by flowing water. Water, fine particles and dissolved chemicals move through the and water quality along the lengths of river itself and in the sediments and rocks beneath it. Source: British Geological Survey.

The Lowland Catchment Research programme (LOCAR) 11 Making space for water, plants and fish

Building development and flood protection works are increasingly disconnecting rivers from their banks and floodplains. However, with sympathetic management, river channels and their margins can form important ribbons of biodiversity across our lowland landscapes. In such systems, water, sediment and plants interact to provide complex, ever-changing habitats for animal life, including fish. LOCAR scientists have been assessing the role of river margins, plants and side channels in maintaining a healthy river ecology.

Rivers continually change as they This large female pike was erode and deposit sediment, and plants caught in the tidal section play a crucial role in engineering their of the River Frome. It ever-changing form. River bank trees was returned to the river after being measured, such as willow and alder, water edge weighed and plants such as reedmace, and photographed. submerged plants such as water crowfoot are all common along lowland rivers. When inundated, these These processes plants slow the current causing sand, are important in both silt and organic material to settle out the main river and in of the water. Sediment accumulations side channels such as create new landforms, new seed banks, natural tributaries, mill a seed bed for the growth of new streams or drainage ditches. plants and sites for decomposition. Contrasts in local habitat Winter floods are vital for dispersing conditions along and between H e

seeds from aquatic and riverside plants. side channels are crucial in a t h e r

Twice as many species are deposited maintaining fish populations and A n g e

across river banks by winter floods l their diversity. Using electronic tags, / N a t than during the low flows of summer. LOCAR researchers found that u r a l

Trees and other rigid plants on the V movements between the main river i s i o n

river margins help to drive progressive and side channels are an important s changes in rivers by trapping and part of life for many river fish. Mill reinforcing sediment. Working in the streams and small tributaries provide Rivers Frome and Tern LOCAR important spawning sites for dace, scientists found that flexible water while the slow-flowing drainage plants, such as water crowfoot, cause ditches are preferred by pike. In the Water crowfoot. annual cycles of sediment trapping as high flows of winter, many types of they grow in the spring and decay in fish use side channels as refuges from for riverbank plant communities and the winter. Water crowfoot also the main channel. to maintain a balance between plant provides habitat for the larvae of filter- These results are important for growth and channel choking where feeding insects and a settling area for river managers. The diversity of river supplies of fine sediment and their waste. As a result, sediment land-forms, flow velocities, patches of nutrients are high. Moreover, it is not accumulations around these plants are sediment and plant communities just the main channel which needs hotspots for processing organic matter. along lowland rivers and streams is sensitive management. Careful During summer, aquatic plants are also heavily dependent upon engineering vegetation removal and desilting at very important for raising river levels, by plants. Sensitive vegetation the mouths of side channels can make shading cool patches of slow-flowing management is critical for habitat them more accessible to fish and their water and inducing faster currents complexity, biodiversity and organic food sources; but highly engineered, between plants which clean river bed matter processing within lowland heavily dredged ditches and other side gravels. rivers. Managers need to give space channels are of very low value to fish.

12 The Lowland Catchment Research programme (LOCAR) How do we judge the health of rivers?

It is no longer sufficient to maintain rivers free from pollution. River managers are now trying to maintain their rivers in an ecological state that is as close to pristine as possible.

Rivers reflect the environments that support dense stands of plants which and in the rising groundwater below, they drain. They are sensitive to all trap silt and support abundant insect nitrate is abundant. But in the thin human activities in their catchments, life, particularly the larvae of simuliid active layer nitrate is chemically to introductions of new plant and blackflies, whose wastes contribute to reduced, with the oxygen atoms being animal species, and to the impacts of the chemical exchanges in the bed. replaced by hydrogen. The climate change. For a long time the The patches differ in the way they ammonium which is produced is quality of rivers has been assessed by allow water to penetrate into the bed actively taken up by growing aquatic measuring a few chemical factors or or, at low flows, to emerge from the plants, and gases such as nitrous oxide by counting the numbers of key types bed into the stream. These contrasts and methane are generated by of fish, invertebrates or plants in the affect the mixing of surface water and microbes. rivers. Assessed on such criteria, the groundwater, the time that water is Such processes also occur in the LOCAR rivers would seem to be of held between the grains of material in River Frome, where it has also been good quality. However, LOCAR the bed, and the rate of chemical shown that methane finds its way scientists have identified significant exchanges. from the poorly oxygenated sediments changes taking place in stream beds In the River Lambourn, LOCAR below plant beds to the atmosphere which suggest that these rivers may be research found that most of the via the stems of the plants. Evidence less healthy than previously thought. important chemical and biological from the conventional biological Stream beds are highly variable. interactions between surface and assessment of these rivers suggests The bed is a mosaic of patches: some groundwater take place in a thin layer they are of good quality, but it seems muddy, some sandy and some rich in organic matter, just 10 to unlikely that the production of gravelly. Some 20cm thick, at the top of the river nitrous oxide and methane is really patches bed sediments. In the characteristic of ‘good ecological flowing water status’. Farming practices leave these column above rivers rich in sediments and nutrients, this layer, creating the conditions in which such gases are produced and leading to low birth and survival rates among fish species of importance to anglers, including salmon and trout.

The Lowland Catchment Research programme (LOCAR) 13 Seeing the big picture

Computer models are being used to combine the results from all the diverse LOCAR studies. These models map how water moves across and through a catchment.

Models of catchments are an important way of bringing together all the information about a river system to help to inform management decisions, develop policies and draw up new regulations. Researchers create sets of equations, solved by computer, which represent the timing and routing of water and its contaminants, and the chemical and biological changes taking place as the water moves through the catchment. These models can predict how change in one part of the catchment will affect the quality and quantity of water in another: for example, how reducing fertiliser applications or increasing groundwater abstractions may affect the wetland habitat around a river. LOCAR data have also shown some limitations of conventional groundwater models. How Contours showing the variation groundwater interacts with the rivers of annual evaporation from is more complicated than was the Pang and Lambourn previously thought. Better models are catchments. needed for managing water to protect river habitats, which often include rare and protected species. LOCAR researchers have produced a new model to show how water and pollutants move through the deep unsaturated zone – the layer between the surface and the water table. The model successfully predicts the movement of pollutants from the soil to the river. The effects of future climate change and agricultural how much rain reaches the fertiliser application can now be groundwater. Other predicted. computer models A promising model of evaporation produced by LOCAR across an entire catchment has been include models of developed. This model incorporates slope erosion, bank the effects of different types of land erosion, movement cover by combining field results with of fine sediments satellite measurements. This work (and hence their gives a useful insight into the water associated chemicals), use of common agricultural crops and and movement of will improve our ability to estimate nitrogen and phosphorus.

14 The Lowland Catchment Research programme (LOCAR) Students’ work This section highlights the work of four of the students who took part in LOCAR.

Helen Moggridge, a PhD student at King’s College London, is studying the regeneration of willow trees on the banks of the River Frome.

Helen found that the survival of willows depends on spring flooding – information which will help river restoration projects. ‘Working in a LOCAR catchment has really helped my research as there is so much data available on the river,’ said Helen. ‘There are also many other LOCAR researchers working on the Frome who have all been really supportive – and it’s much more fun working in a team! The annual meetings have provided an opportunity to publicise my research and meet other scientists in the field. Being part of LOCAR has been a very positive experience, principally because it has given me the opportunity to join a large, diverse research community.’

Nathan Callaghan is studying the water use of woodland growing on saturated soils.

‘I have been measuring the amount of water used by wetland trees growing on sites with different species composition, structure and hydrology,’ Nathan explained. ‘I’ve learnt to use a number of techniques, working at the leaf, tree and landscape scale. The work is a collaboration between CEH and the Open University, but LOCAR provides a much larger framework of research which Nathan Callaghan measuring the amount of has made me realise the relevance of my work and how it fits into the bigger suction a tree leaf is using to draw water up picture.’ from the soil.

Ben Thomas, a student at Exeter University, has been using computer simulation to assess climate change impacts on catchment hydrology and soil erosion.

Ben said, ‘The dynamics of river flow and eroded soil have major implications for the sustainability of river and riparian ecosystems, and my computational contribution to the broader environmental issue is immensely satisfying. My participation in the LOCAR project has given me a solid grounding in conceptualising problems and writing computer programs to solve them. Together with an advanced knowledge of managing and analysing vast quantities of data, my research has afforded me a skill base that is more diverse and transferable than one traditionally associates with PhD study.’

David Hussey is a PhD student at the University of East Anglia studying what happens to pharmaceutical drugs administered to animals.

David said, ‘Antibiotics are widely used in veterinary medicine and large amounts find their way into the soil. But how long do they remain in the soil before being degraded and will they reach the rivers? Are they a danger to humans and are new regulations needed? My research is concerned with an antibiotic used in pig farming in the Pang catchment and seeks to assess the quantities of it in soil and surface waters to inform answers to these questions. LOCAR has given me the opportunity to research an important environmental problem and to make a real contribution.’

The Lowland Catchment Research programme (LOCAR) 15 LOCAR, the Lowland Catchment Research programme, is a £10 million research programme which ran from 2000 to 2006, funded by NERC with additional funding from Defra, the Environment Agency and the Joint Infrastructure Fund. It involves researchers from 14 institutions in 12 major interdisciplinary projects to study and model the hydrology, geology and ecology in three river catchments on porous rock (chalk and sandstone). It aims to provide the science required to support current and future management needs for permeable lowland catchments through an integrated and multidisciplinary experimental and modelling programme. The programme provided a £5m infrastructure for research: £2m for the basic data-collection systems, the management of the data and coordination of the project, and £3m for 12 research grants and 3 research studentships. Another 16 research students joined the programme using funds from other sources.