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.

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