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The Science of The Harnham Water Meadows

Sluice under construction by The Trust

Sluice under construction
by The Trust

What is a Water Meadow?

Visitors to Harnham near Salisbury and to the surrounding river valleys are often intrigued but the complexity of channels, hatches, sluices, aqueducts and other water control features on the floodplain of so many of the rivers. Furthermore, the ‘ridge and furrow’ type appearance of the river valley meadows can be puzzling. These features comprise the famous water meadows of the Wessex region.

A water meadow is a man-made pasture irrigation system operated at the discretion of the farmer. The aim is either to increase total grass production, or bring it forward in time during the agricultural year. The operation of water meadows, a practical knowledge of drowning meadows, a practical knowledge of drowning is based upon skilful construction and year-round management. The high degree of management differentiates them from grazingmarshes and from flood meadows and other naturally floodable areas. Irrigation for boosting pasture productivity is recorded from several

European countries. These range from Sweden to Spain and in Switzerland glacial melt-waters have been used to irrigate mountain pastures.

Three basic forms of irrigation systems are distinguished. The first are catchwork (or catchmeadow) systems where water from springs and streams is diverted along contoured gutters cut into a hillside and controlled such that it overflows this high-level watercourse to run downhill through the grass to be collected in a gutter at a lower level. The second type to which belong most of the valley-bottom floodplain water meadows of the Salisbury area, are termed bedworks. Both these kinds of water meadow are known from southern England, Germany and around Milan in modern Italy, their form depending on the topography. Another type occured on flat floodplain areas where water is caused to back-up above a dam and are called floating upward systems. These were not so efficient.

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Why Watermeadows are found in these valleys

Why the chalk provides a good aquifer to supply the water

Layout of Typical Bedwork Watermeadow

Sketch map of the Harnham system

Described by an historian as ‘one of the greatest achievements of English Agriculture’ these (often derelict) bedwork systems are now the centre of enormous interest from many scholars, environmental scientists, archaeologists, engineers and conservationists. In bedwork systems, water is diverted from a river, canal or main carriage to irrigate grass ridges constructed in the alluvial soils. Large hatches control the flow of water into carriers that in turn feed tapered gutters cut into the tops of ridges. A floated ridge (top right) is from where water descends through the grass on either side to drains. While catchworks are know from the upland areas of Britain, from the south-west to Scotland, bedworks are best known from the chalkland valleys of Wiltshire, Hampshire and Dorset where the soil is particularly suitable. Typical soil being a Frome series. This calcareous silty clay loam makes fertile meadow soil (picture bottom right).

Water meadows cause the grass to grow by bringing production earlier in the spring (by as much as one month) through warming the soil above 5oC. These trigger temperate grass growth producing the early bite for grazing animals.

Click here for more information on water temperature and oxygen.

In the past, the ‘Little Ice Age’ would make it more important to warm the grass and protect from frost. Click here for more information.

Click here for the visual effects of watering and the re-growth of grass.

Floating at Sammell’s Acre, Harnham, January 2007

Floating at Sammell’s Acre, Harnham, January 2007

A Frome series soilA Frome series soil

Otherwise, irrigation re-wets the soil to produce a hay crop later in the season while the flowing water used in floating supplies oxygen to the sward during floating and, importantly, the water contains fertilising sediment. Nutrients such as nitrogen and phosphorous my be found associated with sediment or dissolved in the water.

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Click here for more information on the operation of watermeadows.

Click here for a model for their operation.

The practice was known in medieval Europe, but it is in the ‘ Wessex’ region of southern England during the post-medieval period that water meadows reached their zenith. After irrigation events in winter and early spring (that varied from a few days to several weeks) the meadows were drained and animals were turned out on them to graze. Although today it is largely cattle that are seen on the meadows of the Salisbury Avon Valley, historically it was sheep that were central to the rural economy of Wessex.

Regionally there was the sheep-corn system, a truly remarkable integrated agricultural system of soil, water and nutrient management. Water meadows had spread rapidly since the sixteenth century and their success depended upon their production of animal products (notably sheep meat and wool), on producing a reliable hay crop and boosting the productivity of cereal crops grown on the thin chalky soils of the downland located adjacent to the valley bottoms. Animals were turned out on the meadows by day (usually to graze at very high stocking densities) and herded by the shepherd to be ‘folded’ on the cereal land by night. Their dung and urine thereby provided fertiliser for the crop. As time progressed, it was the impact on the cereal land that was economically most significant; the corn representing an important cash crop for the farmer. The sheep-corn system was threatened by the introduction of artificial fertiliser in the nineteenth century, and largely declined in the agricultural recession of 1870s. From that time, where meadow irrigation survived, it was through finding new markets for hay, milk and other cattle products around Salisbury in the nineteenth and twentieth century.

Surviving water meadow systems are a part of the heritage of Wessex. More than a mere historical curiosity there is great interest in them from landowners and farmers, from conservation bodies (such as the Harnham Water Meadows Trust) and local authorities in seeing their preservation and re-instatement. They provide not only living archaeological monuments but are also systems providing important habitats (for example wading birds and the southern damsel fly) and environmental functions including fertilisation and detention of floodwater. Recent research is showing their ability to trap sediment, utilise phosphorus and maybe modify the temperature of river systems in a beneficial way.

Hadrian F. Cook

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Short Bibliography

Cook, H.F., Cutting, R.L., Buhler, W. and Cummings, I.P.F. (2004).
Productivity and soil nutrient relations of bedwork watermeadows in southern England.
Agriculture, Ecosystems and Environment 102(1) 61-79.

Cook, H.F., Stearne, K. and Williamson, T. (2003).
The Origins of water meadows in England. Agricultural History Review 51 (II) 155-162.

Cook, H.F . and Williamson, T. (eds) (1999).
Water Management in the English Landscape: Field, Marsh and Meadow, Edinburgh University Press.
See Chapters by R. Cutting and I. Cummings, S. Wade Martins and T. Williamson and J. Bettey

Cutting R., Cook, H.F. and Cummings, I . (2003).
Hydraulic conditions, oxygenation, temperature and sediment relationships of bedwork watermeadows.
Hydrological Processes 17, 1823-1843.

Cowan M. (2005).
Wiltshire water meadows. Hobnob Press.

Cook H. and Williamson T. (eds) (2006)
Watermeadows: History, ecology and conservation. Windgather Press.

Everard M . (ed) (2005)
Water Meadows: Living treasures in the English Landscape Forrest Press.

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