Britain’s natural springs, ponds and lakes are distributed very unevenly. The North and West are plentifully endowed with a great variety of natural still water bodies while the South and East are impoverished. This is because of basic geological differences separating Scotland, the Pennines, the Lake District and the South Western and Welsh uplands from the rest of the country. The geologically old and complex rocks of the North and West are hard and impervious, yielding poor, thin soil and plentiful runoff accentuated by high rainfall. The South and East are clothed in relatively young, unconsolidated and permeable materials which absorb and store a higher proportion of the more modest rainfall. Those small natural ponds which do occur in the South and East are found on clay, or on the impervious pans which form locally where iron leaches from the upper soil layers. In the Midlands, ponds fill hollows in the great blanket of glacial till which overlays the region’s bedrock, but elsewhere the till is generally too porous to hold much water without man’s help.
Springs are fed purely from ground water supplies. Ground water may flow along an impermeable layer to emerge where it is cut by a hillside, or may be forced up by the water pressure in surrounding permeable strata to form natural artesian wells. Some springs are isolated, but most overflow to feed stream channels while others occur at the bottoms of larger pools and lakes. Some are short-lived, as in Snowdonia and the Highlands where many bubble up for a few days after heavy rain but are otherwise inactive. Permanent springs are uniquely stable since their water supply is assured at a constant or seasonally cyclical rate irrespective of day-to-day rainfall and variations in runoff which affect other water bodies. Springs often support a limited but distinctive fauna and flora adapted to the cool, well-oxygenated and often mineral-enriched water.
Natural ponds and lakes are of many types. In northern Scotland, where the old mountain blocks have been severely split by faults, the glaciers which gouged out valleys along these lines of weakness left lakes which are typically long, narrow, deep and steep-sided. Britain’s deepest at 328m (1,007’) is Loch Morar. Loch Ness, also a fault lake, has a greater mean depth at 132m (433’) and is over 33km (21 miles) long while averaging less than 1.6km (1 mile) in width.
Glacial ponds and lakes take a number of other forms. Old river valleys, deepened and reshaped by flowing ice, contain lakes which conform to the scoured basin. Usually this is relatively long and deep, as is the case with many Scottish lochs and with Lake Windermere in the Lake District.
Where glacial ice spread over a wide plain its power was dissipated and it deposited at its foot tons of boulders, grit and clay brought down from above. These moraines remained after the melt, backing up fairly shallow bodies such as Loch Leven, which is 5.8km (3.6 miles) long by 4.3km (2.7 miles) wide with a mean depth of only 4.6m (15’).
‘Cwms’ (Welsh) or ‘corries’ (Gaelic) formed high on mountains where ice repeatedly built up and broke off, pulling the rock face with it. The glacier at the cliff foot often scoured out a basin behind a lip of hard rocks which afterwards retained a nearly circular lochan tarn or lake. Good examples are found at Cwm Idwal and Snowdon.
Glaciers sometimes broke into separate blocks around which deposits heaped to form steep-sided rings. When a block melted it often burst through one wall and drained the ‘kettle hole’, but elsewhere no outlet formed and ponds remained. Some of the Staffordshire and Cheshire meres are thought to be kettle hole ponds.
Some Cheshire meres, unlike typical kettle hole ponds, lie in shallow depressions with gently sloping banks. These were probably caused by the collapse of underlying salt domes due to their penetration by ground water. Subsidence lakes are rather rare. Foremost in Britain is Lough Neagh in Northern Ireland, which fills a sunken section of the vast plateau of basaltic lava which covers most of County Antrim. With a surface area of 396 km2 (153 square miles), this is Britain’s largest water body, but it is also very shallow at only 17m (56’) maximum depth.
Lakes and pools often occur along unstable coastlines. Wherever cliffs have a tendency to subside or slip, short- lived pools may be impounded on the beach below. Where shingle bars close the mouth of a drowned river valley, fresh water is retained, as at Covehithe and other Suffolk coastal broads and at Slapton Ley, Devon. Where longshore drift is strong and coastal waters shallow, river mouths may be deflected and cut off to form lagoons which may in time change from brackish to fresh. A famous example is the Little Sea on South Haven Peninsula, Dorset, which developed between the 17th and 19th Centuries. The Somerset Levels are thought to have begun in the same way and to have been for a time a shallow lake before silting up and becoming boggy.
Flowing waterways almost always have associated pools in backwaters where debris temporarily dams the current. Meandering watercourses may become cut off to form short-lived oxbow lakes to the side of the main channel. Wetlands also have associated pools, occurring wherever the land dips below the water table. Some of the largest are found on the flat-topped Pennines in Yorkshire, where the natural erosion or ‘hagging’ of the raised dome of peat creates temporary wind and rain-scoured hollows in the bog surface. The pools gradually coalesce and eventually drain away through a channel or ‘grough’ cut through the rim of peat.
Waterways of any type are rare on carboniferous limestone. Malham Tarn in North Yorkshire is particularly notable. Although it occurs in the middle of the limestone belt it actually rests on an impervious layer of shale. Because of its location it supports, with its associated fens and bogs, a unique flora combining upland and lowland, acid and calcareous features.
Most of the estimated 338,000 ponds in England and Wales are artificial. Not necessarily intentional, they occur because human activity has altered local topography so that water collects in impermeable hollows in what had been generally porous strata. Although about one quarter are found in the hill farms of the West Country, Wales and the North, most occur in early-enclosed parts of the lowlands: a quarter of the total in Norfolk and Cheshire and the rest scattered through the other lowland counties.
From earliest times tracks were routed to take advantage of natural watering places. Simple springs or damp hollows developed into ponds due as much to trampling by livestock as to active encouragement by men. The Romans may have built ponds to water their horses and drain their roads, but direct evidence is scant. More lasting, in the long run, were the efforts of anonymous farmers who tapped springs, built small dams, puddled permeable bottoms with clay and protected them with chalk or gravel to store water where most convenient.
High on the chalk downs of Sussex, parts of Wiltshire and Berkshire, reliable natural water supplies are very scarce. Here are found small, generally circular ‘dew ponds’ surviving apparently unaided despite long- standing use (until a few decades ago) for watering stock. Ponds of similar design, not always on chalk, occur in small numbers in Dorset, Hertfordshire, Yorkshire and Derbyshire. Dew ponds were once popularly believed to be of miraculous origin (‘dew’ considered a corruption of ‘Dieu’), or to be man-made in Neolithic times, or to be literally topped up as much as necessary by periodic heavy dews. These theories were systematically demolished in 1939 by A J Pugsley, whose Dewponds in Fable and Fact surveys their location, design and history and shows that they are, invariably, rain ponds.
A few dew ponds can be proven to be very old, such as Oxonmere on Pewsey Down which is recorded in the Domesday Book. Most were built sometime between the end of the medieval period and the 19th Century, and as late as the 1930s they were still occasionally constructed by professional pond makers. Many are situated below the lip of a rise or next to a road which acts as a catchment, providing some runoff water, but some on the open tops depend on direct rainfall exclusively. Many have gone dry over the years due to lack of maintenance and, now that piped water has replaced them for farm use, grassed-over hollows may soon be all that remain. Those which seem truly everlasting turn out, on inspection, to be old brickholes. These sometimes occur high on the chalk where clay pockets were quarried for local use. The resultant flooded pits were adapted for livestock. This may have given the first dew pond makers the idea, but from then on techniques developed on their own. Dew pond design is discussed in Chapter 6 – New ponds.
Medieval manors and monasteries depended on ponds for a variety of purposes including watering livestock, storing drinking water, which was often piped from springs, and keeping fish. Fish ponds ranged from simple ‘stew’ ponds to groupings of specialised hatchery ponds, each designed for a different size or type of fish. Fortified farmhouses often had moats as their first defences, which may remain, even where the houses have long vanished, as circular, rectangular or E-shaped ponds. Thousands of moats still exist in northwest Essex, west Suffolk and west Cambridgeshire, often within the hamlet or village which sprung up in the manor ’s shelter.
Some simple manor ponds were later transformed into quite grand estate lakes. During the 18th Century, the heyday of the English School of landscape architecture made famous by Capability Brown, many unpretentious streams were dammed to form sinuous lakes very different in appearance from functional round or oblong fish ponds. Today’s visitors often fail to realise how carefully engineered some of these ‘natural’ lakes are. Some estates turned their ponds into duck decoys by digging ‘pipes’ at the corners which tapered away and finally ended in funnel nets. Whatever the wind, one pipe would be situated so that a specially trained ‘piper ’ dog could lure ducks into it. Most decoys have fallen into decay since the end of market-fowling days, but a few have been restored for ringing and research purposes.
Village ponds often pre-date their villages. Where a crossroads met near a pond two attractions combined to encourage settlement. Elsewhere, existing villages spread out to surround old commons or manor ponds, often locating a market beside them. The ponds eventually were surrounded by shops and houses or confined to small parks and squares.
Before piped supplies, ponds were the usual source of water for fire-fighting. Early engines were simple mechanical bucket brigades and when pumps were introduced they were often fouled by sludge. Ponds swelled wooden cartwheels which had dried and loosened from the hubs on hot summer days and so were often lined with bricks or flat stones to support the wagons as they soaked. Their banks grew willows for making baskets, creels and panniers and for use as thatching ‘spics’ or spars. In Somerset special pools 1-2m (3-6’) deep were dug where cut willow was placed to sprout for making withies. Both the craft and the small, rectangular pools survive today.Another specialised pool was the watercress bed. Today these are often concrete lined and rigorously managed to keep unwanted ‘weeds’ out of the crop, so their wildlife value tends to be limited.
Until the advent of steam-driven machinery towards the end of the 18th Century, virtually all mechanised industrial activity depended on water for motive force. Water-powered corn mills, often on sites used since Norman times, dotted the country until a hundred years ago. Staffordshire and the Weald are characterised by ‘hammer ponds’, so called because the head of water was used to drive tilt-hammers and other glass- and iron-producing machinery. Hammer ponds were often located in wooded areas where charcoal was available for furnaces and forges. Early in the Industrial Revolution, Lancashire and the Yorkshire Pennines sprouted new hamlets, some of which seem quite isolated today, as the cotton and woollen industry grew. Initially every beckside cottager participated in washing and carding. As new machinery was introduced, the focus shifted to the valleys where the larger streams were dammed and mills established.
Quarries of many types tend to flood after abandonment. Clay and marl pits, which furnished material for bricks, daub and fertiliser, left many small, steep-sided ponds scattered over the country. In the South West similar pits in the upland plateau furnished rotten granite which was carried to the valleys to build cob houses. Flooded stone quarries, unfortunately, are often polluted by stone dust, as in the North Wales slate workings. In the South and Midlands, today’s immense brick and gravel operations provide challenging problems of renovation but can, in some cases, form the basis for new recreational or conservation areas. Gravel pits are generally shallower and more easily developed for wildlife conservation than are clay pits. Great Linford in Buckinghamshire, Sevenoaks in Kent and the Lea Valley area, amongst others, demonstrate the success of gravel pit restoration for wildlife.
Wherever peat was used for fuel, the land is dotted with old, shallow diggings. Many of these form pools within larger bogs and fens, greatly diversifying the wetlands habitats. The Norfolk Broads originated in this way. They were dry pits, supplying fuel until the end of the 13th Century when, after being excavated to a depth of 2.4-3m (8-10’), they eventually reached underlying alluvium or clay or flooded, despite pumping, due to the high water table. Once abandoned, their origins were soon forgotten and, until recent painstaking historical research and detailed corings proved otherwise, they were assumed to be natural features.
In coal and salt mining districts, subsidence due to tunnelling may create shallow pools or ‘flashes’. The gentle slopes and shallow water of these pools and wetlands make excellent wildlife habitats, and many are now officially recognised as SSSIs. Their value as semi-natural habitat and educational resource is enhanced by their location in the heart of industrial and urban areas.
Many other industrial processes create waterways and wetlands which can be of considerable value for wildlife. These include storage lagoons for silt and other materials, water storage and treatment systems. With increasingly stringent controls on discharge of effluent into watercourses, industries are investing in effluent and water treatment systems which are cost-effective to operate, and natural systems are proving their worth. Several hundred reedbed systems have been constructed in the UK over the last decade, to purify industrial and domestic effluent. Industries requiring large amounts of water have traditionally located near river, estuary or coastal supplies, and to ensure continuity of supply, some have required the construction of reservoirs.
The history of piped water goes back to Roman times, but it was only during the Industrial Revolution, when traditional supplies became inadequate due to pollution and the increasing urban population, that reservoirs were commissioned to supply pure water from the headstreams of major rivers to large cities. Canal builders also needed impoundments to feed water into the highest points on canals to replenish water lost at the ends. Early 19th Century reservoirs were usually earth banked with puddled clay cores; the first masonry dam was not built until 1892. The flooding of land for reservoirs has always caused controversy, but many have become important wildlife and recreational resources. For wildlife, the most valuable have been formed by the flooding of shallow, lowland valleys, such as Chew Valley Lake and Rutland Water.