Chalk streams are rivers that rise from springs in landscapes with

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

bedrock. Since chalk is

permeable Permeability, permeable, and semipermeable may refer to: Chemistry *Semipermeable membrane, a membrane which will allow certain molecules or ions to pass through it by diffusion *Vascular permeability, the movement of fluids and molecules betwe ...

, water percolates easily through the ground to the

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

and chalk streams therefore receive little surface runoff. As a result, the water in the streams contains little organic matter and

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

and is generally very clear. The beds of the rivers are generally composed of clean, compacted gravel and

flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and sta ...

s, which are good spawning areas for

Salmonidae Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefis ...

fish species. Since they are fed primarily by

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteris ...

s, the flow rate, mineral content and temperature range of chalk streams exhibit less seasonal variation than other rivers. They are mildly alkaline and contain high levels of nitrate,

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

and silicate. In addition to algae and diatoms, the streams provide a suitable habitat for

macrophytes Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

(including water crowfoot) and oxygen levels are generally supportive of coarse fish populations. Of the 210 rivers classified as chalk streams globally, 160 are in England.

Geology and hydrology

Chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

is a highly

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

and

rock, and

rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water ...

falling onto chalk topography percolates directly into the ground, where the chalk layer acts as an

. The

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

flows through the chalk bedrock, re-emerging lower down the slope in springs. The chalk acts as a temporary

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

by regulating the amount of water supplied to the springs. This is why many chalk streams in the UK have stable flow regimes that vary only slightly over time. The temperature of the emerging surface water is fairly stable and rarely deviates from . On cold winter mornings, water vapour from the relatively warm stream condenses in the cold air above to form fog. Chalk is slightly soluble in

water because rain is naturally slightly

acidic In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...

. The products of chalk

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...

are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended material (unlike most rivers), but are considered "

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

-rich" due to the dissolved calcium and

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s. The surface water of chalk streams is commonly described as "gin clear". The channel bed consists of angular

gravel derived from the natural flint deposits found embedded within the chalk geology that contains relatively low amounts of clay and silt deposits. The unique characteristics of chalk stream ecology are due to stable temperature and flow regimes combined with highly transparent water and lack of

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class o ...

grade sediment particles.

Ecology

The chalk streams have been intensively managed for many generations. In the 20th and 21st centuries, much of that management has been aimed at producing the best conditions for fly fishing, and most specifically, dry fly fishing. The chalk streams hold a good number of wild salmonid fish species such as the brown trout (''Salmo trutta''), Atlantic salmon (''Salmo salar'') and grayling (''Thymallus thymallus''). In addition to these there are also considerable numbers of stocked brown trout and stocked rainbow trout (''Oncorhynchus mykiss''). The rich

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

life and characteristic transparent shallow water make chalk rivers and streams particularly suited to fly fishing. Many of the chalk stream springs are also used as sites for

watercress Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family Brassicaceae. Watercress is a rapidly growing perennial plant native to Europe and Asia. It is one of the oldest known leaf v ...

production, due to the constant temperature and clean, alkaline, mineral-rich spring water. The Mid Hants Watercress Railway in

Hampshire Hampshire (, ; abbreviated to Hants) is a ceremonial and non-metropolitan county in western South East England on the coast of the English Channel. Home to two major English cities on its south coast, Southampton and Portsmouth, Hampshire ...

is so named on account of its use for transporting watercress to London from local chalk streams. A number of the chalk aquifers and associated groundwater sources related to chalk streams and rivers are used for

water abstraction Water extraction (or water withdrawal) is the process of taking water from any source, either temporarily or permanently, for flood control or to obtain water for, for example, irrigation. The extracted water could also be used as drinking wate ...

by local and national water utility companies.

Chalk streams of England

Although chalk streams are generally watercourses originating from chalk hills, including winterbournes, streams, and rivers, the term ''chalk stream'' is used even for larger rivers, which would normally be considered too large for the term ''stream''. The Somme in northern France is a chalk stream on a larger scale. Chalk streams of the

Southern England Chalk Formation Downland, chalkland, chalk downs or just downs are areas of open chalk hills, such as the North Downs. This term is used to describe the characteristic landscape in southern England where chalk is exposed at the surface. The name "downs" is deriv ...

in Berkshire,

Wiltshire Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of . It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershire ...

Dorset Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset. Covering an area of , ...

and the

Isle of Wight The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...

: * River Avon and its tributaries including the ** River Bourne ** River Ebble **

River Nadder The River Nadder is a tributary of the River Avon, flowing in south Wiltshire, England. Course The river flows north from Ludwell to West End where it is joined by the Ferne Brook, close to the Lower Coombe and Ferne Brook Meadows site of spec ...

River Wylye The River Wylye ( ) is a chalk stream in the south of England, with clear water flowing over gravel. It is popular with anglers for fly fishing. A half-mile stretch of the river and three lakes in Warminster are a local nature reserve. Cour ...

* River Frome * River Itchen and its small tributaries *

River Kennet The Kennet is a tributary of the River Thames in Southern England. Most of the river is straddled by the North Wessex Downs AONB (Area of Outstanding Natural Beauty). The lower reaches have been made navigable as the Kennet Navigation, which � ...

* River Lambourn *River Loddon *

Letcombe Brook Letcombe Brook is a stream in the Vale of White Horse in Oxfordshire, England. It rises at the foot of the Berkshire Downs in Letcombe Bassett and flows through Letcombe Regis, Wantage, Grove and East Hanney to join Childrey Brook, which is ...

River Meon The River Meon () is a chalk stream in Hampshire in the south of England. It rises at East Meon then flows in a generally southerly direction to empty into the Solent at Hill Head near Stubbington.Hampshire County Council (2006). Activities at ...

River Piddle The River Piddle or Trent or North River is a small rural Dorset river which rises in the Dorset Downs and flows into Poole Harbour near Wareham. Etymology The river's name has Germanic origins and has had various spellings over the years. I ...

River Test The River Test is a chalk stream in Hampshire in the south of England. It rises at Ashe near Basingstoke and flows southwards for to Southampton Water. Settlements on the Test include the towns of Stockbridge and Romsey. Below the village of ...

and its tributaries * River Caul Bourne Chalk streams of the Southern England Chalk Formation in the Chiltern Hills, Hertfordshire and Surrey (tributaries of the

River Thames The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after the R ...

, River Lea and River Colne): * River Ash * Barton Springs *

River Beane The River Beane is a short river in the county of Hertfordshire, England. A tributary of the River Lea, it rises to the south-west of Sandon in the hills northeast of Stevenage and joins the Lea at Hartham Common in Hertford. Watermills ...

River Bulbourne The River Bulbourne is a small river in Dacorum, Hertfordshire, England. The word bourne derives from the Anglo-Saxon word for a stream. It is an unnavigable tributary of the River Gade, which flows into the River Colne, which in turn is a ...

River Chess The River Chess is a chalk stream that rises near Chesham in the Chiltern Hills, and flows for through Buckinghamshire and Hertfordshire to its confluence with the River Colne in Rickmansworth. The Chess, along with the Colne and Gade, gi ...

River Gade The River Gade is a river running almost entirely through Hertfordshire. It rises from a spring in the chalk of the Chiltern Hills at Dagnall, Buckinghamshire and flows through Hemel Hempstead, Kings Langley, then along the west side of Watfo ...

* Hambleden Brook *

Hogsmill River The Hogsmill River in Surrey and Greater London, England is a small chalk stream tributary of the River Thames. It rises in Ewell and flows into the Thames at Kingston upon Thames on the lowest non-tidal reach, that above Teddington Lock. The ...

* Hughenden Stream * River Lea *

River Mimram The River Mimram is a river in Hertfordshire, England. Geography The river valley known locally as the Mimram Valley is named after the River Mimram, which rises from a spring to the north-west of Whitwell, in North Hertfordshire, England, a ...

River Misbourne The River Misbourne rises in a field on the outskirts of Great Missenden in Buckinghamshire, passing through Little Missenden, Old Amersham, Chalfont St Giles, Chalfont St Peter and under the Chiltern railway line and the M25 motorway to its ...

River Pang The River Pang is a small chalk stream river in the west of the English county of Berkshire, and a tributary of the River Thames. It runs for approximately from its source near the village of Compton to its confluence with the Thames in th ...

River Quin The River Quin is a small watercourse which rises near Barkway in north east Hertfordshire, England. The river is fed by a number of sources including springs from Biggin Moor, Great Hormead Brook, Little Hormead Brook and various field ditch ...

River Rib The River Rib originates near the East Hertfordshire village of Therfield and runs parallel with the A10 through Chipping, Wyddial, Buntingford, Westmill, Braughing, Puckeridge and Standon, before dividing the villages of Thundridge and ...

River Stort The River Stort is a river in Essex and Hertfordshire, England. It is 24 miles (38 km) long and flows from just south of the village of Langley to the River Lea at Hoddesdon. The river's name is a back-formation; the town of Bishop's Sto ...

River Ver The Ver is a long chalk stream in Hertfordshire, England. It is a tributary of the River Colne. Course The source is in the grounds of Lynch Lodge, Kensworth Lynch on the west side of the A5 trunk road and stays on the west side for som ...

Chalk streams of the

Yorkshire Wolds The Yorkshire Wolds are low hills in the counties of the East Riding of Yorkshire and North Yorkshire in north-eastern England. The name also applies to the district in which the hills lie. On the western edge, the Wolds rise to an escarpment wh ...

: * Driffield Beck, which is a tributary of the River Hull *

Gypsey Race The Gypsey Race is a winterbourne stream that rises to the east of Wharram-le-Street and flows through the villages of Duggleby, Kirby Grindalythe, West Lutton, East Lutton, Helperthorpe, Weaverthorpe, Butterwick, Foxholes, Wold Newton, Bur ...

, the most northerly chalk stream in Europe, runs east to the sea at

Bridlington Bridlington is a coastal town and a civil parish on the Holderness Coast of the North Sea in the East Riding of Yorkshire, England. It is about north of Hull and east of York. The Gypsey Race enters the North Sea at its harbour. The 2011 ...

* Settrington Beck, which is a tributary of the River Derwent Chalk streams of

Lincolnshire Lincolnshire (abbreviated Lincs.) is a Counties of England, county in the East Midlands of England, with a long coastline on the North Sea to the east. It borders Norfolk to the south-east, Cambridgeshire to the south, Rutland to the south-we ...

: There are several chalk streams in the

Lincolnshire Wolds The Lincolnshire Wolds are a range of low hills in the county of Lincolnshire, England which run roughly parallel with the North Sea coast, from the Humber Estuary in the north-west to the edge of the Lincolnshire Fens in the south-east. They ar ...

including *

Great Eau The Great Eau is a river in Lincolnshire, England, rising from the Chalk Streams of the Lincolnshire Wolds The Lincolnshire Wolds are a range of low hills in the county of Lincolnshire, England which run roughly parallel with the North Sea ...

* River Waring *

River Bain The River Bain is a river in Lincolnshire, England, and a tributary of the River Witham. The Bain rises in the Lincolnshire Wolds at Ludford,J. N. Clarke, (1990), ''The Horncastle and Tattershall Canal'', Oakwood Press, a village on The Vik ...

* River Lymn * River Lud, *Laceby Beck, *Nettleton Beck, *Waithe Beck, Chalk streams of Kent: *

River Dour The River Dour is a chalk stream in the county of Kent, England. It flows from the villages of Temple Ewell and River between which is a neighbourhood served by a railway station, Kearsney. It is roughly long. It originally had a wide estu ...

* Nailbourne *

River Darent The Darent is a Kentish tributary of the River Thames and takes the waters of the River Cray as a tributary in the tidal portion of the Darent near Crayford, as illustrated by the adjacent photograph, snapped at high tide. 'Darenth' is frequen ...

*(there are more in Kent than listed here) Chalk streams of Norfolk: *

Babingley Babingley is a village and former civil parish, now in the parish of Sandringham, in the King's Lynn and West Norfolk district, in the county of Norfolk, England, about northwest of Castle Rising and north-north-east of King's Lynn. In 1931 th ...

* Bure *

Burn A burn is an injury to skin, or other tissues, caused by heat, cold, electricity, chemicals, friction, or ultraviolet radiation (like sunburn). Most burns are due to heat from hot liquids (called scalding), solids, or fire. Burns occur ma ...

* Gaywood * Glaven * Heacham * Hun * Ingol * Mun * Nar * Stiffkey *Tas * Waveney *

Wensum The River Wensum is a chalk river in Norfolk, England and a tributary of the River Yare, despite being the larger of the two rivers. The river is a biological Site of Special Scientific Interest and Special Area of Conservation. The Wensum is ...

* Wissey * Yare * Weybourne Beck Chalk streams of Suffolk: * River Lark * River Linnet

References

External links

Wildlife Trusts - chalk streamsWWF - England's Chalk Streams under threat
Includes an index of all chalk streams in England in linked report
FishPal - about chalk streams
Includes a small list of chalk streams and their locations {{Rivers, streams and springs, state=collapsed Water streams

Geology and hydrology

Ecology

Chalk streams of England

See also

References

External links