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Chalk stream

Chalk stream

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Chalk streams have characteristics which set them apart from watercourse
A watercourse is any flowing body of water. These include rivers, streams, anabranches, and so forth.-See also:* physical geography* Environmental flow* Waterway* Hydrology* Wadi-External links:...

s associated with other rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...


Aside from those with an interest in the geological
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 and ecological
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

 disciplines, the term chalk stream is most widely used among a small group of fly fishermen (who fish for trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

 on these rivers utilizing a specific type of artificial fly and their attendant techniques), as the ecology of the chalk streams creates an especially entertaining variation on the general theme of fly fishing
Fly fishing
Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...


Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

 geology is porous, and rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

 falling onto chalk hill
A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit A hill is a landform that extends above the surrounding terrain. Hills...

s percolate directly into the ground, where the chalk acts as an aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

. The water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 filters through the chalk, re-emerging lower down the slope in springs
Spring (hydrosphere)
A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...

. The chalk acts as a temporary reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 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
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 of the emerging surface water is fairly stable and rarely deviates from 10°C (50°F). On cold winter mornings, it can look as though steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 is rising above the relatively warm river.

Chalk is a soluble geology in rainwater because rain is naturally slightly acidic. The products of chalk weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

 are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended
Suspension (chemistry)
In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...

 material (unlike most rivers), but are uniquely mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

-rich. The surface water of chalk streams is commonly described as 'gin clear'. The channel bed consists of angular flint gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

 derived from the natural flint
Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...

 deposits found embedded within the chalk geology that is characteristically free from fine sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....


The unique characteristics of chalk stream ecology are due to stable temperature and flow regimes combined with highly transparent of water and lack of sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

 grade sediment particles.

The chalk streams have been intensively managed for many generations. In the twentieth and twenty-first centuries, much of that management has been aimed at producing the best conditions for fly fishing, and most specifically, dry fly fishing
Fly fishing
Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...

. The chalk streams hold a good number of wild salmonid fish species such as the brown trout
Brown trout
The brown trout and the sea trout are fish of the same species....

 (Salmo trutta), Atlantic salmon
Atlantic salmon
The Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....

 (Salmo salar) and grayling
Grayling (species)
The grayling is a species of freshwater fish in the salmon family of order Salmoniformes. It is the type species of its genus. Native to the Palearctic ecozone, the grayling is widespread throughout northern Europe, from the United Kingdom and France to the Ural Mountains in Russia...

 (Thymallus thymallus). In addition to these there are also considerable numbers of stocked brown trout and stocked rainbow trout
Rainbow trout
The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....

 (Oncorhynchus mykiss). The rich invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 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
Watercresses are fast-growing, aquatic or semi-aquatic, perennial plants native from Europe to central Asia, and one of the oldest known leaf vegetables consumed by human beings...

 production, due to the constant temperature and clean, alkaline, mineral-rich spring water. The Mid Hants Watercress Railway in Hampshire
Hampshire is a county on the southern coast of England in the United Kingdom. The county town of Hampshire is Winchester, a historic cathedral city that was once the capital of England. Hampshire is notable for housing the original birthplaces of the Royal Navy, British Army, and Royal Air Force...

 is so named on account of its use for transporting watercress to London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 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
Abstraction is a process by which higher concepts are derived from the usage and classification of literal concepts, first principles, or other methods....

 by local and national water utility companies.

Chalk stream is a term generally applied to all watercourses originating from chalk hills, including winterbournes
Winterbourne (stream)
A winterbourne is a stream or river that is dry through the summer months. A winterbourne is sometimes simply called a bourne, from the Anglo-Saxon for a stream flowing from a spring, although this term can also be used for all-year water courses....

, stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

s and river
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s. The term chalk stream is used even for larger rivers, which would normally be too large for the term stream.

See Somme River
Somme River
The Somme is a river in Picardy, northern France. The name Somme comes from a Celtic word meaning tranquility. The department Somme was named after this river....

 for a hydrological view of a chalk stream on a larger scale.

Chalk streams of the Southern England Chalk Formation
Southern England Chalk Formation
The Chalk Formation of Southern England is a system of chalk downland in the south of England. The formation is perhaps best known for Salisbury Plain, the location of Stonehenge, the Isle of Wight and the twin ridgeways of the North Downs and South Downs....

 in Berkshire
Berkshire is a historic county in the South of England. It is also often referred to as the Royal County of Berkshire because of the presence of the royal residence of Windsor Castle in the county; this usage, which dates to the 19th century at least, was recognised by the Queen in 1957, and...

, Hampshire, Wiltshire
Wiltshire is a ceremonial county in South West England. It is landlocked and borders the counties of Dorset, Somerset, Hampshire, Gloucestershire, Oxfordshire and Berkshire. It contains the unitary authority of Swindon and covers...

, and Dorset
Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...

  • River Avon
    River Avon, Hampshire
    The River Avon is a river in the south of England. The river rises in the county of Wiltshire and flows through the city of Salisbury and the county of Hampshire before reaching the English Channel through Christchurch Harbour in the county of Dorset....

     and its tributaries including the
    • River Bourne
      River Bourne, Wiltshire
      The River Bourne is a river in the English county of Wiltshire, and a tributary of the River Avon.The Bourne's source is at the eastern end of the Vale of Pewsey, near the village of Burbage. The river cuts through the chalk escarpment at Collingbourne Kingston, to flow south across Salisbury Plain...

    • River Ebble
      River Ebble
      The River Ebble is one the five rivers of the English city of Salisbury.Rising at Alvediston 12 miles to the west it joins the River Avon 2 miles south of Salisbury at Bodenham , after flowing through Ebbesbourne Wake, Fifield Bavant, Little London, Knapp, Mount Sorrel, Broad Chalke, Stoke...

    • River Nadder
      River Nadder
      The River Nadder is one of the chalk stream rivers of southern England, much sought after by fly fishermen because of its clear waters and abundance of brown trout. It is one of the main tributaries of the River Avon, rising from a number of springs and small streams at Donhead St. Mary in south...

    • River Wylye
      River Wylye
      The River Wylye is a classic southern England chalk stream; champagne clear water flowing over gravel. Consequently, it is popular with anglers keen on fly fishing.- Course :...

  • River Frome
    River Frome, Dorset
    The River Frome is a river in Dorset in the south of England. At 30 miles long it is the major chalkstream in southwest England. It is navigable upstream from Poole Harbour as far as the town of Wareham.-Geography:...

  • River Itchen
    River Itchen, Hampshire
    The River Itchen is a river in Hampshire, England. It flows from mid-Hampshire to join with Southampton Water below the Itchen Bridge in the city of Southampton. The river has a total length of , and is noted as one of England's - if not one of the World's - premier chalk streams for fly fishing,...

     and its small tributaries
  • River Kennet
    River Kennet
    The Kennet is a river in the south of England, and a tributary of the River Thames. The lower reaches of the river are navigable to river craft and are known as the Kennet Navigation, which, together with the Avon Navigation, the Kennet and Avon Canal and the Thames, links the cities of Bristol...

  • River Lambourn
    River Lambourn
    The River Lambourn is a chalk stream in the English county of Berkshire. It rises in the Berkshire Downs near its namesake village of Lambourn and is a tributary of the River Kennet, which is itself a tributary of the River Thames.-Perennial River:...

  • Letcombe Brook
    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 at Letcombe Bassett and flows through Letcombe Regis, Wantage, Grove and East Hanney to join Childrey Brook, which is a tributary of the River Ock, which is a tributary of the...

  • River Meon
    River Meon
    The River Meon is a river that flows through an area of Hampshire in southern England known as the Meon Valley, it flows generally southwards from the South Downs to the Solent. For most of its route it is a chalk stream, with a length of 21 miles .The River Meon rises approximately...

  • River Piddle
    River Piddle
    The River Piddle or Trent or North River is a small rural Dorset river which rises next to Alton Pancras church and flows south and then south-easterly more or less parallel with its bigger neighbour, the River Frome, to Wareham, where they both enter Poole Harbour via...

  • River Test
    River Test
    The River Test is a river in Hampshire, England. The river has a total length of 40 miles and it flows through downland from its source near Ashe, 10 km to the west of Basingstoke , to the sea at the head of Southampton Water...

     and its tributaries

Chalk streams of the Southern England Chalk Formation in the Chiltern Hills
Chiltern Hills
The Chiltern Hills form a chalk escarpment in South East England. They are known locally as "the Chilterns". A large portion of the hills was designated officially as an Area of Outstanding Natural Beauty in 1965.-Location:...

 (tributaries of the River Thames
River Thames
The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

 and River Colne
River Colne, Hertfordshire
The Colne is a river in England which is a tributary of the River Thames. It flows mainly through Hertfordshire and forms the boundary between the South Bucks district of Buckinghamshire and the London Borough of Hillingdon...

  • Barton Springs
    Barton-le-Clay is a large village and a civil parish located in Bedfordshire, England. The village has existed since at least 1066 and is mentioned in the Domesday Book...

  • River Bulbourne
    River Bulbourne
    The River Bulbourne is a river in Hertfordshire, England. It runs from Dudswell in Northchurch, through Berkhamsted , Bourne End and Boxmoor to where it joins the River Gade at Two Waters in Apsley near Hemel Hempstead. The total length of the river is 11 Km....

  • River Chess
    River Chess
    The River Chess is a chalk stream which springs from Chesham, Buckinghamshire and runs through Buckinghamshire and Hertfordshire, in south-eastern England. The Chess, along with the Colne and Gade, gives rise to the name of the district of Three Rivers, in which it forms its confluence with the...

  • River Gade
    River Gade
    The River Gade is a river running almost entirely though Hertfordshire. It rises from a spring in the chalk of the Chiltern Hills at Dagnall, Buckinghamshire and flows through Hemel Hempstead, Kings Langley and Croxley Green to Rickmansworth where it joins the The River Colne...

  • Hambleden Brook
  • Hughenden Stream
  • River Misbourne
    River Misbourne
    The River Misbourne rises in a field on the outskirts of Great Missenden, Buckinghamshire, and flows down the Misbourne valley to join the River Colne just north of where the latter is crossed by the A40 Western Avenue....

  • River Pang
    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 the village of Pangbourne.The river, and its water voles, are...

  • River Ver
    River Ver
    The Ver is a river in Hertfordshire, England. The river begins in the grounds of Markyate Cell, and flows south for 12 miles alongside Watling Street through Flamstead, Redbourn, St Albans and Park Street, and joins the River Colne at Bricket Wood....

Chalk streams of the Yorkshire Wolds
Yorkshire Wolds
The Yorkshire Wolds are low hills in the counties of East Riding of Yorkshire and North Yorkshire in northeastern England. The name also applies to the district in which the hills lie....

  • Driffield Beck
    Driffield Beck
    Driffield Beck, East Riding of Yorkshire, England, is one of the premier chalk stream fly fishing rivers in the United Kingdom. The river is often referred to as the Driffield West Beck, and is a river fed by many small chalk streams in the area.-Location:...

    , which is a tributary of the River Hull
    River Hull
    The River Hull is a navigable river in the East Riding of Yorkshire in the north of England. It rises from a series of springs to the west of Driffield, and enters the Humber estuary at Kingston upon Hull. Following a period when the Archbishops of York charged tolls for its use, it became a free...

  • Settrington Beck, which is a tributary of the River Derwent
    River Derwent, Yorkshire
    The Derwent is a river in Yorkshire in the north of England. It is used for water abstraction, leisure and sporting activities and effluent disposal as well as being of significant importance as the site of several nature reserves...

Chalk streams of the Lincolnshire Wolds
Lincolnshire Wolds
The Lincolnshire Wolds is a range of hills in the county of Lincolnshire, England. It is a designated Area of Outstanding Natural Beauty , and the highest area of land in eastern England between Yorkshire and Kent...

  • There are several small chalk streams in the Lincolnshire Wolds including Waithe Beck and the River Bain
    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, a village on The Viking Way long-distance footpath, and flows through or past the villages of Burgh on Bain, Biscathorpe, Donington on Bain, Goulceby with...


Chalk streams of Kent:
  • Nailbourne
    Little Stour
    The Little Stour is one of the tributaries of the River Stour in the English county of Kent. The upper reaches of the river are better known as the Nailbourne, whilst the lower reaches were once known as the Seaton Navigation....