Chalk streams are rivers that rise from springs in landscapes with chalk bedrock . Since chalk is permeable , water percolates easily through the ground to the water table and chalk streams therefore receive little surface runoff . As a result, the water in the streams contains little organic matter and sediment and is generally very clear.
22-878: The Piscatorial Society is one of the oldest angling societies in England, if not the world. It was founded in 1836 and still flourishes today. It leases fly fishing water on a number of chalk streams in Hampshire and Wiltshire , including the Wylye , the Test , the Itchen and the Hampshire Avon . It no longer has a base in London , but maintains a Rod Room on one of its Wiltshire rivers. Although members originally fished for all sorts of fish (the society's crest still represents
44-417: A suspension's shelf life. This time span needs to be measured in order to provide accurate information to the consumer and ensure the best product quality. "Dispersion stability refers to the ability of a dispersion to resist change in its properties over time." Dispersion of solid particles in a liquid. Note : Definition based on that in ref. Multiple light scattering coupled with vertical scanning
66-467: A temporary reservoir 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 10 °C (50 °F). On cold winter mornings, water vapour from the relatively warm stream condenses in the cold air above to form fog. Chalk
88-478: Is dispersed throughout the external phase (fluid) through mechanical agitation , with the use of certain excipients or suspending agents. An example of a suspension would be sand in water. The suspended particles are visible under a microscope and will settle over time if left undisturbed. This distinguishes a suspension from a colloid , in which the colloid particles are smaller and do not settle. Colloids and suspensions are different from solution , in which
110-465: Is often required for the formulator to use further accelerating methods in order to reach reasonable development time for new product design. Thermal methods are the most commonly used and consists in increasing temperature to accelerate destabilisation (below critical temperatures of phase and degradation). Temperature affects not only the viscosity, but also interfacial tension in the case of non-ionic surfactants or more generally interactions forces inside
132-480: Is slightly soluble in rainwater because rain is naturally slightly acidic . The products of chalk weathering are dissolved in rainwater and are transported in stream flow. Chalk streams transport little suspended material (unlike most rivers), but are considered " mineral -rich" due to the dissolved calcium and carbonate ions . The surface water of chalk streams is commonly described as "gin clear". The channel bed consists of angular flint gravel derived from
154-561: Is the most widely used technique to monitor the dispersion state of a product, hence identifying and quantifying destabilization phenomena. It works on concentrated dispersions without dilution. When light is sent through the sample, it is back scattered by the particles. The backscattering intensity is directly proportional to the size and volume fraction of the dispersed phase. Therefore, local changes in concentration ( sedimentation ) and global changes in size ( flocculation , aggregation ) are detected and monitored. Of primary importance in
176-688: The River Thames , River Lea and River Colne ): Chalk streams of the Yorkshire Wolds : Chalk streams of Lincolnshire : There are several chalk streams in the Lincolnshire Wolds including Chalk streams of Kent: Chalk streams of Norfolk: Chalk streams of Suffolk: Suspension (chemistry) In chemistry , a suspension is a heterogeneous mixture of a fluid that contains solid particles sufficiently large for sedimentation . The particles may be visible to
198-603: The chalk stream environment; unpolluted water, healthy and appropriate weed growth and good fly hatches. Thirdly, to enhance the Society's libraries and archives. The first meeting of which the Minutes survive took place on 2 November 1837, and at this meeting it was resolved to have a card engraved for presentation to members. This card bears the inscription: The Piscatorial Society – Established 16th October, 1837 – For promoting friendly intercourse and mutual information among
220-420: The naked eye , usually must be larger than one micrometer , and will eventually settle , although the mixture is only classified as a suspension when and while the particles have not settled out. A suspension is a heterogeneous mixture in which the solid particles do not dissolve , but get suspended throughout the bulk of the solvent , left floating around freely in the medium. The internal phase (solid)
242-426: The 210 rivers classified as chalk streams globally, 160 are in England. A list of chalk streams in England gives a total of 224. Chalk is a highly porous and permeable rock, and rain falling onto chalk topography percolates directly into the ground, where the chalk layer acts as an aquifer . The groundwater flows through the chalk bedrock, re-emerging lower down the slope in springs . The chalk acts as
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#1732800821366264-399: The UK has caused the chalk streams to dry up. This has caused ecological damage and stagnant sewage that flows through the rivers and increasing phosphate levels. 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
286-480: The analysis of stability in particle suspensions is the value of the zeta potential exhibited by suspended solids. This parameter indicates the magnitude of interparticle electrostatic repulsion and is commonly analyzed to determine how the use of adsorbates and pH modification affect particle repulsion and suspension stabilization or destabilization. The kinetic process of destabilisation can be rather long (up to several months or even years for some products) and it
308-431: The basis of the dispersed phase and the dispersion medium , where the former is essentially solid while the latter may either be a solid, a liquid, or a gas. In modern chemical process industries, high-shear mixing technology has been used to create many novel suspensions. Suspensions are unstable from a thermodynamic point of view but can be kinetically stable over a longer period of time, which in turn can determine
330-514: 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 ), 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 life and characteristic transparent shallow water make chalk rivers and streams particularly suited to fly fishing. Many of
352-559: The chalk stream springs are also used as sites for watercress production, due to the constant temperature and clean, alkaline , mineral-rich spring water. The Mid Hants Watercress Railway in 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 by local and national water utility companies. The over-abstracting of chalk streams by private water companies in
374-436: The dissolved substance (solute) does not exist as a solid, and solvent and solute are homogeneously mixed. A suspension of liquid droplets or fine solid particles in a gas is called an aerosol . In the atmosphere , the suspended particles are called particulates and consist of fine dust and soot particles, sea salt , biogenic and volcanogenic sulfates , nitrates , and cloud droplets. Suspensions are classified on
396-436: 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 , potassium and silicate . In addition to algae and diatoms , the streams provide a suitable habitat for macrophytes (including water crowfoot ) and oxygen levels are generally supportive of coarse fish populations. Of
418-443: The head of a pike ), the society now concentrates on fishing for brown trout and grayling with upstream dry fly or unweighted nymph imitations dressed lightly in the style of G. E. M. Skues . The Society has, at its core, three key objectives. First, to maintain a fellowship of flyfishers and the tradition of flyfishing , where possible, for wild or naturalised brown trout and grayling . Secondly, to preserve what remains of
440-523: The lovers of the Art of Angling -Held at the 'Marquis of Granby,' South Audley Street " The decorated chair in the picture at the head of the table still exists along with many other original artefacts and books. The Club Secretary is Geoff Fleming. Chalk stream The beds of the rivers are generally composed of clean, compacted gravel and flints , which are good spawning areas for Salmonidae fish species. Since they are fed primarily by aquifers ,
462-470: 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 grade sediment particles. 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
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#1732800821366484-757: The term stream . The Somme in northern France is a chalk stream on a larger scale. Winterbournes are known by different names depending on region: Chalk streams of the Southern England Chalk Formation in Berkshire , Hampshire , Wiltshire , Dorset and the Isle of Wight : Chalk streams of the Southern England Chalk Formation in the Chiltern Hills , Hertfordshire and Surrey (tributaries of
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