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The potential impact of climate change with regards to groundwater quality has been on the forefront of climate change research over a century now, though there was some short comings on the research approach, (IPCC, 2001). Floods and droughts are considered to be the main effects of climate change affecting groundwater resources, (UKCIP09 projections). The equilibrium state of surface water quality and positions are one of the observable understandings of climate change impact (Winter, 1983), in recent times there has been so much worry by government, managers of water company and the public on the declining nature of groundwater quality supplied; due to its relevance for agricultural produce and for human consumption, (Bear et al., 1999).
This growing trend has culminated to a point that the European Commission Legislation took steps through the; Water Framework Directive and the Nitrate Directive in Europe in recognising the need for a holistic approach in evaluating the hydrological parameters of regional landscapes and consequences it will create on groundwater quality in the future, (Holman, 2006).Climate change effects on groundwater quality can be attributed to ambient temperature with a higher percentage of hydrological events, (Delpla et al., 2009). It is of the view that the physico-chemical equipoise differs in temperature, which constantly elevates endothermic responses, (Delpha et al., 2009). Consequently, the changing processes in water are supported by water temperature elevation of 10 â°C like; evaporation, degradation, dissolution, solubilisation and so on, (Bates et al, 2008). This trend comprehensively tends to the convergence of elevated dissolved materials in water and also with the convergence of reduced dissolved gases, (Bates et al, 2008). These last views are vital with regards to dissolved oxygen in water. The climate change impact in the United Kingdom is felt in an alarming situation in the southeast region of England compared to anywhere else, (Merylyn M).
This Project is a study of the impact of climate change on the groundwater quality of the Patcham catchment, located in South Downs of Brighton, Southeast of England. This catchment area is predominantly Chalk formation. In this region the Chalk and the Lower Greensand are the main aquifers; which is the route of supply of about 75% of water to the populace in the south downs of Brighton and environs (http://southdownsonline.org). This aquifers differ from floods, drought and saline situation within a space of time, which may metamorphous into the alteration of the groundwater quality in the spring channels as they increase in discharge on likely consequences from ecological position (G. Darling et al), this is due to the fact that water migrate into the groundwater body; which is an hydrologic process influenced by surface water factors or precipitation that is dominated by climate change thereby making the groundwater structure vulnerable, (Michael W.T., 2003). The South Downs Chalk aquifer of Brighton is compactly taken advantage of over the years, (Robins et al., 1999). Since the early 50's the groundwater resources of the South Downs region has encountered series of saline intrusion; due to abstraction of groundwater especially in lengthy dry season and also the problem of urbanization; which also affects the quality of the groundwater, (Robins et al., 1999). In 1978 an Aquifer Protection Policy was introduced to address this crisis in whose procedures the Southern Water Authority in 1985 endorsed a management program for the groundwater resources in the region that later culminated in the borehole system in monitoring and managing the climatic and ecological situation on the groundwater quality, (Robins et al., 1998). However, there has been a perceptive view scientifically on the reaction of aquifers to climate change examined over the past ten years in a number of areas which proofs that there is a connection between unsaturated soil structure and atmospheric structure, which subsequently progress to a groundwater structure, (Michael W. T., 2003).
1.1 AIMS AND OBJECTIVES
The objectives of this project is to use the data provided by the Environmental Agency's Groundwater quality Monitoring Network (GWQMN) through the CLIMAWAT to explain the factors affecting the groundwater resources with respect to the direct and indirect effects of present and future climatic change on the groundwater quality from the catchment of Patcham. Groundwater is a significant water source in Brighton whose quality is essentially important for usage because 98% of water supplied to the public is gotten from the Brighton Chalk aquifer, (Environmental Agency, 2005).
The primary focus of this project is on the following areas:
The characteristics of major units
Recharge and Groundwater flow
The trends in the Groundwater quality.
2.0 Geographical Location
2.1 Catchment Area
This project is on the Patcham catchment area situated in Brighton, southeast of England. It covers an area of about 40 square kilometre with about 65m elevation and is located between the Ouse and Adur rivers (Adams et al, 2008), it has a GPS 318/333 systematic mapping of the BGS (British Geological Survey) 1:50.000 of Brighton and Worthing combined sheets, (BGS, 2006) and also with from the Pyecombe borehole core results situated at the north of the catchment (fig 1). From the Patcham valley sequence the Pyecombe borehole core shows the composition of the Lewes nodular chalk, while in the St Peters church and Victoria gardens borehole shows a composition of Seaford chalk adorning the Lewes nodular chalk and the Lewes nodular chalk adorns the new pit chalk, (BGS, 2006) (fig 3).
2.2 Topography and Geomorphology
The South Downs has terrains that consist of Chalk formation and a geomorphological past of cretaceous and quaternary deposits which consist of periglacial dry valleys, (Lord et al, 2001). The Chalk was exposed to both mechanical and chemical weathering by diversity of climatic condition until it was uplifted in early Tertiary period (Lord et al, 2002). During Quaternary age the Chalk went through severe degrading process by different types of weathering and modification factors which then culminated to new deposits covering the degraded Chalk , (fig 3) (Mortimore and Duperret, 2004).
The outcrop of the Chalk consists of disintegrated Wealden Anticline which is responsible in the shaping of the southern province, (Environmental Agency, 2008). The South Downs embankment line consists of very high grounds of about 200m that goes through from East to West aligning to the borders of the north, (Lloyd, 1993). The embankment line of the South Downs has fractured features that create a channel from where the Rivers Ouse and Adur run through, (Dr. Derek Langslow). There are features of revealed Chalk formations in this area that spills in the direction of the coast, though there is a rolling downland of dip slope which are caused by cuttings of dry river valleys; like the southern part of Falmer which has an elevated landscape that outlines dry valley associating it with the north, (Environmental Agency, 2008). To the West of Brighton and the coast are levelled lands which shape the coastal plains with the steep cliff land of Brighton adjoining the coast to the East, (Dr. Derek Langslow). The chalk formation around the Brighton area is made up of a variation of thickness with lithology of deep thrust fault, surface fracturing and folds, (Mortimore et al, 2001).
The geomorphology of the Patcham catchment is characterised by mature landscape that has great relief topography (Adams et al, 2008) in which each Chalk formation has his geological characteristics that creates a distinctive topographical feature with slop changes (fig.2), (Lord et al, 2002, pp.26). The South Downs Chalk has a dominating influence on the Catchment topographic setting, down to the south of the catchment and furthermore to where the land slops to the shoreline, (Environmental Agency, 2007). Alongside Sussex costal area the entire stratigraphy of the Chalk appear showing different lithological sequence of the Chalk formation which is advantageous in correlation making (fig.4a), (Mortimore et al, 2004). There are structural sequences of visible surface karstic features around the catchment location which entails: the occurrence of dolines and stream sinks which is a significant sign of improved aquifer features, (Mortimore, 1990; Edmond, 1993; Banks et al., 1995), and they are mainly situated on the Upper Chalk edge with Palaeogene deposits adorning it, (Jones et al., 1999). An extensive Palaeogene cover is seen in (fig 4a). The dolines are seen (fig 4) in locations where clay-with-flints deposits overlie areas of chalk, there are also small karst surfaces order than dry valleys where the chalk outcrops (BGS, 2001), though the karst features on the study area determines the distribution of elevated transmissivity of contaminant within the aquifer, (Atkinson and Smart, 1980). The hydrological actions to a large extent facilitate the topographic transportation of elevated transmissivity, though lithological elements are considered to establish irregularities like deep fissure with elevated transmissivity far from the valleys of the rivers, (Allen et al., 1979).
The South Downs is one of the most temperate and bright regions in England having summer and winter of 16.1â°C to 5.5â°C of temperature ratio; the region gets a modal value of sunshine in a day for seven hours in summer, it also has a yearly rainfall within the values of 844mm with its topography controlling the circulation, (Jones et al., 1999).
The Brighton Chalk Groundwater Body obtains more than 25% precipitation compared to any coastal region in England, (Jones et al., 1999). The evapotranspiratory mean value is 485 aÂ¯Â¹, (Southern Water Authority, 1984). During the drought of 1975 and 1976 the recharge was between an average range of 40 - 50% and with the drought of 1988/1992 having a recharge medium ratio of 50 -70% throughout that particular time, (Marsh and Monkhouse, 1993).
2.4 The Land Use
The soils formed on the chalk are of Andover 1 Association according to the soil survey of England and Wales, (1983) which are characterised by rocky surface rendzinas which consist of a mixture of clay, sand, organic matter and silty clays, (Boardman, 2001). The Downs soil consist of strong loess cover (fig 4) which was build up in the Devension masses of ice (Favis-Mortlock et al, 1997).
During the last 5000 years, there has been a gradual removal of loess cover due to persistent anthropogenic removal of forest and a steady heightening of agricultural activities, (Favis-Mortlock et al, 1997). This area has a history of erosion due to the development of the soil on Chalk, (Environmental Agency 1999 & BGS 1999).
The South Downs has three major classification of Land Use which is;
the Coastal zone
and the Scarp face
The Coastal zone is mostly urbanised in the north of Brighton, the Downs is dominated by a combination of arable farming mostly cereals crops, a little of peas and rapeseed and the Scarp face which has a steep nature but rich in vegetation; which is employed for the feeding of ungulate livestock, (Jones et al, 1999).
The cultivation of grass land for the production of cereal crops most especially in winter by famers in the early 1970's and 1990's in the south downs took a hike, (Boardman, 1990), this led to an increase in the collective application of modern technology for growing crops; thereby heightening the application of agrochemicals; like pesticide, chemical fertilizers and also the use of manures from Animal waste (NRA, 1992). This scenario resulted in millions of tonnes of fertilizer nutrients being produced per annum, (NRA, 1992). Base on this fact, the need to safeguard the groundwater from nitrate intrusion and contamination like the organic and inorganic fertilizer mostly from agricultural source was championed by the EC Nitrate Directive (91/6676), (Heathwait et al., 1993). Furthermore, the cultivation processes by farmers encouraged by the UK government after the war lead to the deterioration of the soil; creating huge gullies due to wheel tracks of big machinery (Evans, 1990), animal stampings, forestry activities, fire events, even human activities all of which promotes runoff that creates a trend for erosion (Evans, 1997), thereby culminating to the deterioration and sedimentation of the groundwater quality in the region, (Butcher et al, 1993).
The South Downs has a yearly rainfall of 1000 to 105mm and 700mm in the coastal region, while in Brighton the minimum rainfall yearly is 800mm and the minimum yearly recharge is 475mm, this particular region of the south of England is tagged as number three in the most driest, (Environmental Agency, 2005) whose lithological situation accounts for how rainfall is managed, (J.C. Radda).
The Groundwater body of the Brighton Chalk is bordered by the river Adur and river Ouse to the east and to the west, (Environmental Agency, 2008). These rivers are excessively cut downwards through its river banks and later covered with deposits of alluvial. These rivers are under the grading of estuarine, (BGS, 1978) with a plethora of 1000mg/l due to the convergence of chloride flow which is as a result of tides of the rivers moving further to the northern part of the Groundwater body of the Brighton Chalk (Environmental Agency, 2008). The outcropped Chalk has no top water layer due to the hydrological setting of the soil and due to the deepness of the water table which indicates that there is a situation of vaporization or percolation of rainfall, (Environmental Agency, 2008).
3.0 GEOLOGY OF THE AREA
3.1 Main Groups and Formations
The South Downs of the United Kingdom is mostly of Chalk formation that has one of the main aquifers which provides the civic and rural areas with groundwater supply to approximately 700,000 people majority of which resides in the coastal margin from Chichester, Portsmouth, Worthing, and Eastbourne to Brighton, (Jones et al, 1999). Chalk is a micritic limestone with a whitish colouration that originated from living organism, mostly detritus from calcareous, (Wrag 1999 and Mortimore et al 2001).
The Groundwater Body of the Brighton Chalk is made up of two Subgroups: the Grey and White Chalk Subgroups which is the same in the category of the Lower, middle and upper Chalk grading, (Hopson, 2005). The Grey chalk Subgroup: is practically flintless, in some of the areas the formation has been shared into two; the Merly Chalk and the Zig Zag Chalk, (Bristow et al) which is based on the Dorset initial mapping that is now applied throughout the Southern region, though this location has a wide spread erosive bed, (Mortimore et al., 2001). The Merly Chalk which is situated in the Lower Chalk which is characterised by Gluoconite marl at the bottom which is placed over the Chalk Marl to the point where it reaches the Tenius limestone at the bottom. It has a milky white marls with a brownish pale grey limestone and Chalks that are greyish at the layer on top of the base, while the Zig Zag Chalk which comprises of strong fossiliferous Chalk and ammonite which is also of the Tenius limestone is placed at the bottom consisting of Plenus marls which ( 60 - 75m in hardness around the groundwater matter of the Brighton Chalk), (Environmental Agency, 2008) is placed on top surrounding the Chalk marl and Grey Chalk at the top, having a strong rough Chalk with a hardness of 2m making a characterised pattern on the Grey Chalk base, (Jefferies, 1963).
The White Chalk Subgroup: this subgroup is made up of; the Lewes Chalk, Seaford Chalk, Newhaven Chalk and the Tarrent Chalk according to the Groundwater Body of the Brighton Chalk, (Environmental Agency, 2008). The features of the formations shows that there are dominating parameters of nodular chalks, flints and marls in the geology with a significant sedimentary unconformity in the Groundwater Body of the Brighton Chalk that has a hardness of 150 - 250m(BGS, 1978). In the Tarring Neville trough, the Shoreham trough and the little Caburn trough under the Lewes Chalk stretching to the eastern part of Brighton are higher levels of Chalk hardness, (Environmental Agency, 2008).
From the top of the Gault clay to the north surrounding the groundwater body of the Brighton Chalk forming an impervious obstruction to vertical flow of groundwater (fig 4), this groundwater matter is made up of the Upper Greendsand; which is composed of a range of hard soil due to climatic condition, which has a smooth-grained glauconitic silty sands with sandstone, slight layer of Quaternary and Chalk, (Environmental Agency, 2008).
In fig 4, Shows the superficial deposits in the coastal stretch on the small path to the direction of the south west of the location on top of the Chalk are numerous beach sediments, brick earth and head deposits (Environmental Agency, 2008). These varieties of flinty loams sandy gravels, loamy silts and clays stretches to about 2km to the interior while fading out east side of Brighton (Environmental Agency, 2008). In some other places, little units of clay with flints which is one of the characteristics of outcrops of White Chalk Subgroup is on the upland connecting the rivers Ouse and Adur in a drainage network with alluvium on its path, also in the dry high lands of the confined Head deposits are units of dry valleys one of which is the Falmer uplands being the significant, (BGS, 1999).
However, the small outcrop of the Rending Beds and the Woolwich has been discovered as formations separated by erosion with a thickness of 8m which is on the dip direction of the Chalk close to Newhaven, Seaford and Brighton, (Jones et al, 1999).
3.2 The Catchment Geology
The geological succession and geomorphology of this catchment area has been investigated previously, (BGS Flood 1, 2006).
It has been shown in the Flood 1 report (2006) that there are many tight folds due to the crossing on the lines of two fold axes with faults and karstic features on the chalk formation which belong to the White Chalk subgroup that is aligned to the upper chalk classification; Quaternary deposits, which have been geologically recognised in the study area, stratigraphically it is described as:- clay-with -flints; formulated due to weathering deposits from Eocene forming a loosed seeping brown earth, mostly with small loose calcium carbonate that has a value of (6.3<pH<7.7), (Michael. J) also with numerous nodular and rounded flints with a structural geology manifested as a combination of trough and domes with occasional large-scale faults having loess deposits capping the chalk around the study area which spreads across the Newhaven formation to the Seaford formation (fig 4), (Mortimore et al, 2001).The main formations that covers the Patcham catchment are the New Haven Chalk, Seaford Chalk, Culver Chalk and Lewes Nodular Chalk members, (Mortimore, 1987), though at the north of the Patcham catchment which is close to the Pyecombe Catchment is characterised by the New Pit Chalk formation, (Flood1 Report, 2006).
Characteristics of the Formations:
The Newhaven Chalk formation is characterised by blocky white chalk with marl seams of a ratio of 45 to75 in thickness, though it has a scanty amount of flints seams, it is frequently scattered along the marl seams and it is highly fractured due to conjugated joint set, (Barry et al).
The Seaford chalk formation has approximately 50 to 80m thickness of white chalk with bands of immense nodular, semi-tubular and sheet flints with little marl seams having persistence orthogonal and bedding parallel joint set, (Barry et al).
The Lewes Nodular Chalk has a cadenced order of soft chalks with a hardness of 35 to 40m, (D, Allen) with thin marls, nodular chalk and persistence of flints visibility, (BGS). The ground hardness of this member can be seen mostly dominating at the surface and the base lies in the erosion surface that is under the Glynde marl, (Young et al, 1988).
The Culver Chalk formation is made up of fine soft white Chalk with marl and lots of big nordular flints with a thickness range of 65 to 75m, (Wilkinson et al., 2008).
The New Pit Chalk formation comprises of hard white Chalk that has lots of recurring marl seams having a thickness of 25m, (D, Allen).
4.1 The Hydraulic Nature of the Chalk
The Chalk enormous outcrop with its porosity nature and compactness gives it a huge area that has remarkable depositary capabilities which places it as the most significant aquifer in the whole of the southern region of England, (Headworth and Fox., 1985). The Chalk lithological nature is of white, soggy finite limestone of fine grain that has marl seams, nodular, bands of tabular flint and nodular beds which has a state of hardness after undergoing numerous changes due to previous erosion activities which are in a large margin value of about 330m underneath the Tertiary overlay of about 150 to 300m through the outcrop parameter, (Headworth and Fox., 1985).
There are three fold sectionalisation of the Chalk that is properly categorised into the lower, middle and upper formations, although new maps now shows that the South Downs borders between the formations of the middle and upper Chalk which is very complex to understand which might be unacceptable to others, (Headworth and Fox., 1985). However, due to this development a remapping survey was done by the BGS to put all the formations into one group which was later called the Sussex White Chalk, (Mortimore, 1979, 1983).
In the hydrogeological sense, this particular formation is the most significant means of groundwater flow in respect to water utility, though the water supplied through the lower Chalk is known to be clayey making it deficient in nature, (Headworth and Fox., 1985). The out flux situated at the north emerge through a clear and delineated enduring spring path almost on top to the bottom part where the Lower Chalk is situated, (Headworth and Fox., 1985). However, the location of springs on the dip slope of the gentler changes depending on the season in reaction to filtration which increases streams irregularly, (Headworth and Fox., 1985).
Finally, the Chalk structure of a formation has a significant impact on the hydrogeology of a Catchment which can be influenced by a series of syncline folds and anticline activities, e.g. Brighton and Worthing blocks, (Headworth and Fox., 1985).
4.2 Characteristics of the Core Components
The Chalk formations of the South Downs is composed of lots of inconsistency so much that it influences the spreading of major fractures to the level of disintegration resulting to fracture expansion, (Price, 1987, Mortimore, 1993). The Chalk undergoes a diagnetic transformation induced by activities such as Tectonic force, heat and burial which is followed by compression which has solidified the Chalk degrading the matrix porosity, (Jones et al., 1999). Due to these trends of transformations, the South Downs Chalk porosity of the matrix is within a sequence of 15 - 45%, with a 10Â¯â´- 10Â¯Â² m dÂ¯Â¹ hydraulic conductivity, (Jones et al., 1999).
The flux of Groundwater in the South Downs is mainly from the north to the south, showing the different topographic features and planes with the discrepancies in porosity, (Jones et al., 1999). The area has a geological composition that is characterised by the effect of hydrogeochemistry and hydrogeology activities (Jones et al., 1999) such as the syncline of Chichester which hampers the southward flux of groundwater redirecting it eastward with Palaeogene deposits filling the spaces of the enclosed syncline in the Chalk groundwater of the region, (Jones et al., 1999).
The Chalk of the Brighton Groundwater Body aquifer is basically unconfined apart from outlying areas that is small connected to patches of Palaeogene overlay with slide in the direction of the major river dale to the direction of west of the coast of Brighton, (Environmental Agency, 2007). The Groundwater recharge is believed to arise moderately in a uniform manner over the opened Chalk regardless of the kind of soil, (Environmental Agency, 2007). Groundwater is the main channel to which the rivers Ouse and Adur obtain their flows; though it is only in severe measures of the removal of groundwater do movement of water take place out of the rivers to the encompassing aquifers, the altitude of the Groundwater lacks depth which gravitates to show the topography of the area, (Environmental Agency, 2007). Hydraulic gradients in this area are mostly in the direction of the coast line having secondary flux to the direction of each of the rivers, (Environmental Agency, 2002).
4.3 The Unsaturated Zone of the Chalk
The Chalk of the South Downs aquifer is adorned with cavernous unsaturated zones having features of huge permeable matrix with binary porosity systems, (www3.imperial.ac.uk). The structure and size adorning the aquifer by the vadose or unsaturated zone has a significant relevance to how liquids infiltrates to the aquifer through the surface to the ground, (Granyham et al.).
4.4 Hypothesis of the unsaturated zone
It is of the opinion that movement of liquid in the unsaturated zone is as a result of fractures in the Chalk, (Mathias et al, 2005). The prompt reaction of water table to an elevated severity of rainfall activities and the development of bacteria in construction boreholes have been viewed as a proof for all of the anticipated presumptions, (Mathias et al, 2005).
In an investigation on the tritium constituents present inside the water orifice of the Chalk finalised that the overall flux via the unsaturated zone is about 85% which is mostly from the intergranular flux via the matrix (< 0.9m/year), (Smith et al., 1970). The outcome of Smith et al, (1970) findings initiated a Piston flux notion through which the swift reaction of water level was understood on the concept of water going through a Piston process having a change in magnitude and direction inside the unsaturated zone instead of the flow of water via the unsaturated zone, (Price et al., 1993). Although, Mathias et al (2005) reiterated that there have been different opinions regarding the findings of Smith et al (1970), arguing that if the flow of liquid inside the matrix aeration zone or unsaturated zone of the Chalk is important? However, a research approach was undertaken by Mathias et al (2005) which arrived at a decision stating that the flux of water inside the matrix of the Chalk unsaturated zone is important, not paying attention to it might culminate into a difficult mix up of what the system entails. It is also noted that the use of stead state method for a research designs by the authors was not proficient enough to evaluate the overall capacity of infiltration on the matrix annually, (Flood 1 Report, 2007). Recent expenditure on several Chalk locations around the Southeast propose that the flow of liquid through the fractured features may probably arise when matrix capacity goes high about - 50hPa, although, it was discovered that going beyond this value will amount to a hike in hydraulic conductivity as translated due to the system of fracture controlling the flow of water, (Wellings, 1984).
From this investigation, a study of Fleam Dyke lysimeter data from Cambridgeshire illustrates that a swift drainage value that is > 1mm/day - the matrix of the hydraulic conductivity obtained took place via the lysimeter (a solubility instrument) was > - 50hPa in capacity as at 5m review, (Jones and Cooper, 1998). It is of the view that in this location the flow of water through the fracture estimates a yearly drainage of about 30%, (Flood 1 Report, 2007). Moreover, in Hampshire, Bridget's farm, the hydraulic conductivity matrix which has an elevated value between 6mm/day whose matrix capacity was moved high - 50hPa due to unprecedented rainfall activities, although the flow liquid through the fracture features are considered unusual occurrences based on absorption, (Wellings, 1984).
Also, in a survey carried out on a Chalk catchment by two rivers was discovered that the discharge of water from the catchments which is under downturn was relatively higher than what would be defined by the removal of water from the Chalk as a result of gravitational force through the pores, (Lewes et al., 1993). However, it was finalised that the variations witnessed was based on a gradual discharge of water in the unsaturated zone through the Chalk drains, (Flood 1 Report, 2007). Furthermore, it was estimated that a similar drained water with a value of about 0.25 - 0.30% in range of rock mass of the unsaturated zone will be enough to ignite such irregularity, (Flood 1 Report, 2007).
Although, this finalisation conflicted the views that pore matrix cavities do not carry water to considerable measure around the matrix because of tiny spaces of pore units, (Price et al, 1993). Not long ago, a study was undertaken at the Bridget's Farm location in 2000 and 2001, stating a situation of higher occurrence of recharge in winter while the unweathered Chalk in the unsaturated zone with a dept range of 3m - 8m has a huge elevation of accumulated water, (Roberts and Rossier, 2006). The elevation of water in the unsaturated zone was constant with a time frame which implies that the Chalks unstable nature is more than what has been earlier anticipated, (Flood 1 Report, 2007).
It was finalised after a summary of studies carried out by various authors by Price et al, (2000) that variations in reservoir accountable to water highlighted by Lewes et al, (1993) is situated on the fissure covering around the unsaturated zone that is very unsteady. The reason for water table dawdling reaction to recharge occurrence during periods of recharge was due to increased storage which is also a reason for Chalks elasticity nature when it comes to drought situations, (Flood 1 Report, 2007). Haria et al, (2003) stated that on a parallel fracture there is an accumulation of water which is as a result of film build up at spots connecting amidst upright blocks on top of one another. Furthermore, there is a build up of a tiny water film at the connecting spots which harbours the rise of upright flow of water, (Hodnett and Bell, 1990). Finally, in conclusion to what Price et al, (2000) illustrated, the parallel fracture features are responsible for substantial amount of water stored inside an unsaturated zone.
From Flood 1 Report, (2007), there are three flow mediums of water via an unsaturated Chalk; -
The hydraulic conductivity behaviour of a Chalk based on these mediums is;
The flux of water via a matrix takes place at a point where there is reduced matrix capacity
If a matrix capacity peaks there will be a pressure oscillation which will change the level of recharge from lower margin to a higher margin. This scenario may take place when the porosity in the matrix is completely saturated.
The flux of water via fractures would take place if the matrix capacity is greater compared to a higher value of recharge. The function of the film flux is to ensure that there is movement of water where matrix capacity is reduced.
A survey by Downing et al, (1978) revealed that the convergence of tritium with water heights on three boreholes around the Groundwater Body of Brighton Chalk, Patcham inclusive, shows that there is a reality of a swift flux via the unsaturated zone whose thickness range of approximately 20 - 40bgl estimating that it is equivalent to 10% of recharge yearly. It is of the view that most of the flux takes place via a bigger orifice in the micro/matrix fissure, (Jones et al., 1999). It is also ascertained that the tritium estimate evaluated in all the boreholes at recharge occurrence shows an elevated margin compared to the value recorded for rainfall; indicating that water recharge will derange the older water pared down in the analysis through the medium of the Piston flux, (Jones et al., 1999). According to the survey, it is obvious that the system of recharge in the aquifer differs to a large extent through the South Downs with an outcome of uncertainty in results between locations, (Environmental Agency, 2007). Consequently, the extensive changes in the elevation of Groundwater between the Brighton Groundwater Body and the Worthing Groundwater Body which are between the same rivers drainage with water standing that has a variation of 21m implying low retention even little quantity of recharge give rise to major water variations, (BGS, 1999).