Chalk aquifer - Revision history

Editor at 12:00, 18 January 2022

2022-01-18T12:00:17Z

← Older revision		Revision as of 12:00, 18 January 2022
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	* Groundwater control in urban areas.		* Groundwater control in urban areas.
	* Holloway.		* Holloway.
		+	* How adaptive planning is being used to future-proof water supplies in the South East.
	* Isotropic.		* Isotropic.
	* Thames barrier.		* Thames barrier.

Editor at 14:49, 9 November 2021

2021-11-09T14:49:33Z

← Older revision		Revision as of 14:49, 9 November 2021
Line 60:		Line 60:
	* Groundwater control in urban areas.		* Groundwater control in urban areas.
	* Holloway.		* Holloway.
		+	* Isotropic.
	* Thames barrier.		* Thames barrier.

Editor at 14:39, 9 November 2021

2021-11-09T14:39:59Z

← Older revision		Revision as of 14:39, 9 November 2021
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	= Related articles on Designing Buildings =		= Related articles on Designing Buildings =

		+	* Anisotropic.
	* Aquifer.		* Aquifer.
	* Aquitard.		* Aquitard.

Editor at 18:26, 8 November 2021

2021-11-08T18:26:34Z

← Older revision		Revision as of 18:26, 8 November 2021
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	The GARDIT strategy achieved its goal in 2000, however, subsequent data suggests levels will require continual artificial management.		The GARDIT strategy achieved its goal in 2000, however, subsequent data suggests levels will require continual artificial management.

−	= Related articles on Designing Buildings ~~Wiki~~ =	+	= Related articles on Designing Buildings =

	* Aquifer.		* Aquifer.
		+	* Aquitard.
	* Clunch.		* Clunch.
	* Fertilizer groundwater pollution.		* Fertilizer groundwater pollution.

Editor at 16:24, 11 March 2021

2021-03-11T16:24:41Z

← Older revision		Revision as of 16:24, 11 March 2021
Line 57:		Line 57:
	* Groundwater.		* Groundwater.
	* Groundwater control in urban areas.		* Groundwater control in urban areas.
		+	* Holloway.
	* Thames barrier.		* Thames barrier.

Editor at 18:30, 11 December 2020

2020-12-11T18:30:35Z

← Older revision		Revision as of 18:30, 11 December 2020
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	* Aquifer.		* Aquifer.
		+	* Clunch.
	* Fertilizer groundwater pollution.		* Fertilizer groundwater pollution.
	* Flint.		* Flint.

Editor at 19:45, 29 September 2020

2020-09-29T19:45:16Z

← Older revision		Revision as of 19:45, 29 September 2020
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	* Aquifer.		* Aquifer.
	* Fertilizer groundwater pollution.		* Fertilizer groundwater pollution.
		+	* Flint.
	* Groundwater.		* Groundwater.
	* Groundwater control in urban areas.		* Groundwater control in urban areas.

Designing Buildings at 05:57, 11 September 2020

2020-09-11T05:57:55Z

Editor at 18:43, 9 September 2020

2020-09-09T18:43:44Z

← Older revision		Revision as of 18:43, 9 September 2020
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	{\|		{\|
−	~~\|width="100%"~~\| [[File:ChalkAquifer.jpg]]	+	\| [[File:ChalkAquifer.jpg\|link=File:ChalkAquifer.jpg]]
	\|-		\|-
	\| After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to rise in many springs and pools. In 2014, the westernmost sources of the Pang rose beyond West Ilsley, and the usually dry upper sections of the Pang flooded roads and houses in all the villages along its course.		\| After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to rise in many springs and pools. In 2014, the westernmost sources of the Pang rose beyond West Ilsley, and the usually dry upper sections of the Pang flooded roads and houses in all the villages along its course.
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	= Characteristics of the Chalk aquifer =		= Characteristics of the Chalk aquifer =

−	The Chalk aquifer has an interconnected network of fractures. Yields of approximately 150 litres per second are the ~~greatest~~ where the density of fractures is greatest and/or where the fractures are enlarged. Most of the Chalk aquifer's storage comes from the secondary porosity of these fractures.	+	The Chalk aquifer has an interconnected network of fractures. Yields of approximately 150 litres per second are the highest where the density of fractures is greatest and/or where the fractures are enlarged. Most of the Chalk aquifer's storage comes from the secondary porosity of these fractures.

	Made of microporous white limestone with layers of flint, the Chalk is a type of calcareous clay. Its composition also includes shells along with small fragments of plankton.		Made of microporous white limestone with layers of flint, the Chalk is a type of calcareous clay. Its composition also includes shells along with small fragments of plankton.

Editor: Created page with "{| |width="100%"| File:ChalkAquifer.jpg |- | After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to r..."

2020-09-09T18:37:54Z

Created page with "{| |width="100%"| File:ChalkAquifer.jpg |- | After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to r..."

New page

{|
|width="100%"| [[File:ChalkAquifer.jpg]]
|-
| After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to rise in many springs and pools. In 2014, the westernmost sources of the Pang rose beyond West Ilsley, and the usually dry upper sections of the Pang flooded roads and houses in all the villages along its course.
|}

= Introduction =

An aquifer is a geological formation that holds groundwater. The term 'groundwater' refers to all water which is below the surface of the ground and within the permanently saturated zone. A groundwater body is a distinct volume of groundwater within an aquifer, which is sufficiently porous and permeable to store and yield a significant quantity of water to a borehole, well or spring.

The properties of aquifers depend on their composition. The most important properties are porosity and yield. These characteristics dictate the aquifer’s capacity to release water through pores and influence its ability to transmit water.

= What is the Chalk? =

There are chalk aquifers throughout the world. However, one specific chalk aquifer, know as the Chalk, is the major aquifer of southern and eastern England. It supports the Thames Basin and the London aquifer.

The Chalk stretches from the south east portion of Yorkshire south into Lincolnshire. It spans across central southern England from north Norfolk through the Thames Basin and along the Kent coast to the Isle of Wight and into Dorset. It is associated with the iconic scenery of the white cliffs in and around Dover.

= Characteristics of the Chalk aquifer =

The Chalk aquifer has an interconnected network of fractures. Yields of approximately 150 litres per second are the greatest where the density of fractures is greatest and/or where the fractures are enlarged. Most of the Chalk aquifer's storage comes from the secondary porosity of these fractures.

Made of microporous white limestone with layers of flint, the Chalk is a type of calcareous clay. Its composition also includes shells along with small fragments of plankton.

Its unusual structure has well developed fissures that are between 0.5 to 2% of their total volume, giving them a higher permeability. It also has low matrix permeability, which prevents water from draining quickly.

= Vulnerability =

Problems may occur in places where porewater found in the Chalk aquifer contains saline (such as in the Thames Basin and across East Anglia). In some regions, this can result in contamination of groundwater, particularly in areas where excessive aquifer pumping takes place.

The Chalk aquifer is susceptible to pollution from nitrates and other pesticides associated with agricultural activity. It can also become contaminated by industrial chemical accidents resulting in leakage.

However, due to the long “lag-time” (it can take up to 40 years before undesirable pollutants leach into the soil and enter the water supply), the Chalk has been subject to specialised engineering models that simulate how these toxic materials work their way into the groundwater. Modelling has influenced decisions to increase investment in in-situ aquifer treatment as a solution in the Chalk region.

= The London Basin Chalk Aquifer management plan =

In August 2018, the Environment Agency released a status report on the management of the London Basin Chalk Aquifer. The reports, which began in the 1990s, were meant to document the rise in groundwater levels. They also outlined a management plan to protect the aquifer as a sustainable, secure and high quality water resource while protecting the infrastructure from floods and other structural damage.

The report found that reduced groundwater levels have eroded the natural groundwater outlet in the centre of the London Basin. This has resulted in the intrusion of saline river water from the tidal Thames and could lead to the release of sulphate-rich, acidic groundwater through pyrite oxidation. The impact of this potential activity requires additional research.

The group of experts assembled in 1992 to manage the London Basin. Referred to as the General Aquifer Research Development and Investigation Team (GARDIT), the group implemented a strategy to arrest the rise in groundwater.

The GARDIT strategy was defined by Thames Water, the Environment Agency, London Underground, the Corporation of London, Envirologic, the Association of British Insurers (ABI) and BT.

The five phases were defined as follows:

* Phase 1 - Thames Water to re-commission disused sources.
* Phase 2 - Thames Water to develop proven existing boreholes.
* Phase 3 - Private, commercial boreholes.
* Phase 4 - Thames Water to create new borehole sites in central area.
* Phase 5 - Thames Water to create new borehole sites in outer area.

The GARDIT strategy achieved its goal in 2000. However, additional data suggests the levels will require the continuation of artificial management in order to maintain them.

= Related articles on Designing Buildings Wiki =

* Aquifer.
* Fertilizer groundwater pollution.
* Groundwater.
* Groundwater control in urban areas.
* Thames barrier.

= External resources =

* Environment Agency, [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/735451/2018_Final.pdf Management of the London Basin Chalk Aquifer].

[[Category:DCN_Definition]] [[Category:DCN_Guidance]] [[Category:DCN_Report]] [[Category:Definitions]] [[Category:Water]] [[Category:Property_development]]

← Older revision		Revision as of 05:57, 11 September 2020
Line 2:		Line 2:
	\| [[File:ChalkAquifer.jpg\|link=File:ChalkAquifer.jpg]]		\| [[File:ChalkAquifer.jpg\|link=File:ChalkAquifer.jpg]]
	\|-		\|-
−	\| After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to rise in many springs and pools. In 2014, the westernmost sources of the Pang rose beyond West Ilsley, and the usually dry upper sections of the Pang flooded roads and houses in ~~all the~~ villages along its course.	+	\| After a winter of heavy rainfall, the chalk aquifer which feeds the River Pang can become saturated, causing the groundwater to rise in many springs and pools. In 2014, the westernmost sources of the Pang rose beyond West Ilsley, and the usually dry upper sections of the Pang flooded roads and houses in villages along its course.
	\|}		\|}

Line 13:		Line 13:
	= What is the Chalk? =		= What is the Chalk? =

−	There are chalk aquifers throughout the world. However, one specific chalk aquifer, ~~know~~ as the Chalk, is the major aquifer of southern and eastern England. It supports the Thames Basin and the London aquifer.	+	There are chalk aquifers throughout the world. However, one specific chalk aquifer, known as the Chalk, is the major aquifer of southern and eastern England. It supports the Thames Basin and the London aquifer.

−	The Chalk stretches from the south east ~~portion~~ of Yorkshire south into Lincolnshire. It spans across central southern England from north Norfolk through the Thames Basin and along the Kent coast to the Isle of Wight and into Dorset. It is associated with the iconic scenery of the white cliffs in and around Dover.	+	The Chalk stretches from the south east of Yorkshire south into Lincolnshire. It spans across central southern England from north Norfolk through the Thames Basin and along the Kent coast to the Isle of Wight and into Dorset. It is associated with the iconic scenery of the white cliffs in and around Dover.

	= Characteristics of the Chalk aquifer =		= Characteristics of the Chalk aquifer =
Line 21:		Line 21:
	The Chalk aquifer has an interconnected network of fractures. Yields of approximately 150 litres per second are the highest where the density of fractures is greatest and/or where the fractures are enlarged. Most of the Chalk aquifer's storage comes from the secondary porosity of these fractures.		The Chalk aquifer has an interconnected network of fractures. Yields of approximately 150 litres per second are the highest where the density of fractures is greatest and/or where the fractures are enlarged. Most of the Chalk aquifer's storage comes from the secondary porosity of these fractures.

−	Made of microporous white limestone with layers of flint, the Chalk is a type of calcareous clay. Its composition also includes shells ~~along with small fragments of~~ plankton.	+	Made of microporous white limestone with layers of flint, the Chalk is a type of calcareous clay. Its composition also includes shells and plankton.

	Its unusual structure has well developed fissures that are between 0.5 to 2% of their total volume, giving them a higher permeability. It also has low matrix permeability, which prevents water from draining quickly.		Its unusual structure has well developed fissures that are between 0.5 to 2% of their total volume, giving them a higher permeability. It also has low matrix permeability, which prevents water from draining quickly.
Line 29:		Line 29:
	Problems may occur in places where porewater found in the Chalk aquifer contains saline (such as in the Thames Basin and across East Anglia). In some regions, this can result in contamination of groundwater, particularly in areas where excessive aquifer pumping takes place.		Problems may occur in places where porewater found in the Chalk aquifer contains saline (such as in the Thames Basin and across East Anglia). In some regions, this can result in contamination of groundwater, particularly in areas where excessive aquifer pumping takes place.

−	The Chalk aquifer is susceptible to pollution from nitrates and other pesticides associated with agricultural activity. It can also become contaminated by industrial chemical ~~accidents resulting in~~ leakage.	+	The Chalk aquifer is susceptible to pollution from nitrates and other pesticides associated with agricultural activity. It can also become contaminated by industrial chemical leakage.

−	However, due to the long “lag-time” (it can take up to 40 years before undesirable pollutants leach into the soil and enter the water supply), the Chalk has been subject to specialised engineering models that simulate how these toxic materials work their way into the groundwater. Modelling has influenced decisions to increase investment in in-situ aquifer treatment ~~as a solution in the Chalk region~~.	+	However, due to the long “lag-time” (it can take up to 40 years before undesirable pollutants leach into the soil and enter the water supply), the Chalk has been subject to specialised engineering models that simulate how these toxic materials work their way into the groundwater. Modelling has influenced decisions to increase investment in in-situ aquifer treatment.

	= The London Basin Chalk Aquifer management plan =		= The London Basin Chalk Aquifer management plan =

−	In August 2018, the Environment Agency ~~released a~~ status report on the management of the London Basin Chalk Aquifer. The reports, which began in the 1990s, ~~were meant to~~ document the rise in groundwater levels~~. They also outlined~~ a management plan to protect the aquifer as a sustainable, secure and high quality water resource while protecting ~~the~~ infrastructure from floods ~~and other structural damage~~.	+	In August 2018, the Environment Agency published the latest status report on the management of the London Basin Chalk Aquifer. The reports, which began in the 1990s, document the rise in groundwater levels and outline a management plan to protect the aquifer as a sustainable, secure and high-quality water resource while protecting infrastructure from floods.

−	The report found that reduced groundwater levels have eroded the natural groundwater outlet in the centre of the London Basin. This has resulted in the intrusion of saline river water from the tidal Thames and could lead to the release of sulphate-rich, acidic groundwater through pyrite oxidation. The impact of this ~~potential activity~~ requires additional research.	+	The 2018 report found that reduced groundwater levels have eroded the natural groundwater outlet in the centre of the London Basin. This has resulted in the intrusion of saline river water from the tidal Thames and could lead to the release of sulphate-rich, acidic groundwater through pyrite oxidation. The impact of this requires additional research.

−	~~The~~ group of experts assembled in 1992 to manage the London Basin. ~~Referred to as the~~ General Aquifer Research Development and Investigation Team (GARDIT)~~, the group implemented~~ a strategy ~~to arrest the rise in groundwater.~~	+	A group of experts were assembled in 1992 to manage the London Basin. The General Aquifer Research Development and Investigation Team (GARDIT) developed a strategy with five phases:
−		+
−	~~The GARDIT strategy was defined by Thames Water, the Environment Agency, London Underground, the Corporation of London, Envirologic, the Association of British Insurers (ABI) and BT.~~	+
−		+
−	~~The~~ five phases ~~were defined as follows~~:	+

	* Phase 1 - Thames Water to re-commission disused sources.		* Phase 1 - Thames Water to re-commission disused sources.
Line 51:		Line 47:
	* Phase 5 - Thames Water to create new borehole sites in outer area.		* Phase 5 - Thames Water to create new borehole sites in outer area.

−	The GARDIT strategy achieved its goal in 2000~~. However~~, ~~additional~~ data suggests ~~the~~ levels will require ~~the continuation of~~ artificial management ~~in order to maintain them~~.	+	The GARDIT strategy achieved its goal in 2000, however, subsequent data suggests levels will require continual artificial management.

	= Related articles on Designing Buildings Wiki =		= Related articles on Designing Buildings Wiki =