Assessing Groundwater Source Yield - Revision history

Beod at 07:45, 16 June 2020

2020-06-16T07:45:47Z

← Older revision		Revision as of 08:45, 16 June 2020
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	There are different ways of testing the yield of a borehole or well to assess how much it can sustainably provide, but they all involve measuring the maximum pumping rate that can be sustained for a reasonable drawdown of the water level (i.e., so that the water level stays above the pump intake).		There are different ways of testing the yield of a borehole or well to assess how much it can sustainably provide, but they all involve measuring the maximum pumping rate that can be sustained for a reasonable drawdown of the water level (i.e., so that the water level stays above the pump intake).

	The following gives a brief summary of testing borehole yield. More details on methods for testing borehole yield, which are particularly appropriate for rural water supply in an African context, can be found in the chapter ~~[https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007~~ '''Designing and Constructing Water Points'''] in [http://~~nora~~.~~nerc~~.ac.~~uk/501046~~/ MacDonald et al. (~~2001~~)], which can be freely downloaded online.		The following gives a brief summary of testing borehole yield. More details on methods for testing borehole yield, which are particularly appropriate for rural water supply in an African context, can be found in the chapter '''Designing and Constructing Water Points''' in [http://dx.doi.org/10.3362/9781780441290 MacDonald et al. (2005)], which can be freely downloaded online.

	An initial estimate of borehole yield can be made when the borehole is airlifted after drilling, but this is a very approximate method. It gives no information about water level drawdown in the borehole, and therefore no information about the sustainable yield. However, it can indicate whether a borehole is likely to be productive enough to be worthwhile installing screen and casing, and what size of pump to use for a pumping test.		An initial estimate of borehole yield can be made when the borehole is airlifted after drilling, but this is a very approximate method. It gives no information about water level drawdown in the borehole, and therefore no information about the sustainable yield. However, it can indicate whether a borehole is likely to be productive enough to be worthwhile installing screen and casing, and what size of pump to use for a pumping test.

	A short, simple pumping test that is suitable for a relatively low yielding borehole capable of supplying enough water for a hand pump for 250 people, is a bailer test. Water is removed from the borehole with a bailer of known volume for a short time – e.g. 10 minutes – and the water level is measured as it recovers, usually for about 30 to 60 minutes. The equipment needed is a 20 m rope; a stopwatch; a water level dipper; and one or preferably two simple bailers that will fit freely down the borehole. The results can be analysed using sound theoretical principles. The procedure for carrying out and analysing a bailer test is given in ~~[https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007~~ Designing and Constructing Water Points] in [http://~~nora~~.~~nerc~~.ac.~~uk/501046~~/ MacDonald et al. (~~2001~~)].		A short, simple pumping test that is suitable for a relatively low yielding borehole capable of supplying enough water for a hand pump for 250 people, is a bailer test. Water is removed from the borehole with a bailer of known volume for a short time – e.g. 10 minutes – and the water level is measured as it recovers, usually for about 30 to 60 minutes. The equipment needed is a 20 m rope; a stopwatch; a water level dipper; and one or preferably two simple bailers that will fit freely down the borehole. The results can be analysed using sound theoretical principles. The procedure for carrying out and analysing a bailer test is given in the chapter '''Designing and Constructing Water Points''' in [http://dx.doi.org/10.3362/9781780441290 MacDonald et al. (2005)].

	For higher yielding boreholes, a constant rate test using an electrical pump should be carried out. This involves pumping the borehole at a constant rate for a certain period – usually at least 3 hours – and measuring the change in water level in the borehole during pumping and after pumping stops, as the water level recovers. The test results are analysed to give information about aquifer transmissivity – a measure of how easily groundwater can flow through the aquifer. A constant rate test requires a water level dipper and stopwatch, and an electrical pump of suitable size to match the potential borehole yield. A procedure for carrying out and analysing a constant rate test is given in ~~[https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007~~ Designing and Constructing Water Points] in [http://~~nora~~.~~nerc~~.ac.~~uk/501046~~/ MacDonald et al. (~~2001~~)].		For higher yielding boreholes, a constant rate test using an electrical pump should be carried out. This involves pumping the borehole at a constant rate for a certain period – usually at least 3 hours – and measuring the change in water level in the borehole during pumping and after pumping stops, as the water level recovers. The test results are analysed to give information about aquifer transmissivity – a measure of how easily groundwater can flow through the aquifer. A constant rate test requires a water level dipper and stopwatch, and an electrical pump of suitable size to match the potential borehole yield. A procedure for carrying out and analysing a constant rate test is given in the chapter '''Designing and Constructing Water Points''' in [http://dx.doi.org/10.3362/9781780441290 MacDonald et al. (2005)].

Beod at 10:38, 2 July 2019

2019-07-02T10:38:41Z

← Older revision		Revision as of 11:38, 2 July 2019
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

			Please cite page as: Africa Groundwater Atlas. 2019. Assessing Groundwater Source Yield. British Geological Survey. Accessed [date you accessed the information]. ''Weblink''.

	This page is still in development - please check back soon for updates.		This page is still in development - please check back soon for updates.
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	Return to: [[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]]		Return to: [[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

Beod at 12:28, 6 March 2019

2019-03-06T12:28:57Z

← Older revision		Revision as of 13:28, 6 March 2019
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] ~~>> Assessing Groundwater Source Yield~~		Return to: [[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]]

Beod at 14:51, 9 January 2019

2019-01-09T14:51:38Z

← Older revision		Revision as of 15:51, 9 January 2019
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

	This page is still in development - please check back soon for updates.		This page is still in development - please check back soon for updates.
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Developing groundwater resources \| Developing groundwater resources]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

Beod at 17:06, 8 January 2019

2019-01-08T17:06:57Z

← Older revision		Revision as of 18:06, 8 January 2019
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	An initial estimate of borehole yield can be made when the borehole is airlifted after drilling, but this is a very approximate method. It gives no information about water level drawdown in the borehole, and therefore no information about the sustainable yield. However, it can indicate whether a borehole is likely to be productive enough to be worthwhile installing screen and casing, and what size of pump to use for a pumping test.		An initial estimate of borehole yield can be made when the borehole is airlifted after drilling, but this is a very approximate method. It gives no information about water level drawdown in the borehole, and therefore no information about the sustainable yield. However, it can indicate whether a borehole is likely to be productive enough to be worthwhile installing screen and casing, and what size of pump to use for a pumping test.

	A short, simple pumping test that is suitable for a relatively low yielding borehole capable of supplying enough water for a hand pump for 250 people, is a bailer test. Water is removed from the borehole with a bailer of known volume for a short time – e.g. 10 minutes – and the water level is measured as it recovers, usually for about 30 to 60 minutes. The equipment needed is a 20 m rope; a stopwatch; a water level dipper; and one or preferably two simple bailers that will fit freely down the borehole. The results can be analysed using sound theoretical principles. The procedure for carrying out and analysing a bailer test is given in [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 ~~'''~~Designing and Constructing Water Points~~'''~~] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)].		A short, simple pumping test that is suitable for a relatively low yielding borehole capable of supplying enough water for a hand pump for 250 people, is a bailer test. Water is removed from the borehole with a bailer of known volume for a short time – e.g. 10 minutes – and the water level is measured as it recovers, usually for about 30 to 60 minutes. The equipment needed is a 20 m rope; a stopwatch; a water level dipper; and one or preferably two simple bailers that will fit freely down the borehole. The results can be analysed using sound theoretical principles. The procedure for carrying out and analysing a bailer test is given in [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 Designing and Constructing Water Points] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)].

	For higher yielding boreholes, a constant rate test using an electrical pump should be carried out. This involves pumping the borehole at a constant rate for a certain period – usually at least 3 hours – and measuring the change in water level in the borehole during pumping and after pumping stops, as the water level recovers. The test results are analysed to give information about aquifer transmissivity – a measure of how easily groundwater can flow through the aquifer. A constant rate test requires a water level dipper and stopwatch, and an electrical pump of suitable size to match the potential borehole yield. A procedure for carrying out and analysing a constant rate test is given in [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 ~~'''~~Designing and Constructing Water Points~~'''~~] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)].		For higher yielding boreholes, a constant rate test using an electrical pump should be carried out. This involves pumping the borehole at a constant rate for a certain period – usually at least 3 hours – and measuring the change in water level in the borehole during pumping and after pumping stops, as the water level recovers. The test results are analysed to give information about aquifer transmissivity – a measure of how easily groundwater can flow through the aquifer. A constant rate test requires a water level dipper and stopwatch, and an electrical pump of suitable size to match the potential borehole yield. A procedure for carrying out and analysing a constant rate test is given in [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 Designing and Constructing Water Points] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)].

Beod at 16:55, 8 January 2019

2019-01-08T16:55:22Z

← Older revision		Revision as of 17:55, 8 January 2019
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater ~~Development Techniques~~ \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

	This page is still in development - please check back soon for updates.		This page is still in development - please check back soon for updates.
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater ~~Development Techniques~~ \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater development techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

Beod at 16:54, 8 January 2019

2019-01-08T16:54:31Z

← Older revision		Revision as of 17:54, 8 January 2019
Line 1:		Line 1:
	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> Groundwater Development Procedures >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater Development Techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

	This page is still in development - please check back soon for updates.		This page is still in development - please check back soon for updates.
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	[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> Groundwater Development Procedures >> Assessing Groundwater Source Yield		[[Africa Groundwater Atlas Home \| Africa Groundwater Atlas]] >> [[Additional resources \| Resource pages]] >> [[Groundwater Development Techniques \| Groundwater Development Procedures]] >> Assessing Groundwater Source Yield

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2019-01-08T16:51:40Z

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[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Resource pages]] >> Groundwater Development Procedures >> Assessing Groundwater Source Yield

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==Testing Borehole or Well Yield==

There are different ways of testing the yield of a borehole or well to assess how much it can sustainably provide, but they all involve measuring the maximum pumping rate that can be sustained for a reasonable drawdown of the water level (i.e., so that the water level stays above the pump intake).

The following gives a brief summary of testing borehole yield. More details on methods for testing borehole yield, which are particularly appropriate for rural water supply in an African context, can be found in the chapter [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 '''Designing and Constructing Water Points'''] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)], which can be freely downloaded online.

An initial estimate of borehole yield can be made when the borehole is airlifted after drilling, but this is a very approximate method. It gives no information about water level drawdown in the borehole, and therefore no information about the sustainable yield. However, it can indicate whether a borehole is likely to be productive enough to be worthwhile installing screen and casing, and what size of pump to use for a pumping test.

A short, simple pumping test that is suitable for a relatively low yielding borehole capable of supplying enough water for a hand pump for 250 people, is a bailer test. Water is removed from the borehole with a bailer of known volume for a short time – e.g. 10 minutes – and the water level is measured as it recovers, usually for about 30 to 60 minutes. The equipment needed is a 20 m rope; a stopwatch; a water level dipper; and one or preferably two simple bailers that will fit freely down the borehole. The results can be analysed using sound theoretical principles. The procedure for carrying out and analysing a bailer test is given in [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 '''Designing and Constructing Water Points'''] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)].

For higher yielding boreholes, a constant rate test using an electrical pump should be carried out. This involves pumping the borehole at a constant rate for a certain period – usually at least 3 hours – and measuring the change in water level in the borehole during pumping and after pumping stops, as the water level recovers. The test results are analysed to give information about aquifer transmissivity – a measure of how easily groundwater can flow through the aquifer. A constant rate test requires a water level dipper and stopwatch, and an electrical pump of suitable size to match the potential borehole yield. A procedure for carrying out and analysing a constant rate test is given in [https://www.developmentbookshelf.com/doi/abs/10.3362/9781780441290.007 '''Designing and Constructing Water Points'''] in [http://nora.nerc.ac.uk/501046/ MacDonald et al. (2001)].

[[Africa Groundwater Atlas Home | Africa Groundwater Atlas]] >> [[Additional resources | Resource pages]] >> Groundwater Development Procedures >> Assessing Groundwater Source Yield

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