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Questions and Answers
Manual excavation using a pick and shovel is employed in the construction of driven wells.
Manual excavation using a pick and shovel is employed in the construction of driven wells.
False
Bored wells or augered well are suitable for formations with deep water tables.
Bored wells or augered well are suitable for formations with deep water tables.
False
The process of constructing a jetted well involves driving pipes into the ground through repetitive impact.
The process of constructing a jetted well involves driving pipes into the ground through repetitive impact.
False
Driven wells are ideal for formations that have large gravel or rocks.
Driven wells are ideal for formations that have large gravel or rocks.
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The irrigation water requirement should be determined based on PNS/BAFS/PAES 217:2018.
The irrigation water requirement should be determined based on PNS/BAFS/PAES 217:2018.
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A site's slope should not be considered when determining its suitability for a well.
A site's slope should not be considered when determining its suitability for a well.
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A site should have high vulnerability to pollution and a high potential for seawater intrusion.
A site should have high vulnerability to pollution and a high potential for seawater intrusion.
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The depth of the water-bearing formation is not important when designing a well.
The depth of the water-bearing formation is not important when designing a well.
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The thickness of the aquifer affects the length of the screened or perforated section of the well.
The thickness of the aquifer affects the length of the screened or perforated section of the well.
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The presence of a hard confining layer doesn't affect well design or drilling methods.
The presence of a hard confining layer doesn't affect well design or drilling methods.
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Groundwater salinity is irrelevant when determining the suitability of water for irrigation.
Groundwater salinity is irrelevant when determining the suitability of water for irrigation.
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Hydraulic conductivity or transmissivity are important for determining the economic value of an aquifer as a water source.
Hydraulic conductivity or transmissivity are important for determining the economic value of an aquifer as a water source.
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The specific yield of an aquifer has no relation to well spacing.
The specific yield of an aquifer has no relation to well spacing.
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A pilot borehole should be reamed down to the lower 2 meters if the confining layer is soft.
A pilot borehole should be reamed down to the lower 2 meters if the confining layer is soft.
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When encountering resistance while lowering the pipe, turning the pipe with pipe wrenches can enhance its downward penetration.
When encountering resistance while lowering the pipe, turning the pipe with pipe wrenches can enhance its downward penetration.
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Turning the pipe during driving is recommended to ensure an air-tight connection between the pipe and the confining layer.
Turning the pipe during driving is recommended to ensure an air-tight connection between the pipe and the confining layer.
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Water jetting should be avoided when the perforated portion of the pipe is within the confining layer.
Water jetting should be avoided when the perforated portion of the pipe is within the confining layer.
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It is permissible to use cast couplings during driving to securely fasten the pipe sections.
It is permissible to use cast couplings during driving to securely fasten the pipe sections.
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Well development is done to decrease its discharge capacity and aid in continuous sand pumping.
Well development is done to decrease its discharge capacity and aid in continuous sand pumping.
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During jetting, the drilling stem may be equipped with a reduced jetting head to cause water surge within the well.
During jetting, the drilling stem may be equipped with a reduced jetting head to cause water surge within the well.
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Jetting should be started at the top of the well and proceed down to the bottom of the perforated pipe.
Jetting should be started at the top of the well and proceed down to the bottom of the perforated pipe.
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Schedule 40 GI pipe is recommended for naturally developed wells with a hard confining layer.
Schedule 40 GI pipe is recommended for naturally developed wells with a hard confining layer.
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For artificially developed wells, schedule 80 GI or PVC pipe is recommended.
For artificially developed wells, schedule 80 GI or PVC pipe is recommended.
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For aquifers thicker than 4.6 m, the extent of aquifer penetration should be 95% of the aquifer thickness.
For aquifers thicker than 4.6 m, the extent of aquifer penetration should be 95% of the aquifer thickness.
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For naturally developed wells with a design discharge of over 15 lps, the aquifer penetration will be between 50 percent and 100 percent.
For naturally developed wells with a design discharge of over 15 lps, the aquifer penetration will be between 50 percent and 100 percent.
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The total pipe length is calculated by adding the depth of the well, the length of the extension and the percentage of penetration.
The total pipe length is calculated by adding the depth of the well, the length of the extension and the percentage of penetration.
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For a single borehole, at least 1.4 meters should be added for the nipples for the installation of the pumping unit
For a single borehole, at least 1.4 meters should be added for the nipples for the installation of the pumping unit
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Slots in well pipes should be 5 to 8 mm in width and 40 to 70 mm in length.
Slots in well pipes should be 5 to 8 mm in width and 40 to 70 mm in length.
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The pipe bottom should be closed.
The pipe bottom should be closed.
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The full load continuous duty horsepower of a prime mover should be less than the pump brake horsepower.
The full load continuous duty horsepower of a prime mover should be less than the pump brake horsepower.
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An electric motor's body indicated power rating is estimated to be about 1.15 times the brake horsepower.
An electric motor's body indicated power rating is estimated to be about 1.15 times the brake horsepower.
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A water-cooled diesel engine has a higher body indicated power rating than an air-cooled diesel engine.
A water-cooled diesel engine has a higher body indicated power rating than an air-cooled diesel engine.
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A gasoline air-cooled prime mover has a body indicated power rating factor between 1.40 and 1.50.
A gasoline air-cooled prime mover has a body indicated power rating factor between 1.40 and 1.50.
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The recommended borehole size for well logging is 4 inches in diameter or smaller.
The recommended borehole size for well logging is 4 inches in diameter or smaller.
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Resistivity logging is a method used to determine the chemical characteristics of an aquifer.
Resistivity logging is a method used to determine the chemical characteristics of an aquifer.
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Spontaneous potential logging is a common method used for well logging according to the provided text.
Spontaneous potential logging is a common method used for well logging according to the provided text.
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Todd and Mays published a book called 'Engineering Hydrology'.
Todd and Mays published a book called 'Engineering Hydrology'.
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The effective size and uniformity coefficient of aquifer materials are determined through mechanical analysis like the sieve-hydrometer method.
The effective size and uniformity coefficient of aquifer materials are determined through mechanical analysis like the sieve-hydrometer method.
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A gravel pack with a thickness of at least 25 cm is recommended for aquifers having a uniformity coefficient less than 2.0 and an effective size less than 0.30 mm.
A gravel pack with a thickness of at least 25 cm is recommended for aquifers having a uniformity coefficient less than 2.0 and an effective size less than 0.30 mm.
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In aquifers with an effective size greater than 0.30 mm, a graded gravel pack is essential for filtration purposes.
In aquifers with an effective size greater than 0.30 mm, a graded gravel pack is essential for filtration purposes.
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For uniformly grained sand, the optimal gravel pack gradation should fall outside of two lines plotted using the 50% passing diameter multiplied by 5 and 10.
For uniformly grained sand, the optimal gravel pack gradation should fall outside of two lines plotted using the 50% passing diameter multiplied by 5 and 10.
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Well screen slot size should be greater than 1/2 of the 85% passing of the gravel pack materials.
Well screen slot size should be greater than 1/2 of the 85% passing of the gravel pack materials.
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For graded pack aquifer materials, the 50% passing size should be multiplied by 12 and 58 to determine plotting points for the gravel pack limits.
For graded pack aquifer materials, the 50% passing size should be multiplied by 12 and 58 to determine plotting points for the gravel pack limits.
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For graded pack materials, no gravel pack material should exceed a size of 20 mm.
For graded pack materials, no gravel pack material should exceed a size of 20 mm.
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A uniformly grained gravel envelope is recommended for aquifers with a UC of 2.5 and ES of 0.20 mm.
A uniformly grained gravel envelope is recommended for aquifers with a UC of 2.5 and ES of 0.20 mm.
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Study Notes
Philippine National Standard for Groundwater Irrigation - Shallow Tubewell
- This standard outlines procedures for shallow tubewell design, installation, and development using suction lift pumps.
- The standard was initiated by the Agricultural Machinery Testing and Evaluation Center (AMTEC) under a project focusing on nutrient and water use efficiency.
- The Bureau of Agriculture and Fisheries Standards (BAFS) is responsible for developing and endorsing standard specifications and test procedures for agricultural and fisheries machinery, as mandated by the Agricultural and Fisheries Mechanization Law of 2013.
- The standard adheres to BPS Directives Part 3:2003 regarding structure and drafting of international standards.
Scope
- The standard covers procedures for shallow tubewell design, installation, and development.
- The scope is limited to shallow tubewell capabilities using suction lift pumps.
References
- Normative documents referenced include PAES 127:2002 (Agricultural Machinery - Drilling Rig Specifications) and PNS/BAFS/PAES 217:2017 (Requirements for Determination of Irrigation Water).
Definitions
- Aquifer: A geologic formation containing water that transmits it at a sufficient rate for economical pumping.
- Confined aquifer: An aquifer confined or overlain by a relatively impermeable layer.
- Effective size: The particle diameter corresponding to a 10% sieve passing.
- Pumping test: Evaluation of aquifer properties by pumping water from a well and observing drawdown in observation wells.
- Shallow tubewell: A tube or shaft drilled to a depth typically less than 15 meters for shallow groundwater extraction using suction lift pumps.
- Unconfined aquifer: An aquifer with a water table as its upper surface.
- Uniformity coefficient: The ratio of the 60% passing size to the 10% passing size.
- Well log: A record documenting aquifer stratification, depth, thickness, lithology, and other characteristics.
Site Selection
- Site selection should ensure adequate yield based on aquifer transmissivity and specific yield, meeting irrigation water requirements.
- The site should have sufficient aquifer recharge or be located near suitable surface water sources.
- Water quality should meet national implementing agency standards for irrigation water.
- Sites should have low vulnerability to pollution and saltwater intrusion.
Well Characteristics
- Key aquifer properties and their importance in well design, drilling, and development, and in selecting pumping systems are outlined in Table 1.
- Well design, drilling, and development methods are further detailed.
- Methods used for well characterization and site investigation are detailed in Table 2, covering surface, remote sensing, and geophysical exploration, as well as electrical resistivity and seismic refraction methods, and test drilling for subsurface investigation.
Well Classification
- Various well types, including dug wells, bored wells, driven wells, and jetted wells, depending on the geological formation and water table depth are categorized and described.
- Details on materials and limitations for each type are given.
Discharge
- Section 7 outlines the procedure for determining the required pump discharge based on irrigation water requirements.
- Equations and calculations to determine the maximum sustained yield for confined and unconfined aquifers are given.
- Instructions for comparing and adjusting pump discharge to meet maximum sustained yield are included.
Shallow Tubewell Design, Installation, and Development
- Details on tubewell design, including pipe selection considerations, aquifer penetration, pipe perforation, drilling techniques, pipe installation, and well development procedures, are described.
Pump Selection
- Section 10 guides the selection of a pumping unit based on the required brake horsepower, total dynamic head, pump discharge, and efficiency.
- Tables outlining required power ratings for various prime movers (e.g., electric motors, diesel engines) are provided.
Well Logging Methods
- Appendix A describes well logging procedures to assess subsurface characteristics and evaluate aquifer properties, including sample collection and analysis.
- Provides guidance on using different methods and interpreting results.
Detailed Additional Info
- Specific details, like recommended pipe materials for different well types and aquifer characteristics, are included based on the provided documents.
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Description
Test your knowledge on various well construction methods such as manual excavation, bored wells, and jetted wells. This quiz covers important factors like site suitability, water table depth, and aquifer thickness that influence well design and irrigation water requirements. Prepare to delve into the nuances of groundwater management and its implications.
