The method
Before using the result
- Cylindrical internal casing dimensions. Stored water volume is not sustainable well yield.
Worked examples
These original training examples illustrate the method for NGWA Certified Well Driller (CWD) General Drilling Examination. Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Estimate water stored inside a cylindrical casing from actual internal dimensions. Distinguish the water column already present from the aquifer ability to replenish it.
- Actual internal diameter
- 50 mm
- Water-column height
- 20 m
- V = π × 0.05² × 20 / 4 = 0.039269908169872414 m³.
- Stored water: 0.03926991 m³
2. Comparison example
Compare a different supplied condition using the same method. For Well Contractor Exam, the important check is that the input meaning, units and method assumptions still match the problem.
- Actual internal diameter
- 50 mm
- Water-column height
- 30 m
- V = π × 0.05² × 30 / 4 = 0.05890486225480863 m³.
- Stored water: 0.05890486 m³
Check your understanding
1. Which relationship is used?
Stored water volume = πD²h/4.
2. Which assumption should you check first?
Cylindrical internal casing dimensions. Stored water volume is not sustainable well yield.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to NGWA Certified Well Driller (CWD) General Drilling Examination free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.