Calculator Inputs
Performance Graph
Example Data Table
| Parameter | Example Value | Unit | Notes |
|---|---|---|---|
| Static Water Level | 15 | m | Measured before pumping starts. |
| Pumping Water Level | 28 | m | Water level during stable pumping. |
| Recovered Water Level | 18 | m | Level after recovery period. |
| Discharge Rate | 18 | m³/h | Observed field discharge. |
| Pumping Time | 6 | h | Total test pumping duration. |
| Allowable Drawdown | 10 | m | Design operating limit. |
| Safety Factor | 0.80 | - | Used to keep estimates conservative. |
| Late-Time Pair | t1=1, s1=2.2, t2=10, s2=4.1 | h, m | Used for transmissivity estimation. |
Formula Used
Drawdown, s = Pumping Water Level − Static Water Level
Specific Capacity = Discharge Rate / Drawdown
Capacity Yield = Specific Capacity × Allowable Drawdown × Safety Factor
Recovery % = ((Drawdown − Residual Drawdown) / Drawdown) × 100
Recovery Yield = Discharge Rate × Recovery Factor × Safety Factor
Slope per log cycle, Δs = (s2 − s1) / log10(t2 / t1)
T = (2.3 × Qday) / (4π × Δs)
The calculator reports a recommended well yield as the minimum of the test discharge rate, the capacity-based yield, and the recovery-based yield. This keeps the final estimate more conservative for design screening.
How to Use This Calculator
- Enter the static, pumping, and recovered water levels using the same depth reference.
- Enter the measured discharge rate and the pumping and recovery test durations.
- Add the well diameter, saturated thickness, allowable drawdown, safety factor, and operating hours.
- Provide two late-time drawdown readings for transmissivity estimation.
- Click Calculate Well Yield to display results above the form.
- Review the graph and result table before exporting CSV or PDF.
- Use the recommended yield for planning, then confirm with a full hydrogeologic assessment.
8 FAQs
1. What does well yield mean?
Well yield is the flow rate a well can produce under pumping conditions without causing unacceptable drawdown, poor recovery, or unstable long-term operation.
2. Why is drawdown important?
Drawdown shows how strongly the aquifer and well respond to pumping. Larger drawdown at the same discharge usually means lower efficiency or lower sustainable production.
3. What is specific capacity?
Specific capacity is discharge divided by drawdown. It helps compare well performance and is often used for quick screening of likely operating yield.
4. Why does the calculator use a safety factor?
A safety factor reduces estimated yield so design decisions stay conservative. It accounts for seasonal variation, aging, fouling, and field uncertainty.
5. What does recovery percent tell me?
Recovery percent indicates how much of the pumping drawdown disappears after pumping stops. Better recovery usually suggests stronger aquifer support or lower stress.
6. Is transmissivity the same as yield?
No. Transmissivity measures how easily water moves through the aquifer. Yield is the practical pumping rate the well can sustain under project limits.
7. Can I use this for final design?
This tool is suitable for screening and preliminary analysis. Final design should consider full pumping tests, site geology, well construction, and regulatory requirements.
8. Why is the recommended yield lower than discharge?
The calculator intentionally caps the recommendation using recovery and allowable drawdown checks. That approach helps avoid overestimating long-term field performance.