Calculator Inputs
Flow Comparison Graph
Example Data Table
| Project | Area (m²) | Drawdown (m) | Permeability (m/h) | Flow Path (m) | Safety Factor | Estimated Flow (m³/h) |
|---|---|---|---|---|---|---|
| Basement Excavation A | 180 | 2.5 | 0.45 | 16 | 1.15 | 14.55 |
| Utility Trench B | 120 | 1.8 | 0.30 | 12 | 1.20 | 6.48 |
| Foundation Pit C | 250 | 3.0 | 0.60 | 18 | 1.20 | 30.00 |
| Road Crossing D | 320 | 2.2 | 0.52 | 20 | 1.25 | 22.88 |
Formula Used
Base formula: Q = k × A × i × SF
Where Q is flow rate, k is soil permeability, A is seepage area, i is hydraulic gradient, and SF is safety factor.
Hydraulic gradient: i = Drawdown / Flow Path Length
Adjusted flow: Adjusted Q = Base Q / Pump Efficiency
This simplified approach supports preliminary planning. Final dewatering design should also review stratigraphy, well losses, recharge, and boundary conditions.
How to Use This Calculator
- Enter the excavation area requiring groundwater control.
- Input the target drawdown below existing groundwater level.
- Provide soil permeability from testing or design assumptions.
- Enter the estimated flow path or influence length.
- Add a safety factor for uncertainty and field variation.
- Enter pump efficiency and daily operating hours.
- Set the planned number of pumps and optional spacing.
- Click calculate to view flow, pump demand, and chart results.
- Use CSV or PDF export for reporting and review.
FAQs
1. What does this dewatering flow calculator estimate?
It estimates groundwater inflow, adjusted pumping demand, daily discharge volume, and per-pump flow. It helps with early excavation planning and drainage sizing.
2. Is this calculator suitable for final engineering design?
No. It supports preliminary assessment only. Final design should include geotechnical data, pumping tests, well design, aquifer boundaries, and construction staging.
3. What unit should I use for soil permeability?
Use meters per hour in this version. Keep all inputs consistent with metric units to avoid incorrect flow estimates.
4. Why is pump efficiency included?
Pump efficiency adjusts theoretical flow to a more realistic pumping demand. Lower efficiency increases required pump capacity.
5. What is hydraulic gradient in dewatering?
Hydraulic gradient is the ratio between drawdown and the flow path length. It indicates the driving force for seepage toward wells or sumps.
6. How is recommended well count estimated?
The calculator gives a rough spacing-based estimate. It is only a planning indicator, not a substitute for professional well layout design.
7. Can I use this for sump pumping projects?
Yes, for early estimation. However, sump performance depends on trench layout, inflow concentration, sediment control, and excavation geometry.
8. What should I do after getting the result?
Compare the estimated flow with available pumps, review site risks, confirm assumptions with field data, and refine the design before construction starts.