How to Use This Calculator
Select a calculation method and measurement units. Enter the canal geometry and operating details. Review warnings before applying results to final engineering decisions.
- Choose field measurement, seepage flux, conductivity, empirical, percentage, or ponding.
- Describe the canal shape, dimensions, length, and hydraulic conditions.
- Apply soil, lining, uncertainty, and rehabilitation scenario factors.
- Add separate reaches when the canal changes along its route.
- Calculate, inspect assumptions, then export the complete result summary.
Formula Used
The calculator applies the selected method after unit conversion. Geometry determines flow area and wetted surface. Lining factors then adjust the estimated final seepage loss.
| Method | Core relationship | Main use |
|---|---|---|
| Inflow–outflow | Qₛ = adjusted inflow − adjusted outflow | Field discharge measurements |
| Flux | Qₛ = qₛPL | Known seepage rate per wetted area |
| Hydraulic conductivity | Qₛ = KiPL | Darcy-based screening estimate |
| Percentage | Qₛ = Qin × percentage | Rapid planning estimate |
| Ponding | Qₛ = corrected level drop × surface area ÷ time | Isolated reach test |
Example Data
This example represents an unlined trapezoidal irrigation canal. Values demonstrate the water-balance method only. Replace every example value with measured project information carefully.
| Input | Example value | Purpose |
|---|---|---|
| Bottom width | 3 m | Canal geometry |
| Water depth | 1.2 m | Area and perimeter |
| Side slopes | 1.5H:1V | Trapezoidal geometry |
| Reach length | 1,000 m | Wetted surface |
| Upstream flow | 2.5 m³/s | Incoming water |
| Downstream flow | 2.2 m³/s | Delivered water |
| Withdrawal | 0.1 m³/s | Known diversion |
| Evaporation loss | 0.01 m³/s | Non-seepage correction |
Frequently Asked Questions
What is canal seepage loss?
It is water moving through the canal bed or sides. The loss reduces delivered discharge downstream. Field measurements improve confidence in each reported seepage estimate.
Which method is most reliable?
Direct field measurements are usually preferred when conditions permit. Inflow–outflow needs accurate discharge and withdrawal records. Ponding tests suit carefully isolated reaches with stable water.
Why correct for evaporation?
Evaporation is not seepage through canal materials. Ignoring it can overstate subsurface losses. Rainfall and storage changes also require separate measured corrections.
What does the lining factor mean?
It multiplies the raw seepage estimate. A factor below one represents reduced leakage. Local seepage tests should support each selected correction factor.
Can empirical formulas replace field testing?
They provide screening estimates for similar regional conditions. Results can vary greatly outside calibration areas. Confirm major investments using reliable local field measurements first.
How is conveyance efficiency calculated?
The calculator compares remaining water against adjusted inflow. Known diversions and losses affect the result. Review all flow-balance entries and measurement timings very carefully.
What is seepage per wetted area?
It divides seepage discharge by submerged canal surface area. The result supports comparisons between different reaches. Results also appear as equivalent millimetres of loss daily.
Can I analyse several canal reaches?
Yes, add rows in the multiple-reach table. Each row accepts length, flux, flows, and factors. Results show both individual and combined reach seepage losses.
How does the cost comparison work?
It values annual saved water using pounds per cubic metre. The calculator estimates payback and discounted benefits. Future maintenance costs are not included within calculations automatically.
Why is an uncertainty range included?
Soil and lining properties vary across real canals. Multipliers show plausible lower and upper outcomes. Use wider ranges whenever supporting field evidence remains limited.
Is this suitable for final design?
It supports planning, checking, and preliminary engineering calculations. Final design needs calibrated data and professional review. Verify every formula against governing local standards before approval.