Canal Seepage Loss & Water That Never Arrives
Measures seepage
Enter the wetted dimensions, length, flow and seepage rate to get the wetted perimeter, the seepage per day, the flow per day and the loss percentage.
Measure your canal losses
Next: lining this 1,000 m reach can recover most of the 145 m³/day — about 1.7% of the 8,640 m³/day you push down it.
Seepage = wetted perimeter × length × rate. The wetted perimeter WP = b + 2·y·√(1+z²); seepage rate depends heavily on soil — sandy beds lose far more than clay or lined canals.
Canal seepage — key facts
- Loss
- Wetted perimeter × length × rate
- Biggest loss
- Seepage in unlined canals
- High loss %
- Low conveyance efficiency
- Cut it with
- Brick / concrete / HDPE lining
- Or
- Compaction & sealing
- Longer canal
- More wetted area, more loss
- Lining saves
- ≈ 70–90% of seepage
- Privacy
- Runs in your browser; nothing uploaded
Where the canal water disappears
Unlined earthen canals lose a lot of water by seepage through the wetted bed and sides — often the largest single loss between the water source and the field. The physics is simple: loss equals the wetted perimeter times the canal length times the seepage rate. A wide, leaky channel running for kilometres over sandy soil can give away a striking share of its flow before a drop ever reaches a crop.
This tool computes the wetted perimeter, the seepage volume per day, the flow per day and the loss percentage, so you can see exactly how efficient your channel is. Lining with brick, concrete or HDPE — or compacting and sealing the soil — cuts seepage sharply; a high loss percentage means low conveyance efficiency. Pair it with the Channel Flow and Pipe Size tools to design a delivery system that keeps the water moving.
See the real loss
Daily seepage volume from your own dimensions.
Judge efficiency
Loss percentage tells you how leaky it is.
Value the lining
Compare lined and unlined seepage rates.
Plan the delivery
Decide between open channel and pipe.
Frequently Asked Questions
What is canal seepage?+
Seepage is the water that soaks out of a canal through its wetted bed and sides into the surrounding soil as the water flows. In unlined earthen canals it can be the single biggest loss between the source and the field — water that is pumped or released but never reaches a crop, lowering the overall efficiency of the irrigation system.
How is seepage loss calculated?+
Loss = wetted perimeter × length × seepage rate. The wetted perimeter is the length of bed and sides that the water actually touches in cross-section, the length is how far the canal runs, and the seepage rate is the depth of water that soaks away per unit area per day. Multiply them to get the volume lost per day.
What is the wetted perimeter?+
It is the part of the canal's cross-section in contact with water — the bottom plus the two wetted side slopes — for a given flow depth. Seepage happens across this whole surface, so a wide, shallow channel with a large wetted perimeter loses more than a deep, narrow one carrying the same flow.
What is a typical seepage rate?+
Seepage rate depends on soil and lining. Coarse sand and gravel beds can lose well over 0.3 m³ per m² per day, loams much less, and a good concrete or HDPE lining only a small fraction of that. Local soil tests give the best value; the tool lets you enter the rate that matches your channel.
What is conveyance efficiency?+
Conveyance efficiency is the share of water entering the canal that actually reaches the field — the rest is lost mostly to seepage and some evaporation. A high loss percentage means low conveyance efficiency, so more water must be released at the head to deliver the same amount to the crop.
How much does lining save?+
Lining with brick, concrete or HDPE — or compacting and sealing the soil — cuts the seepage rate sharply, often by 70–90%. Enter the lined seepage rate to compare against the unlined channel and see the daily water saved; that saving is what justifies the lining cost over the system's life.
Why does loss percentage matter more than volume?+
The loss percentage compares the seepage to the flow being carried, so it tells you how efficient the channel is regardless of size. A large canal can lose a big volume yet still be efficient, while a small leaky channel may lose a huge share of its flow. Aim to bring the percentage down.
Does a longer canal always lose more?+
Yes, all else equal — seepage scales with the wetted area, which grows with length. That is why long earthen feeder canals are prime candidates for lining, and why delivering water in pipes over long distances often beats open channels where seepage soils and distances are large.
Does evaporation matter too?+
Evaporation also removes canal water, but in most earthen channels seepage dominates the loss by a wide margin. This tool focuses on seepage because that is where lining and compaction make the biggest difference; add a small allowance for evaporation in hot, slow-moving canals.
Are the results exact?+
They are a sound planning estimate. Real seepage varies with soil moisture, water depth, flow and the canal's condition, and it falls as the bed silts up over a season. Use field-measured seepage rates where you can, and treat the output as a basis for comparing lining options and sizing losses.