Canal & Irrigation Liner: Selection & Installation

Lined canals deliver 10–20% more water to the field than unlined earth channels — no seepage, no weed growth, faster flow. This guide covers HDPE liner selection and the installation sequence that keeps a canal watertight along its full length.

1Thickness Selection

2Subgrade Preparation

• Excavate the canal to a clean trapezoidal section; remove roots, rocks and sharp debris.
• Compact the bed and banks; fill soft spots so the profile is true and stable.
• Typical side slope 1:1.5 to 1:2; steeper slopes need textured liner or mechanical anchoring.
• On coarse or stony subgrade, install a 200–300 g/m² geotextile cushion first.

3Laying Direction Matters

• For a canal, unroll panels along the canal axis (longitudinal) so most seams run with the flow, not across it.
• Transverse joints should be staggered — no four corners meeting at one point.
• Overlap ≥ 100 mm; where the water flows, the upstream panel overlaps the downstream panel so flow doesn't lift the seam edge.

4Welding

• Use a double-track hot wedge welder; trial-weld each day before production welds.
• Weld speed 2–3 m/min, temperature 380–420 °C adjusted to ambient conditions.
• Pressure-test every seam (0.2 MPa, 5 min, drop < 20%); repair with extrusion weld + patch and vacuum-test.

5Anchoring

• Anchor the liner at the top of each bank in a 300–500 mm deep anchor trench, backfilled and compacted.
• At check structures, culverts and gates, weld pipe boots / flanges to the liner — leakage concentrates at structures.
• Leave 100–200 mm slack per 10 m for temperature movement.

6Cover & Protection

• Cover the bank liner with 100–150 mm soil (or vegetation mat) to protect from UV and tools; keep the bed liner exposed for maintenance and cleaning.
• Where machinery crosses, lay a geotextile or thin concrete protection strip first.
• For high-velocity sections (drops, chutes), consider a shotcrete or concrete overlay on the liner.