8.1 Geotextile materials for reservoir lining

TABLE 8.1 Geotextile materials for reservoir lining

TYPE OF LINER CHARACTERISTICS

RPE Thinner material compared with EPDM and PVC Lightest material Does not stretch but is rather flexible

Requires more time to apply over complex shapes More puncture resistant than PVC and EPDM Can last up to 40 years Fish and plant safe Can be welded with heat

EPDM Made of rubber

Stretches and folds well around corners

Requires an underlayer Sheets cannot be joined with simple heat guns Heaviest material; higher shipping cost Least puncture resistant Fish-safe material

PVC Heavier than RPE but lighter than EPDM Less puncture resistant than RPE but more resistant than EPDM

PVC sheets are often treated with chemicals toxic to fish

Inexpensive Easily degraded by direct UV light exposure PVC sheets are easily welded together

Sources: BTL Liners - Geomembrane Systems, n.d., “What’s the Best Material for Pond Liners: A Side-by-Side Comparison,” https://www.btlliners.com/best-material-for-pond-liners/, retrieved January 26, 2021; Pond Informer, June 18, 2019, “Comparison of Different Pond Liner Materials (Which Is Best?),” https://pondinformer.com/pond-liner-material-guide/. Note: EPDM = ethylene polypropylene diene monomer; PVC = polyvinyl chloride; RPE = reinforced polyethylene; UV = ultraviolet.

Reducing the risk of sedimentation

The lifetime of a borrow pit converted into a water-storage pond may be shortened if it is regularly filled with sediment-rich water flows. several measures are recommended to prolong its life:

• Locate borrow pits in areas with protected watersheds and low silt content in the runoff that feeds the borrow pits. This approach may not always be possible, but the health of the catchment may be a consideration in siting the borrow pit. • If well-protected watersheds are unavailable, use vegetation plantings to mitigate silting from the most critical sediment runoff areas. • Take steps to trap sediments before they reach the converted borrow pits.

Install sediment traps or employ vegetative measures. • Maintain sediment traps and vegetative measures that can fill up quickly. The sand in the sediment traps can sometimes be repurposed for use as building material or agricultural soil and may be harvested and sold.