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As clean water becomes more difficult to acquire, the need for secure water containment and transport grows. This problem is exacerbated by urban water demands and increased agricultural production in remote areas around the world. There is a demand for vast amounts of water in areas where water does not naturally exist at the levels needed. To mitigate this problem, canals have been constructed to transport water from the source to where it is needed.

These canals need to be lined with impermeable material to reduce the loss of water due to seepage during conveyance in the canals. Traditionally, canals used to transport water to where it is needed were lined with concrete or compacted earth. While earthen canals are relatively inexpensive to build, they lose more than 50 percent of water due to seepage and also suffer from erosion and vegetative growth. On the other hand, although concrete canals are not plagued by erosion or plant life, they too have major disadvantages; they are more expensive than earthen canals, are prone to cracking over time, and still lose at least 30 percent of water to seepage.

Geosynthetics, either alone or in conjunction with a concrete veneer, can greatly increase the effectiveness of a canal lining system. Combination of various Geosynthetics materials in the form of geotextile, geogrids, geomembrane, and geonets are used in the lining of canals to perform the function of drainage, impermeability, filtration, etc. They help in minimizing the seepage losses, mitigate pore water pressure being built up beneath lining, and reduce waterlogging related problems.

The study indicates that seepage can be reduced from 50 percent or more for earthen canals to 10 percent for geomembrane lined canals and less than 5 percent for canals using geomembrane in conjunction with a concrete cover. Not only are erosion and vegetative intrusion mitigated, but leakage is greatly reduced as compared to a concrete alone system. While the concrete veneer may still crack over time, the geomembrane remains in place underneath the veneer to prevent seepage until the concrete can be repaired. In addition to geomembranes, geotextiles may be used underneath the geomembrane to cushion it from rocky or uneven subgrade. Geogrids may be used to support the lining system over poor subgrade.

Geomembranes have been used as water canal liners to control seepage since the 1950s and are an effective alternative to more traditional lining methods, such as concrete and compacted soil. The flexibility of geomembranes allows them to conform to the canal subgrade without puncturing and to adapt to subgrade changes with time. Geomembranes are also less pervious than concrete and compacted soil allowing for less loss of water over time. Geomembrane canal liners may be left exposed or may be protected with a concrete cover. Most geomembranes are UV stabilized and can remain exposed for an extended length of time with no decline in their level of performance. However, because exposed geomembranes are more susceptible to damage from such things as rocks, debris, equipment, animal intrusion, and vandalism, most geosynthetic lined canal systems should be protected with a concrete cover or, at minimum, an earthen cover for ballast. For such applications, the protective concrete covering may be cast-in-place with reinforcing steel, pumped into geotextile forms, pre-cast in panels, or spray applied. Geomembranes are well suited not only for new construction but also for lining over existing earthen or concrete canals that may be cracked and leaking.

Traditionally, PVC geomembranes have been the geomembrane used for canal-lining projects. However, recently polyethylene (PE) based geomembranes (HDPE, LDPE, CSPE, and VLDPE), as well as several other types of geomembranes (e.g. EDPM and polypropylene), have been used as canal liners.

High-density polyethylene (HDPE) geomembranes are the most commonly selected geosynthetic for water containment. For canal lining, HDPE is perhaps best specified for new installations in which one can be assured of proper grading and compaction of the earth. HDPE, while very strong, is susceptible to stress-cracking when placed under loads for which it is not intended. For example, differential settlement and uneven terrain can cause those strains to an installation. One might encounter these conditions more often with older canals. But with proper construction and installation practices, the HDPE geomembrane performs wonderfully and offers, additionally, excellent hydrocarbon, chemical, and abrasion resistance—the very reason it's become so popular across design segments.

Linear low-density polyethylene (LLDPE) geomembrane panels have greater flexibility than HDPE geomembranes so can forgive some differential settlement. LLDPE has a higher yield strain. Like HDPE, it offers excellent resistance to abrasion.

Ethylene propylene diene monomer (EPDM) is a highly flexible and stable synthetic rubber. EPDM can conform to the shape of the earth over which it is installed. This makes it attractive for new and old installations. Also, EPDM, being so flexible, can be manufactured in large panels that can be welded together in the factory. This can produce time and cost savings for installation.

Polyvinyl chloride (PVC) geomembranes have been specified as liners, including as buried liners, for seepage control of concrete and earthen canals on a wide level, as well as for irrigation reservoirs. PVC geomembranes are very flexible, like EPDM, and large panels of the material can be seamed together in the factory and shipped to the site, thereby making for a quick installation with strong confidence in the seams. Of note, the factory seaming of materials like PVC, EPDM, and flexible polypropylene (FPP) might mean they can be installed without dewatering a canal that's already in operation. 

Chlorosulphonated polyethylene (CSPE) geomembrane is another material that can be welded together in large panels in the factory. It uses chlorine and sulfur to soften the polyethylene structure to create this flexibility for seaming. The reinforcement makes it a very strong geomembrane with excellent UV exposure and long-term performance, but it has a lower elongation break; thus, it does not conform as well to rough subgrade.

Some companies produce composite geomembrane materials used in mining applications. An example would be a PVC or LLDPE geomembrane sandwiched between geotextiles. The geotextiles often provide increased resistance to puncture, tear propagation, and friction related to sliding.

The geosynthetics industry, during the last three decades, has developed a wide range of materials that are useful in the development of irrigation and drainage projects, especially for controlling seepage and erosion. Geosynthetics now provide unprecedented possibilities for the design and construction of low embankment dams, cost-effective solutions for slope and canal protection, and long-term solutions for control of seepage losses from reservoirs and canals. It is now possible to find a geosynthetic material that meets project specifications and has durability consistent with the project design life, even under extreme climatic conditions. Experience of application of geosynthetics in several countries has amply proved their superiority over the traditional hard/ rigid lining materials in respect of quality, saving in cost and time of installation, especially for irrigation canals in operatio