A water lagoon is an artificial hydraulic structure located outside the channel (to differentiate from dams) and total or partially closed by a retention dyke. Irrigation, surface water abstraction, storage and distribution are the main applications. The use of geomembranes for waterproofing of water lagoons is essential in all cases, even in natural impermeable lands since they all are fitted with piping, junction parts, spillways, etc.. and sealing is not guaranteed without the use of geomembranes. The geomembrane also always protects the soil from erosion, vegetation growth, fracturing on drying, etc.Â Solution based on Geomembrane is undoubtedly the best according to durability when the geomembrane is of good quality, moderate cost and high performance and efficiency result. Use of this waterproofing solution however requires a minimal geometric requirements of the inclination and height of slopes, minimum width of the upper way to be anchored, fulfillment of flatness and compaction of supporting land, drainage, etc..Â Geomembranes coloured, reinforced or not, are available and a large number of fittings and accessories for junctions works, pipes, etc.. and, in general, all those applications that present special requirements.