Concrete-lined earthen reservoir

Lined earthen reservoirs can be built in natural depressions, or constructed by excavating and building a dam around the reservoir. If possible, the quantities of excavation and refill are kept nearly identical, to minimize the amount of work. The inner and outer walls of such a reservoir are always sloped, and inlets and outlets are installed during the earthwork. The walls and bottom of the reservoir must be compacted, especially the parts made by refilling. The inside of the reservoir is waterproofed by a lining of concrete, which is usually poured on-site in large slabs. The slab size is limited by the ability of the concrete slab to support its own weight when it is moved into place during construction of the reservoir. Once in place, the slabs are connected by a sealing of waterproof material. More recently, reservoirs have been constructed using a single slab of concrete, using ferrocement technology. Linings can also be made of clay, loam or plastic.