Due to the large size and amount of building material need to construct these dams, the arch dam was invented. An arch dam is dependent on its shape for strength, requires less material to build, and is relatively thin. The first known arch dam is Kebar, which was built around 1280 AD in the Mongol period. The limestone dam is located near the ancient town of Quam and stands 85 ft high, 180 ft long at the crest, 16 ft thick at the crest and has a constant radius of curvature of 125 ft. An arch dam needs to be supported by the surrounding geology, the rock formations on either side support the arch.
In the seventeenth century Spanish dam building was superior to all other civilizations. A Spaniard named Don Pedro Bernardo Villarreal de Berriz wrote the first book on designing dams in 1736. In Don Pedro's time only two types of dams were built, arch dams for narrow gaps where the foundations had good solid rocks or gravity dams where the site was wide and shallow. Don Pedro's book suggested how to design dams properly and introduced new ideas such as a multiple arch dam. Don Pedro suggested that multiple arch dams would need artificial supports or buttresses to support the arches. This theory indirectly led to the invention of the buttress dam.
The buttress dam uses a series of cantilevers, slabs, arches or domes to support the face of the dam from the force of the water. Almendralejo dam is one of the earliest examples of a large buttress dam and is able to store water hydropower. Meer Allum dam is the earliest know examples of a true buttress dam of the multiple arch type.
The Spanish brought the art of dam building from Spain to the Americas. The idea of buttress dams was current in Spain, so many small buttress dams were used for irrigation purposes. In California, the Jesuit fathers established missions along the coastal regions. The Old Mission Dam built across the San Diego river in 1770 was one of the first dams in California. The dam was only 5ft tall and made of masonry and mortar. Soon modern multiple arch dams were built with concrete and rock filled dams was formed from dumped rock. A rock filled dam uses the large stone for stability and is filled with an impervious water face membrane and core wall. In 1884 the arch Bear Valley dam was built of masonry and morter but replaced with a concrete multiple arch dam in 1910. The large increase in dam building did not come until 1849 when the gold rush lead to a large increase in water demand.