Groundwater Management in the 300 bce-1100ce Pre-Columbian City of Tiwanaku (Bolivia)

The ancient (300 BCE-1100 CE) city of Tiwanaku, capital of a vast South American empire, has been the subject of research starting from early 20th century scholars and continuing to the present day [1-10]. The city, located at the southern edge of the Lake Titicaca Basin in the south-central portion of the South American Andes at an altitude of 3800-3900 masl incorporated an elite area bounded by an encompassing perimeter canal that supported temple complexes, palace architecture and a stepped-pyramid (the Akapana) designed to serve ceremonial functions and provide residential structures for Tiwanaku’s rulers. Outside this center lay a vast domain of urban housing structures. An intricate network of canals acting in conjunction with the perimeter canal performed several hydrological functions: rapid ground drainage during both wet and dry seasons to promote health advantages for the city’s 20,000 inhabitants; flood defense to preserve the ritual center and surrounding urban structures and, most importantly, height excursion control of the deep groundwater base underlying the site. This latter function prevented dry-out collapse of the deep aquifer underlying the city’s monumental center preserving its bearing strength and limiting subsidence of foundation soils underlying massive monumental structures within the perimeter canal’s boundary.