## 2 Geographical Setting and Geophysical Environment Factors  
To better understand the knowledge advances from earlier studies, the paleo-engineering underlying the raised-field system's capabilities to preserve crops through periods of seasonal climate change is focused first on the geophysics and seasonal meteorological change effects active in the altiplano raised-field Pampa Koani farming area of c. 500-1100 CE Tiwanaku in Bolivia (Figure 1).  
Lake Titicaca is located at 16\({}^{\circ}\) south, 69\({}^{\circ}\) west, at ~3810 m above sea level on the Bolivian altiplano. The bedrock of the Titicaca basin is largely igneous basalts and andesites with sedimentary rocks, shales, sandstones and isolated pockets of limestones [33; 34]. The altiplano and Lake Titicaca were formed in the Miocene period with the rise of the Andes [35; 36; 37], which attained the present form in the Plio-Pleistocene period. The annual rainfall near Lake Titicaca averages 687 \(\pm\) 138 mm, which is concentrated in the December-March rainy season. The annual mean air temperature at the altiplano lake elevation is approximately ~9\({}^{\circ}\)C with an amplitude of \(\pm\)12 \({}^{\circ}\)C. For Andean weather systems, the diurnal temperature variation is greater than seasonal temperature variation. The mean temperature of Lake Titicaca surface water is ~11-15 \({}^{\circ}\)C. The average incident solar radiation is high at 520 calories/cm\({}^{2}\) day, with heat absorption into moist berm topsoil varying with seasonal wet and dry conditions; the presence of rainwater and moisture-laden clouds affects solar IR heat transfer to the ground surface. Lake Titicaca evaporative water losses amount to nearly all of the precipitation in the basin area, and only a small amount of water leaves Lake Titicaca through the adjoining Rio Desaguadero or through deep aquifer seepage [38].  
Over the past 100,000 years, Lake Titicaca has been as much as 100 m above its current level [37]. Some sedimentological studies indicate a lake-level fluctuation of +10 to \(-\)50 m for the past 12,000 years. In historical times, the lake level has fluctuated as much as ~5 m within a two-year period [26; 37; 38; 39; 40]. The last major fluctuation occurred between September 1985 and April 1986, when the level of the lake rose nearly 3 m in height from excessive rainfall, inundating many square kilometers of the littoral zone in Peru and Bolivia, destroying c. 11,000 ha of agricultural fields planted with potato and other crops. The cultivars of the altiplano in early occupation Tiwanaku times were characterized by an array of high-altitude adapted maize, potatoes, caniwa and other tubers, such as oca, mashua and alluco. These food crops were complemented by other specialty crops grown at lower altitudes acquired through trade with Tiwanaku satellite settlements [12; 13; 41; 42]. Together with carbohydrate- and protein-rich raised-field resources (particularly quinoa, potato and maize), lacustrine resources from nearby Lake Titicaca and forage grass crops at local and higher altitude pastranges supporting large camelid herds with protein and vital dietary minerals, the ~30,000 population of urban Tiwanaku assured its continuity and health from a balanced multi-source food supply during favorable climate times.