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Located in the Department of Arequipa of southwestern Peru, the Colca River Valley has been transformed by agricultural terracing more than perhaps any other valley in the Andean region. Approximately 11,000-13,000 hectares of terraces cover virtually every surface of the valley, from the irrigated terrace complexes in the river gorge and surrounding valley sides, to the unirrigated, segmented terraces (now abandoned) that extend to just over 4000 meters above sea level (masl). By late prehispanic and early colonial times, it appears that the complex production and settlement system of the central part of the valley constituted the nucleus of a major regional chieftaincy: the Collaguas.

Extant studies of the area have focused mainly on dating and understanding the processes of construction, use, and abandonment of the valley's extensive terrace and hydraulic systems during the prehispanic and colonial periods, and have produced a complex view of the prehistory of the valley's agricultural systems that do not follow a linear development. However, a preliminary consensus has emerged which characterizes the history of the valley's productive systems in terms of perhaps four major transformations (see e.g. Denevan 1986, 1988; Malpass 1987; Malpass and de la Vera 1990; Treacy 1989):

1. The initial construction and use of segmented, non-irrigated terraces along the upper margins of the valley (ca. 3600-4000 masl), preliminarily dated to the Middle Horizon Period (ca AD 600-1000).

2. The abandonment of these upper terraces and the construction of platform and valley-side bench terraces and their associated hydraulic systems in the lower portions of the valley, dated preliminarily to the terminal Middle Horizon or the beginning of the Late Intermediate Period (ca. AD 1000-1460),
3. The possible intensification of production and expansion of platform terraces through an Inka imperial influence and/or presence during the Late Horizon period (ca AD 1460-1532), and
4. The "destructuration" during the colonial period of the diversified Collagua "vertical archipelago" centered in the central portion of the Colca Valley during late prehispanic times, including the eventual abandonment of some 60% of the massive complexes of irrigated bench terraces in the upper margins of the valley.

Although a number of causal factors are suspected to have acted in conjunction (Denevan 1987), the hypotheses of previous research have focused mainly on climatic perturbations and technological/infrastructural innovation. Very little is known regarding how the production system of the Collaguas changed in relation to long-term demographic and sociopolitical dynamics in and around the valley. In order to understand these important relationships, basic data are needed regarding archaeological site types, sizes, and spatial distributions through time, as well as a heuristic framework for comparing archaeological data with the information available in the detailed sixteenth and seventeenth century censuses (visitas) to the valley. Accordingly, this dissertation research project, financed by the Wenner-Gren Foundation for Anthropological Research, is directed toward achieving the following primary objectives:

Through the primary methodology of full-coverage survey, the project therefore seeks to evaluate the major transformations preliminarily identified throughout the prehistory of the valley, and to clarify the relationships between these (and/or others identified) changes to changes in demographic, sociopolitical, and "eco-logistical" organization by evaluating the following primary research questions: