Date of Award

Spring 5-6-2022

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Quaternary and Climate Studies

Advisor

Daniel H. Sandweiss

Second Committee Member

Alice R. Kelley

Third Committee Member

Kirk A. Maasch

Additional Committee Members

Shaleen Jain

Abstract

Within coastal Andean archaeology there is a growing emphasis on the roles of hydrology and hydrological knowledge in Andean strategies for water management, settlement, and land use. Hydrological methods can not only help reconstruct past water environments but also illuminate the influence of changing climates and conditions in the Andean highlands on coastal water flows. Through a case study of the Supe River basin in north-central coastal Peru, focusing on the period from 5000 to 3000 calibrated radiocarbon years before present (cal. BP), I review several hydrological methods useful for archaeological study. I then combine these to develop a paleohydrological model that provides a basis for comparing the hydrological effects of changing climates, environmental factors, and settlement and land use patterns.

Recognizing the importance of Andean highland climates on coastal river flows, I begin by developing a paleoclimate synthesis for the Norte Chico region (i.e., the Fortaleza, Pativilca, Supe, and Huaura basins) from 6000 to 2000 cal. BP. There has been considerable paleoclimate research in both the highlands and the coast but only limited efforts to develop these records into a coherent narrative of basin-wide climate patterns. Through a review of 21 studies spanning the tropical Andes, the central Andean highlands, the Altiplano, and the Peruvian coast, I identify three millennial-scale periods defined by distinct climatic transitions affecting the highlands and/or the coast: 6000-4000 cal. BP, 4000-3200 cal. BP, and 3200-2000 cal. BP.

I then apply paleohydrological methods, which are largely grounded in geospatial analysis in a geographic information system. The first method is drainage network modeling from a digital elevation model, which defines stream networks and catchments for a study area. The second method is delineation of hydrological response units (HRUs), which are areas that have similar hydrological dynamics. The HRU model uses climate-based parameters derived from the paleoclimate synthesis to create a spatial layer of climate regions and combines these with geological and soils layers to define discrete units of shared characteristics. Although both methods provide useful context on their own, I combine them through a qualitative assessment of hydrological dynamics within and between each of the HRUs, tracing their effects on surface and ground water flows from the highest elevations through inland valleys to the coast. This is the core of the paleohydrological model.

The hydrological conditions suggested by the model provide a basis for considering how Supe Valley settlement patterns relate to intra-basin and temporal variations in water availability, access to water and irrigable land, and flood risk. The study period is characterized by intensified settlement and agriculture in the inland valleys of the Norte Chico region between 5000 and 4000 cal. BP followed by marked shifts in the fortunes of certain settlements with a long-term decline in activity. The analysis calls into question previous hypotheses regarding social organization in the Supe Valley, irrigation practices, and the contribution of environmental processes to the region’s decline and suggests directions for future research to clarify these developments.

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