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One River Project

Changes in Ancient Land and Water Use Along The Río Ica, Peru


LANDSAT of Río Ica, south coast Peru
LANDSAT of Río Ica, south coast Peru

The One River project, funded by the Leverhulme Trust and Don Alberto Benavides for a period of five years, and now in its first year of investigation, seeks to track the flux in rich cultural florescence and collapse through time along a single river — the Río Ica — from its headwaters in the southern Andes to its mouth on a desert coast.  The Andean region is one of humanity’s rare hearths of agriculture and ‘pristine’ civilisation. Its Pacific coast is one of the world’s driest deserts, whose only sources of water are rivers arising in its rain-fed highland hinterlands. Second only to the Himalayas, the Andes encompass tremendous variations in human ecology (Shimada 1985), and, at these tropical latitudes, support cultivation even to extreme altitudes.  Yet, despite the obvious interdependency between the hydrology and economy of coast and sierra, no investigation has yet taken the entire course of a single watershed as the appropriate unit of study within which to model changes in settlement, land use, water management and culture.  We propose to do so for the Río Ica over the deep-time perspective of archaeology, from the Early Horizon (c. 750 bc) through to the end of the Inca Empire (ad 1532), by combining archaeological survey and excavation with the latest GIS, geomorphological and archaeobotanical methodologies.

The Ica Valley is the perfect theatre within which to carry out such an investigation. Its ceramic sequence underlies Rowe’s (1967) widely used chronology for all Andean prehistory. The Río Ica links the highlands of Ayacucho with the south coast – two regions with long and rich cultural trajectories, not least those of the Wari Middle Horizon and Nasca, respectively. Here, the interactions between highlands and coast that characterise all Andean history, were — indeed still are — particularly intense. Today, significant stretches of the Río Ica on the coast and in the highlands are depopulated and bereft of cultivation. Yet their extensive archaeological remains attest to substantial ancient populations and thereby present a prima facie case for changing ecological and landscape conditions.

The climate along the Río Ica watershed varies from semi-arid (250.3 mm per year at Tambo, 3,250 m asl) to hyperarid (0.3 mm at Ocucaje, 320 m asl). The river’s flow is extremely seasonal and erratic, dropping through steep gradients in the sierra and then depositing rich alluvium in a series of wide basins on the coast.  In such dry lands, ecological thresholds are sharply defined. The division and management of water and land resources have therefore always been critical in moulding the social fabric of this region and have in turn been shaped by the fluctuating fortunes of politics and resource availability (Mayer 2002).


Research Objectives

Culture change in the ancient Andes has all too often been imputed to catastrophic climatic perturbations such as droughts and El Niño floods, according to a model of ‘punctuated equilibrium’ (Shimada et al. 1991; Moseley et al. 1981). While recognising their importance, we seek to develop our previous research, which distinguishes also the impacts of more gradual, human-induced change (Beresford-Jones et al. 2009 a, b, in press; French 2010a & b; Lane 2006, 2009).

We start by tracking the long-term shifts in settlement along the course of the Río Ica, from headwaters to mouth, as societies have mitigated, mediated and provoked environmental change through changing practices of land and water management.  For settlement dynamics are of course a reflex of the various political, social, economic and ecological factors that underlie the flowering, decline (or collapse), and regeneration of societies (Schwartz & Nichols 2006). We aim, thereby, to answer three research questions:

  1. How and when did settlement change along the drainage?
  2. How does that relate to changes in water and land management?
  3. Why did these changes occur?

The viability of this broad task is assured by the wide range of existing (if rather piecemeal) research already available for us to draw upon — our own included.  We shall now bring this together and supplement it by new, targeted studies on those areas for which few or no data yet exist, to produce an integrated model of settlement and land and water management along the entire course of the Río Ica.  The answers to our first two research questions, then, will unfold from testing the following hypotheses:

One River Riparian Oases
Riparian oases, Samaca Basin, lower Ica Valley, 250 m asl

a.   That vast, largely unexplored shell middens up to 150 m deep at the mouth of the Río Ica are the vestiges of the earliest settlement of semi-sedentary societies exploiting a rich marine resource, and date to the early Holocene (Engel 1957).

b.   That floodplain agriculture began on the coast during the early Ocucaje phases c. 750 bc, when settlement seems to have been concentrated in the lower Ica Valley (Massey 1991, Cook 1999).  Thereafter, interactions between highlands and coast intensified during the so-called Early Horizon.

c.   That settlement and irrigation agriculture expanded in the late Ocucaje (or ‘Paracas’) phases, and in due course evolved over the subsequent Early Intermediate Period (c. 0-500 ad) into the flourishing Early Nasca society (or societies) — any distinction between them being “essentially arbitrary” (Menzel et al. 1964: 2).

d.   That Late Nasca subsequently collapsed into internecine warfare. Settlements were dislocated and fewer. Canal systems were abandoned in the lower Ica Valley (Beresford-Jones et al. 2009b).  Hypotheses proposed to explain Nasca’s demise include:  El Niño/La Niña climatic perturbations (Silverman & Proulx 2002); underlying, gradual processes of human-induced deforestation exacerbating the former (Beresford-Jones et al. 2009a and b); and increasing aridity in the highlands (Eitel & Mächtle 2009).

e.   That critical also to Nasca’s ‘collapse’ is a political dimension. For it coincides with the recently revised time depth of the Middle Horizon (ad 550–1000), when the huge urban centre of Wari in the Ayacucho highlands rose to dominate the coast (Menzel 1967, Schreiber 1999). This Middle Horizon “apparently marks the virtual replacement of one culture by a radically different one on the south coast” (Rowe 1956: 148).

f.   That by around ad 1000 Wari itself, and thereby its influence on the Ica Valley, collapsed.  Hypotheses for why this occurred include climate change and environmental degradation in Wari’s own urban core (Isbell et al. 1991).  At this time too the lower Ica Valley was abandoned to significant settlement (Beresford-Jones 2009a).

g.   That in the highlands the subsequent Late Intermediate Period saw a fragmentation of power as acephalous societies engaged in more sophisticated systems of hydraulic management, underpinning a complex, mixed agro-pastoralist economy (Lane 2009). On the coast, meanwhile, new canal systems opened up, for the first time, the middle Ica Valley to agriculture and substantial occupation (Massey 1991). One of the centres of the Late Intermediate was Ica-Chincha, ultimately to become among the most powerful polities under the Inca Late Horizon (Menzel 1976; Rostworowski 1989).

h.   That the settlement patterns encountered by the Spanish when the City of Ica was founded in the middle Ica Valley in 1563 (Rossel Castro 1968), are, more or less, still those of today.  Yet the Spanish conquest brought population collapse of up to 94% by some estimates (Cook 1981), followed by resettlements (reducciones), especially in the highlands.  In due course, a rigid new social stratification emerged, reflected not least in the control of water resources.  This persisted for centuries in the middle Ica Valley, where the population remains concentrated today (Oré 2005). Only in recent decades has that social order fractured, partly as a consequence of increasing — and clearly unsustainable — borehole exploitation of deep fossil groundwater (The Guardian 2010).

Having established a platform of data to answer our first two research questions, we shall then be able to turn to the third and much more contentious one of why change occurred. In previous research we have adopted the perspective of historical ecology (Balée 1998) to show how various land use and water management strategies, adopted at different times by different societies in the lower Ica Valley, impacted upon the landscape.  We aim now to expand the scale of that analysis to produce a picture, integrated along the whole Río Ica drainage, for how watershed management and land-use have both shaped and been shaped by the florescence and decline of cultures through time.  As the above hypotheses suggest, naturally, this will include the impacts of climatic perturbations, but we expect it to go far beyond traditional models in requiring a much greater role also for human agency — in creating, managing, and sometimes provoking detrimental landscape change.


Significance of the Research
One River Ica Valley
Terraced upper Ica Valley near Santiago de Chocorvos, 3,000 m asl

This study of the Ica Valley will provide a concrete case-study charting how water management and land-use strategies have impacted upon human settlement and intra-site dynamics along the course of one river through prehistory and, indeed recorded times through to the present.  By taking — for the first time — an entire single watershed as its focus, it will provide a more nuanced study that does not just theorise on but describes how highland and lowland strategies of land use and water management were inter-related.  Regionally, the Río Ica case-study provides an excellent local proxy for understanding the changes in water management across the Andes.  More widely, it offers a framework by which to map the differences and relationships through time between human ecologies and social organisations in the highlands and on the coast.

Moreover, the answers to our archaeological research questions have powerful contemporary resonance. For today a new ‘Horizon’ is unfolding. The Ica coast has seen a population explosion through massive economic migration down from the Ayacucho highlands. The consequences of this are the abandonment of highland hydraulic systems, falling water tables on the coast and tremendous pressure upon fragile natural and agricultural biomes, all of which increase vulnerability to extreme climatic perturbations. By understanding similar processes in the past, we may hope to contribute to planning properly for the future.  Our case-study models water management as the reflex of human agency and concomitant political ecology over deep archaeological time-scales, through to the present day. Its relevance is obvious in a world where captive water resources are relentlessly in decline along the tropical belt, and water conflicts ever more likely in the twenty-first century (Gleick et al. 2009).


The Research Team

For our purposes we divide the Río Ica watershed into three sectors: the upper, middle and lower valleys. Work in all three sectors has been apportioned according to respective specialities. 

Dr Kevin Lane has focussed on the upper valley segment together with a Peruvian co-­director, Oliver Huamán. Dr David Beresford-­Jones, Dr Sandy Pullen and Susana Arce, Director of the Museo Regional de Ica have carried out investigations in the lower valley. Oliver Huamán and George Chauca have undertaken additional surveys and studies of the middle valley. All the project teams work under the direction of Professor Charles French, who has direct input particularly into its geoarchaeological components. 

Other project participants include Dr Lauren Cadwallader (isotopes, University of Cambridge), Dr Rob Scaife (pollen, Southampton University), Dr Fraser Sturt (GIS, Southampton University) and Dr Jonas Berking (hydrological modelling, FU Berlin). Leanne Zeki and Maria Angélica Garcia are working on MPhil's using GIS and archaeobotanical data, respectively, from the project. Meanwhile, undergraduates from the University of Cambridge, the Universidad Nacional Mayor de San Marcos, Lima and the Universidad Nacional San Luis Gonzaga de Ica have made important contributions to the project's fieldwork.



To answer the research questions defined above, we seek to combine archaeological field methods with the GIS mapping, geoarchaeological and archaeobotanical techniques.

Last year we excavated a Preceramic shell midden 'L-­1' (c. 5000 BC ) at the river estuary, alongside a detailed survey of the river mouth and adjoining shoreline and lomas fog meadows, each of which provided specific resources for its ancient fisher-­hunter-­gatherer inhabitants. This work suggests great shifts in the local estuarine ecology as a consequence of marine transgression and changes in shoreline morphology, which may have driven a move towards greater sedentism, agriculture and settlement further inland.

By the Late Intermediate Period (AD 1200–1450) this process had culminated in extensive irrigation on the coast, and vast terracing systems in the highlands. Concurrent excavations at 'H-­8' Samaca (at 250 m asl) and Sangayaico (at 3,800 m asl) are revealing the gradual accumulation of that hydraulic landscape. The wealth of material culture recovered in stratigraphic association at these sites will allow us to explore coast-­ highland interactions through GIS work.

Meanwhile, on-­going geomorphological and archaeobotanical analyses of highland moors, terraces and coastal middens, together with a GIS data base of all extant archaeology and hydraulic modelling will help us track the development of cultural adaptations along the Río Ica and understand concomitant environmental and climate change.



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