Thursday, May 22, 2008

Water supply and history: Sarasvati river basin


Antiquity Vol 82:315, March 2008, pp 37-48. Rita Wright et al.

Water supply and history: Harappa and the Beas regional survey

Rita P. Wright, Reid A.Bryson and Joseph Schuldenrein

1 Department of Anthropology, New York University, 25 Waverly Place,New York 10003, USA (Email: rita.wright@...)
2 Center for Climatic Research, University of Wisconsin, 1225 W.Dayton St., Madison, WI 53706-1695, USA (Email: rabryson@...)
3 Geoarchaeology Research Associates, 5912 Spencer Avenue,Riverdale, New York 10471, USA (Email: geoarch@...)

Introducing the methods of archaeoclimatology, the authors measure the relative locus of the monsoons, the intensity of winter rains and the volume of water in the rivers in the Upper Indus, in the region of Harappa. They also note the adoption of a multi-cropping agricultural system as a possible strategy designed to adjust to changing conditions over time. They find that around 3500 BC the volume of water in the rivers increases, and the rivers flood, implying annual soil refreshment and the consequent development of agriculture. By contrast, from around 2100 BC the river flow begins
to fall while the winter rains increase. This time-bracket correlates nicely with the brief flourishing of Harappa. The locally derived evidence from Harappa combined with the Beas survey data provide a model for understanding the abandonment of settlements in the Upper Indus and possibly the wider civilisation.

The study notes that though the Ghaggar-Hakra (Sarasvati River Basin) was once dynamic, it ceased to supply water to this region at some time in the past.

The focus of this paper is on the history of the river and its interaction with the local climate and their impacts on agricultural systems in the Upper Indus. Specifically, the study addresses the environmental conditions under which settlement and agriculture developed in the Upper Indus, in the area of the city of Harappa and along the nearby Beas river, where 18 Indus settlements have been discovered.

Site locations of Harappa and the regional Beas survey are:
1. Lal Tibbe; 2 and 3. Chak Purbane Syal; 4. Chak 90-12; 5. Kusamsar; 6. Chak 75-15; 7. Bagh Thal; 8. Vainiwel; 9. Chak 104-10R; 10. Chak 113-10R; 11. Chak 123-10R; 12. Chak 133-10$; 13. Chak 160-WB; 14. Qutab Pur; 15-18 Dunyapur Complex

Of these 11 sites were founded on the Beas river. By 2600 BCE, Beas settlements numbered 18, one was 14 ha, four were between 5-10 ha and the others were less than 5 ha.

The authors claim to introduce a new tool for exploring climatic environment of ancient cultures called Archaeoclimatology, a high-resolution, site-specific climate model. By 1300 BCE, Harappa was perhaps abandoned and at that time, only four Beas sites were sustained.

Tracing Intertropical Convergence History (ITC) of monsoons, the authors note that “For millennia, the land was marginal for rain-fed agriculture…Suddenly about 3600 BCE there was a dramatic change o higher energy stream flow with much more discharge. Increased stream dynamism persisted for 1500 years (c. 2100 BCE). If anything, precipitation decreased locally. These hydrographic changes probably promoted the development of riverine agriculture.” In conclusion, they note: “Though the Ghaggar-Hakra was once dynamic, it ceased to supply water to this region at some time in the past…The hydrographic and climatic models presented here suggest that at around the time of the Harappan emergence, stream activity and precipitation patterns underwent dramatic transitions following over 4000 years of Holocene stability. Geomorphological and pedological evidence points to realignments of channels in the immediate vicinity of the Harappa site, as the Ravi River migrated north during the Late-Harappan period (c. 2000 BCE) and soils formed on relatively stable alluvial surfaces along the Beas…”

Read this doc on Scribd: ant0820037

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