Changing river courses: reading Punjab’s archaeological landscape

Dating the channel

A palaeochannel is a trace of an earlier river course. Its presence near an archaeological site does not establish that a large river flowed there while people occupied the settlement. Ajit Singh and colleagues tested that relationship in the Ghaggar–Hakra region by studying sediments, their ages and their source. Their 2017 study identified the buried sands as evidence of an earlier Sutlej course.[1]

The researchers combined the character of sediment layers with mineral evidence and optically stimulated luminescence dates from sand grains. They concluded that the Sutlej’s diversion was complete shortly after about 8,000 years ago, well before the urban Indus settlements considered in the paper. In this reconstruction, those settlements developed along an abandoned valley, rather than beside an active, large Himalayan river in that same channel.[1]

An abandoned valley

The study proposes that the abandoned valley offered relative stability compared with a large Himalayan river liable to flood or shift laterally. This challenges the assumption that losing a major river always makes a landscape unusable. It also separates the date of a river’s change from later urban decline. The conclusion applies to the studied palaeochannel and should not be extended to every Indus city.[1]

Floodplains and monsoon change at a wider scale

Liviu Giosan and colleagues’ 2012 study examined broader Indus fluvial landscapes. Its abstract reports increasingly stable river landscapes as aridity intensified after about 5,000 years before present. The authors argue that reduced flood intensity could initially favour farming and urbanisation, while a further decrease in monsoon rainfall later harmed both flood-dependent and rain-fed agriculture. This is a proposed sequence of changing opportunities and stresses, rather than one sudden event.[2]

The study associates later changes with smaller settlements, crop diversification and a shift in settlement concentration towards wetter eastern regions. This interpretation does not mean every settlement moved at once, or that climate alone explains social decisions.[2]