Luminescence Sensitivity as Proxy for Sediment Source and Transport – A Case Study from the Ganga River

We report the use of Luminescence sensitivity as a proxy to understand sediment dynamics in the Ganga River and its major tributaries, viz., the Yamuna, the Chambal and the Ramganga rivers in India.  The Ganga River is one of the world’s largest dispersal systems that originates in the Himalaya and travels across central India to meet the Bay of Bengal. The basin size, catchment lithology, climatic conditions and geomorphic processes of these large rivers are diverse. The rivers are classified into reaches based on varied morphometric characteristics. Sampling strategies focussed on point bars and mid-channel bars mostly from the low-gradient reaches of the rivers, and intervals such that the influences of local dimensions such as hillslope processes and smaller tributary confluences get integrated. Luminescence sensitivity (photon counts/unit dose/unit mass) of quartz grains of 90-150 µm size are examined after check on their purity.

The results suggest the following:

• A gradual change in luminescence sensitivity in the downstream direction.
• Change is slower at the beginning, then it increases to nearly twice the initial rates after the confluence with R. Ramganga suggestive of change in sediment flux and sediment transportation rates. In the upstream reaches of the river, influences of a landslide zone and the dun (intermontane valley) rivers are discernible.
• Rates of sensitivity change is nearly four times higher in the case of Yamuna River suggestive of longer transport times.
• Samples after the confluence of the Ganga and the Yamuna suggest variable contribution from the two rivers through time.
• Sensitivity of quartz suggests influence of tributary confluences on the change in luminescence sensitivity along the trunk rivers and offer prospect of developing it as an additional parameter to quantify river processes through time.

 

This project is supported through DST SERB-YoSCP grant.