Tourists flock to see the rapids at Tiger Leaping Gorge along the Jinsha River, a primary tributary of the upper Yangtze River, Yunnan Province, southwestern China. A proposed holistic study of Asia’s mega rivers, including the Yangtze, would provide a more complete picture of how human influence affects rivers such as these. Credit: Steven A. Kuehl

Asia’s Mega Rivers - Common Source, Diverse Fates

How do humans affect the ways that Asia’s mega rivers deliver sediment and dissolved matter to farms, river deltas, and, eventually, the sea? A proposed study would construct an integrated picture.

Asia’s rivers affect more than half of the world’s population, providing water for cities, agriculture, transportation, and power generation and contributing to flooding and landslide hazards. These rivers also play important roles in many physical and biogeochemical processes on Earth’s surface, shaping the landscape and conveying huge quantities of water, sediment, and dissolved constituents to marginal seas—the regions that separate coastal zones from the open ocean.

“Mega rivers” in Asia—considered here to be those with historical annual sediment discharge of about 100 megatons per year or greater—share a common source in the Himalaya and Tibetan Plateau region (Figure 1), but a wide range of human and natural factors influences their fates. In many of these long, large river systems and their receiving basins, human activity (e.g., dam construction, agriculture, river management, trawling) has dramatically changed the length of time that particulate and dissolved matter spends in the river on its journey to the ocean.

Of particular concern in these rivers is human alteration of the transit and sequestration of water, sediment, and bioactive elements like carbon, iron, sulfur, phosphorus, nitrogen, potassium, and silicon. Anthropogenic changes to these fluxes affect the sustainability of deltas and coastal oceans, in turn imposing profound consequences on society that have only recently begun to be appreciated. We must understand the ongoing changes in fluxes and fates for river-derived materials to understand current impacts and predict future trends concerning such socially relevant issues as the global carbon budget and ocean acidification, eutrophication, pollution, and coastal erosion.

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