I came across this splendid, short summary on the state of knowledge of Asia’s Mega Rivers by Stephen Kuehl and colleagues. The authors make a strong case for a new, wide-ranging research program.
“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, 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.
In contrast to large river systems in North America and many other parts of the world, which have generally experienced human influences for hundreds of years or less, humans have been altering sediment loads in Asian mega rivers for more than 1,000 years. Today, human influences on the Yangtze are particularly acute, with many megacities (e.g., Chongqing, Shanghai), large dams (e.g., Three Gorges), and areas of dense industrialization lining its course and polluting its waters. The Yangtze supplies more plastic to the ocean than any other river and has experienced dramatic climate, land use, and dam-induced fluctuations of its water and sediment fluxes.
Worth a read.