Effects of Upstream Human Changes on Nutrient Fluxes to Major Deltas World-Wide

Abstract:

Major deltas world-wide are connected to large river systems, and while they make up <1% of the shoreline, they are at the receiving end of 25-42% of all discharge, suspended sediment load and nutrient load. Thus, in addition to the pressure from human impact in the deltas, changes far upstream are tightly linked to effects downstream. The Global-NEWS approach has explored scenarios along storylines that influence future nutrient fluxes, and if highlighted for individual delta, reveals large differences in future change, with most of the influence being attributed to factors such as land use change or increased damming. Notably the latter factor has received recent attention with regards to nutrient fluxes, and phosphorus (P) in particular (Maavara et al. in review): the largest increases in P retention by reservoirs, between 2000 and 2030, are expected to occur in the Yangtze, Mekong, Amazon and Ganges-Brahmaputra river basins. Here, we discuss how Global-NEWS and other approaches assess these future changes in nutrient fluxes, and how the expected new boom in dam construction can influence these fluxes to deltas world-wide.