FIGURE 3. Change in discharge versus change in discharge at average precipitation and change in precipitation for sub-watersheds of the Mississippi.
From the following article:
Anthropogenically enhanced fluxes of water and carbon from the Mississippi River
Peter A. Raymond, Neung-Hwan Oh, R. Eugene Turner & Whitney Broussard
Nature 451, 449-452(24 January 2008)
doi:10.1038/nature06505
The left panels show all watersheds, while the right panels show only watersheds with 70% or greater cropland land cover. The change was calculated by grouping the data before 1966 and after 1987. It is important to note that in sites with low agricultural cover (<30%), change in precipitation predicts 74% of the variation in change in discharge, while change in discharge at average precipitation can only predict 25%—that is, in forested watersheds changes in precipitation do balance changes in discharge.