This article in the Guardian is of interest at the moment, especially since i have just spent the last two weeks writing a scheme of learning on Rivers! It's a start for the new OCR B GCSE specification (now on the OCR B GCSE Ning).
Some of the most important rivers on the planet, including the Ganges, the Niger, and the Yellow river in China, are drying up because of climate change, according to this article.
The map below shows the change in run-off inferred from streamflow records worldwide between 1948 and 2004, with bluish colors indicating more streamflow and reddish colors less. Graphic: Journal of Climate, modified by UCAR.