Peru has the largest mass of tropical glaciers in the world, mostly part of the Cordillera Blanca. Studies have indicated that the glacier mass has shrunk 20-30 percent since 1970 and is currently decreasing by 3 percent per year and the decline is accelerating.
Most importantly, the Santa River which receives water from the glaciers, has passed its “peak water,” after which the amount of discharge from the glaciers drops off sharply.
The back story for the Peruvian experience is that agriculture was built up in recent years taking advantage of the glacial flow – just as the flow started to diminish.
This sets up a conflict for various users of the water, which is likely to be duplicated in many parts of the world so affected. The military has identified this conflict as central to future military conflict. At the very least, more efficient water-use will be a necessity for many years.