"glaciers are shrinking by an amount equivalent to all the water in the giant Yellow River each year."
Let's see.
Glaciers feed the rivers year round.
Soooo that means the amount of water in the rivers equals the amount of ice melting from the Glaciers?
Duh!
I interpret this to mean that the total amount of ice melted from the Chinese mountain glaciers in a year is equivalent to the annual flow of the Yellow River. Of course, the meltwater from the glaciers feeds many different rivers. The rivers obviously get water from other sources as well (like rainfall).
The problem that the article is talking about is that the glaciers are the only water source for rivers that run through the arid western part of China, much like Rocky Mountain snow and glacier melt feeds the Colorado River. If the glaciers are shrinking, that means that the "reservoir level" is dropping. If this reservoir disappears, the rivers essentially dry up.