Snow and glacier contribution to river flow

Snowpack and glaciers act as natural reservoirs, storing winter precipitation and releasing it through the dry season — which is when it is most needed.

Snow water equivalent: The depth of water a snowpack would produce if it melted. This — not snow depth — is what matters for water supply.
Why the timing matters: Snow and ice release water in summer, when rainfall is lowest and demand highest. Losing them shifts flow to winter, when it is least useful and most likely to flood.
Peak water: Glacier-fed rivers experience rising flow while ice is being lost, then a permanent decline. The temporary abundance is often mistaken for security.

Text description

Winter precipitation falls as snow in the mountains and accumulates as snowpack, with a portion added to glacier ice. In spring, snowmelt produces a large flow peak. Through summer, continued glacier melt sustains river flow when rainfall is low. As glaciers shrink, the summer contribution first increases as more ice melts, then declines permanently once the ice is gone.