How do alpine lakes stay so clear in high mountains?

High mountain lakes often look especially clear because their catchments are steep, rocky, and thinly soil-covered, so fewer fine sediments and nutrients wash in. Cold temperatures also slow plant growth and decomposition, which can limit algae and keep the water transparent. Some alpine lakes are fed mainly by snowmelt or glacier melt, though glacial flour can make the water cloudy where active ice is present. Because mountain watersheds are often small, the lakes may respond quickly to changes in climate and snowfall. Their clarity makes them valuable indicators of environmental change.