a water reservoir stores water & glaciers are a kind of major reservoir ->  glaciers are a kind of water reservoir  glaciers are a kind of water reservoir & glaciers are a source of freshwater ->  glaciers are a kind of water reservoir that are a source of freshwater  glaciers are a kind of water reservoir that are a source of freshwater & a mountain glacier is a kind of glacier ->  mountain glaciers are a kind of water reservoir that are a source of freshwater  mountain glaciers are a kind of water reservoir that are a source of freshwater & a source of something provides that something -> mountain glaciers are a kind of water reservoir that provide freshwater