What is the difference between a storm drain and a dry well?

A storm drain is a large-volume storm water management system that captures water at the surface at grated “catch basins” and collects and consolidates water from a large area. Most drains have a single large exit at their point of discharge into a canal, river, lake, reservoir, sea or ocean. A dry well collects water in a similar fashion at the surface, but is designed to discharge slowly into the soil and is meant only for small volumes of water.