HYDEX is a relational database that contains inventory information on the various streamflow, water level, and sediment stations (both active and discontinued) in Canada. This database contains information about the stations themselves such as: location, equipment, and type(s) of data collected.

HYDAT is a relational database that contains the actual computed data for the stations listed in HYDEX. These data include: daily and monthly means of flow, water levels and sediment concentrations (for sediment sites). For some sites, peaks and extremes are also recorded. The data are collected by the regional offices and updated in the national database once per year.