In hydrology, discharge is the volumetric flow rate (volume per time, in units of m /h or ft /h) of a stream. It equals the product of average flow velocity (with dimension of length per time, in m/h or ft/h) and the cross-sectional area (in m or ft). It includes any suspended solids (e.g. sediment), dissolved chemicals like CaCO 3 (aq), or biologic material (e.g. diatoms) in addition to the water itself. Terms may vary between disciplines. For example, a fluvial hydrologist studying natural river systems may define discharge as streamflow, whereas an engineer operating a reservoir system may equate it with outflow, contrasted with inflow.