Hydroclimatology was defined by Langbein (1967) as the study of the influence of climate upon the waters of the land. It includes hydrometeorology as well as the surface and near-surface water processes of evaporation, runoff, groundwater recharge, and interception. The total hydrologic cycle, then, is the basis for a discussion of hydroclimatology.
where P is precipitation, R is streamflow, ET is evapotranspiration, U is subsurface underflow, ΔS s is the change in soil moisture, ΔSg the change in groundwater storage, and I is interception. When the equation is evaluated using annual mean data, the changes in groundwater storage, soil moisture and subsurface underflow are assumed to be zero; and if the interception is sufficiently small, all four terms may be deleted. Although the components of the total budget are easy to list, quantification of each