Quoted from: Application of streamflow synthesis and reservoir regulation -"SSARR"- Program to the Lower Mekong River. David M.Rockwood, Chief, Hydrology and Hydraulics Section, North Pacific DivisionU.S.Corps of Engineers. http://hydrologie.org/redbooks/a080/iahs_080_0329.pdf

      The "SSARR" program is designed to create a mathematical hydrologic model of a river system through the use of an electronic digital computer. Streamflows can be synthesized by evaluating the entire hydrologic process of snowmelt and/or rainfall-runoff for all significant points throughout a river system. Drainage basins can be separated into homogeneous hydrologic units of a size and character which can be used as a logical delineation of major drainage into its component sub drainage. Channel storage can be specified for channel reaches to represent the natural delay to runoff encountered in a complex river system. Storage effects of lakes or man-made reservoirs can be evaluated in accordance with free-flow conditions or specified conditions of reservoir storages or withdrawals. Streamflows can be thus developed for all key locations on the main stem and tributary rivers.

      The program combines evaluation of various hydrometeorological functions to represent the entire process of streamflow simulation, as described by the standard conceptual model of the hydrologic cycle. It is designed to be completely general in nature, so that streamflow may be synthesized by adjusting the various parameters for a particular drainage basin that affect the evaluation of moisture input (either rainfall or snowmelt); soil moisture; evapotranspiration; depression storage; surface，subsurface, and ground water storage; infiltration to each of the aquifer zones; time delay represented by storage and flow relationships in each zone, and channel storage effects. When these parameters are evaluated for a given basin, they represent the calibration of a particular area or homogeneous unit.