Wisler and Brater (59, p. 1) define hydrology as "the science that deals with the processes governing the depletion and replenishment of the waters of the land areas of the earth." Thus, hydrology is concerned with the transportation of the water through the air, over the ground surface and through the strata of the earth.
The manner in which water passes to a stream channel governs the terminology of the flow. The accepted components of stream-flow are interflow, ground water, channel precipitation and surface runoff. Of primary importance in this study is surface runoff, or water which passes to a stream channel by traveling over the soil surface. Its origin may be water arising from melting snow or ice, or rainfall which falls at rates in excess of the soil infiltration capacity.
Gray, Don M.
"Derivation of hydrographs for small watersheds from measurable physical characteristics,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 34
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol34/iss506/1