Streamflow Generation by Variable Source Area
For many years, hydrologists and engineers alike have attempted to describe and model the processes that generate streamflow from rainfall. Modern understanding of runoff processes expanded rapidly in the twentieth century. Horton (1933) proposed that the soil surface partitions rainfall into overland flow and ground water. Simply stated, when rainfall rate exceeds the infiltration capacity of the soil, the excess water flows over the surface to become the primary source of storm flow. Base flow, that which maintains streams between rains, issues from ground water aquifers sloping gently to the channels. During the 1930s and 1940s, Horton and his coworkers firmly established the idea that infiltration was dominant in the runoff process. The central criticism of the Hortonian concept is that too much emphasis was placed on rain that fails to infiltrate the soil, and not enough on that which does infiltrate.
KeywordsUnsaturated Soil Overland Flow Subsurface Flow Runoff Process Impervious Area
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