Evolution of NRCS Hydrologic Methods through Computers

Abstract

The Natural Resources Conservation Service (NRCS), formerly known as the Soil Conservation Service (SCS), has developed hydrologic procedures for ungaged watersheds. NRCS initially used manual procedures to design conservation measures at the farm level. The agency was authorized to make small watershed studies in 1954 and this encouraged NRCS to develop uniform manual procedures that could be used for ungaged watersheds across the United States. As computers became available, NRCS used them to develop and refine hydrologic procedures. This paper will explain the evolution of the current hydrologic procedures. History The Natural Resources Conservation Service (NRCS) was established in 1933 as the Soil Erosion Service with the primary purpose of reducing soil erosion (Rallison 1980) and became the Soil Conservation Service (SCS) with the passage of the Soil Conservation Act of 1935. SCS became NRCS in 1994. In 1933, NRCS began to develop manual procedures to design measures to provide soil and water conservation at the farm level. These procedures included methods to provide peak flow estimates and tended to vary by regions. Designers and engineers used what was available in the literature. The Flood Control Act of 1936 required NRCS to develop hydrologic procedures at the watershed level. It authorized NRCS to make improvements in 11 watersheds. NRCS worked with various consultants and experts within the agency to develop