WEPP ACTIVITIES: 1989 to 1995Beginning in late 1989, further WEPP model development became largely the responsibility of personnel at the USDA‐ARS NSERL in West Lafayette, Indiana. As WEPP Project Leader, J. M. Laflen supervised project activities, coordinated the efforts of team members across the U.S., and was responsible for soil erodibility parameteri- zation. M. A. Nearing served as WEPP Technical Director from 1992 to 1995 and led model testing, hydrologic parameterization, and model validation efforts. D. C. Flanagan was responsible for further development of the WEPP Hillslope Profile Model, interfaces, and documentation. Development of the WEPP Watershed Model was the responsibility of J. C. Ascough II. During 1989‐1995, many components were added to the model code that had been intended but were not included in the 1989 release. New and/or improved components incorporated into WEPP included non‐uniform hydrology, irrigation, winter processes, subsurface drainage, plant growth, residue decomposition, channel hydrology, channel erosion, and impoundment sedimentation. Other NSERL employees who assisted with WEPP activities included: J. G. Arnold, C. Baffaut, L. A. Deer, C. C. Drungil, J. E. Ferris, K. A. Franzmeier, A. J. Ketchum, S. J. Livingston, B. Liu, C. R. Meyer, L. M. Risse, D. E. Stott, G. A. Weesies, D. A. Whittemore, and X. J. Zhang.A documented and validated WEPP model (v95.7) was presented to user agency representatives at a special symposium sponsored by the Soil and Water Conservation Society on August 9‐11, 1995, in Des Moines, Iowa. The symposium included technical sessions describing the scientific components of WEPP and WEPS, and a model demonstration and training workshop. During a formal presentation ceremony, copies of the model software were provided on a multi‐media CD‐ROM to federal agency representatives (Flanagan, 1995; Flanagan et al., 1995). Paper documentation (Flanagan and Nearing, 1995; Flana- gan and Livingston, 1995) was also distributed to ARS, BLM, FS, and SCS employees and all symposium par- ticipants.The 1995 model release included a DOS‐based interface, originally created to expedite model testing and validation by individuals developing WEPP (Flanagan et al., 1994). From 1988 to 1992, SCS employees worked on development of their own OCP (operational computer program) interface but abandoned that effort in 1993. The WEPP DOS interface allowed simulation of both hillslope profiles and watersheds. However, it was almost entirely text‐based and difficult for some users to understand and apply.Substantial changes in both federal soil conservation programs and computer operating systems occurred from 1994 to 1996. SCS was reorganized into the Natural Resources Conservation Service (NRCS) on October 14, 1994, shifting its focus from preservation of soil resources to protection of air, soil, water, and wildlife habitat. The SCS Technical Centers were closed as part of the reorganization,disrupting many of the close working relationships established among ARS and SCS employees. During this period, personal computer operating systems were shifting from a text‐based MS‐DOS format to a graphically based Microsoft Windows structure. In addition, PC microprocessors were doubling in speed about every six months.
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