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United States Department of Agriculture

Agricultural Research Service

Title: An Integrated Systems Approach to Modeling Sediment Yield from Rangeland Watersheds 1305

Authors
item Nichols, Mary
item Lane, Leonard

Submitted to: American Society Of Civil Engineers Watershed Management Conference
Publication Type: Proceedings
Publication Acceptance Date: June 20, 2000
Publication Date: June 20, 2000

Interpretive Summary: Soil degradation in arid and semiarid ecosystems is a significant problem. Knowledge of sediment yield at the outlet of watersheds is insufficient to interpret internal watershed erosion and deposition processes. A mathematical model called APOINT is available to simulated sediment transport. Through the processes of calibration and validation the model can be established as a viable tool for predicting sediment transport and yield on semiarid rangeland watersheds. The model was calibrated and validated at small semiarid watersheds within the USDA-ARS Walnut Gulch Experimental Watershed near Tombstone, Arizona. The APOINT model was able to explain between 85 and 98 percent of the variation in observed sediment discharge from a 3.68 ha subwatershed located in the upper end of a 43.7 ha watershed. To further test the model, APOINT was calibrated at the outlet of the 43.7 ha watershed by comparing model results with observed sediment accumulation in the pond located at the watershed outlet. APOINT was able to explain 77 percent of the variation in sediment accumulation. An integrated system is under development to link the model and a relational database, and interpret model results with respect to zones of erosion, transport, and deposition within the watershed.

Technical Abstract: Soil degradation in arid and semiarid ecosystems is a significant problem. Knowledge of sediment yield at the outlet of watersheds is insufficient to interpret internal watershed erosion and deposition processes. An integrated system is under development to incorporate databases containing channel cross section information, a sediment yield model (APOINT) that is applicable to individual cross sections along alluvial channels, and interpreted model output. The APOINT sediment transport model was calibrated and validated at small semiarid watersheds within the USDA-ARS Walnut Gulch Experimental Watershed near Tombstone, Arizona. The APOINT model explained about 85 percent of the variation in observed sediment discharge from a 3.68 ha subwatershed located in the upper end of a 43.7 ha watershed. Results of model validation at the same watershed indicate that APOINT is able to explain 98 percent of the variation in observed sediment discharge. APOINT was further calibrated at the outlet of the 43.7 ha watershed by comparing model results with observed sediment accumulation in the pond located at the watershed outlet. APOINT was able to explain 77 percent of the variation in sediment accumulation during 7 time periods from 1962-1996. An integrated system is under development to link the model and the database, and interpret model results with respect to zones of erosion, transport, and deposition within the watershed.

Last Modified: 7/22/2014
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