Browsing by Author "Molling, Christine C."
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- ItemTesting a Grid-Based Soil Erosion Model across Topographically Complex Landscapes(SOIL SCI SOC AMER, 2008) Bonilla, Carlos A.; Norman, John M.; Molling, Christine C.; Karthikeyan, K. G.; Miller, Paul S.This study was conducted to evaluate the overall performance of the Precision Agricultural-Landscape Modeling System (PALMS) for calculating runoff and soil loss under cropped conditions. The PALMS model uses a lognormal distribution of saturated hydraulic conductivity across the fields to simulate typical soil heterogeneity within soil texture classes. Runoff and soil loss data were collected in three farm fields for a total of 75 runoff events during 2 yr under six cropping scenarios (alfalfa [Medicago sativa L.] and corn [Zed mays L.] no-tilled, corn and soybean [Glycine max (L.) Merr.] moldboard plowed, and alfalfa and corn chisel plowed). For individual storms, calculated runoff and sediment loss from PALMS were compared with corresponding measurements for each farm during the entire cropping season. The coefficient of determination (r(2)) between runoff calculations and measurements was 0.84. The r(2) between soil loss calculations and measurements with the storm-by-storm simulations during both seasons was 0.78. Based on these continuous simulation results, the PALMS calculations appear to have lower relative errors with large events than small events, a desirable result because large events are most important in assessing the environmental consequences of management practices.
- ItemWater erosion estimation in topographically complex landscapes: Model description and first verifications(SOIL SCI SOC AMER, 2007) Bonilla, Carlos A.; Norman, John M.; Molling, Christine C.Two of the most important limitations when predicting soil movement are the natural complexity and the spatial heterogeneity of the processes. Sod erosion can vary significantly across short distances as a function of local soil properties and microtopography; but regardless of this, many erosion models assume homogeneity in topography and soil characteristics. The objective of this research was to develop a method for estimating soil loss from agricultural fields that is faithful to the complex topography and spatial heterogeneity common to managed landscapes. Sediment loss for individual storms was achieved by linking sod detachment-deposition equations adapted from the Water Erosion Prediction Project (WEPP) model to the existing water-flow subroutine in the Precision Agricultural-Landscape Modeling System (PALMS). In PALMS, sediment was routed appropriately in a two-dimensional grid, defining the pathways taken by the eroded material. Usually PALMS works on a grid-cell size of 5 to 20 m and simulates runoff and sod erosion patterns as affected by slope, soil texture, anisotropic surface roughness, soil consolidation, canopy cover, and tillage interactions with topography. In this study, PALMS and WEPP were used to simulate the sediment transport on an idealized field with a complex hillslope profile. Both models showed a consistent soil loss pattern and only minor differences in transport capacities. The models were also compared with data from actual erosion Plots, where both runoff and soil loss were predicted with similar errors for both PALMS and WEPP To illustrate the capability of PALMS, it was applied to a field with complex topography.