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United States Department of Agriculture

Agricultural Research Service

Title: Example of an index validated by a model

item Baffaut, Claire
item Anderson, Stephen
item Mudgal, Ashish

Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2011
Publication Date: 3/29/2011
Citation: Baffaut, C., Anderson, S., Mudgal, A. 2011. Example of an index validated by a model [abstract]. Soil and Water Conservation Society - Modeling Summit, 03/29-31, 2011, Denver, CO. 15.

Interpretive Summary:

Technical Abstract: Practical and robust methodologies to determine where conservation should be implemented on the landscape remain to be developed. A method is proposed to identify sub-field areas that need conservation practices to reduce sediment, nutrient, and pesticide loss in a 32-ha field of the 72 km2 Goodwater Creek watershed, located in the claypan area in Missouri, USA. The field was divided into 35 subareas based on slope, depth to claypan, and soil mapping units. Runoff and water quality data collected at the outlet were used to calibrate the Agricultural Policy Environmental Extender (APEX) model. Simulated output by subarea was correlated with physical parameters including depth to claypan (CD), surface saturated hydraulic conductivity (Ksat) and subarea slope (SL). Two indices were developed, CD*Ksat /SL, and CD/SL, which correlated with runoff (r = -0.69), and atrazine (r=-0.56) and sediment loads (r=-0.50), respectively. These indices captured 100% of runoff and sediment yield critical areas and 60% of atrazine critical areas, as predicted by APEX; they also identified areas with lower productivity. In the second part of this study, the indices were calculated for each HRU of a SWAT model of the watershed, and correlated with the HRU output variables of interest. Upon verification that the correlation was good, the conservation need was based on these index values calculated for polygons resulting from the overlay of the field boundary and soil layers.The index method was easier to implement and could be used for identifying conservation needs in claypan areas without parameterizing a SWAT model.

Last Modified: 06/23/2017
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