Using AWM and SPAW For Evaluating Animal Waste Storage Structures

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The AWM (Animal Waste Management) software is primarily a design tool.  It has been traditionally used for designing animal waste storage structures (tanks, ponds, lagoons, etc).  Recently, it was upgraded to incorporate the evaluation function that enables the user to evaluate existing animal waste storage structures for their design adequacy.  On the other hand, SPAW (Soil-Plant-Air-Water) is a water budgeting tool for farm fields, ponds and inundated wetlands. The SPAW model performs daily hydrologic water budgeting using a modified SCS Runoff Curve Number method. The POND module of the SPAW simulates a water budget for a small pond/ reservoir/lagoon as well as performs statistical analysis of pond inundation cycles based on the wetland growing season. The SPAW water budget outputs from one or more fields are used as input for the POND module.   This paper demonstrates, with an example, how these two tools (AWM & SPAW) can be used for evaluating existing animal waste storage structures for adequate design and operational feasibility.  The AWM evaluates the capacity of the designed dimensions for the waste flowing into the structure and inflow from the extreme storm events; and the SPAW evaluates operational feasibility using long term simulations based on daily input of waste, rainfall, and other hydrologic interactions.  The paper also elaborates the data sources such as soils, climate, evaporation, etc. and the process of compiling and formatting these data for SPAW simulations


Harbans Lal, USDA/NRCS    

Pat Willey, Punya Khanal


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