Hydrologic and Water Quality Modeling of a CAFO Dairy Lagoon

Abstract:

Much of U.S. and global livestock production has moved from small, grazing operations to large Concentrated Animal Feeding Operations (CAFOs). These operations can produce as much waste as some cities, which is often stored in lagoons, pits or barns prior to field application or transport to other farms. Water quality near CAFOs can be impaired through multiple mechanisms: accidental or intentional release of lagoon waters, storm runoff from the feedlot or after manure applications, or lagoon seepage. Simulating trade-offs in CAFO manure lagoon management in a modeling framework has been difficult because of data paucity and a lack of available hydrologic models. We built an integrated hydrologic and water quality model for simulating CAFO lagoon hydrology and water quality. This model incorporates equations from SWAT and analytical equations for groundwater solute transport. Two groundwater quality assessments of dairies in Washington were used to calibrate and validate this model. Groundwater quality downstream of the lagoon was impaired due to seepage. The long-term effects of this lagoon on water quality are explored as well as the effectiveness of improving the lagoon lining to reduce . This model can be used to improve understanding of the impacts of CAFO lagoon seepage and can be extended to other CAFO sites to support sustainable management practices at the watershed scale for these key components of the agricultural landscape.