Nitrogen and Salt Loading to Groundwater from Concentrated Animal Facilities

Quantitative subsurface loading estimates from earthen corrals and liquid manure ponds are critically import to the Central Valley dairy community to effectively guide efforts to reduce industry-wide impacts on groundwater quality.

We devised and implemented a multi-faceted approach, including geophysical methods, continuous soil coring and sampling, depth-specific pond sampling, groundwater sampling from monitoring wells and temporary soil borings, direct pond seepage testing, and mass balance computations. Daily pond seepage rates are quantified in the sub-millimeter realm, including a specified uncertainty.

Results show corrals and liquid manure ponds are minor contributors to subsurface mass loading on an industry-scale, while irrigated cropland requires attention.

Significant Project Elements

• Research methodology
• Experimental design and field work
• Resistivity profiling to delineate local effects
• Continuous soil coring
• Soil sampling
• Groundwater sampling
• In-situ pond seepage testing
• Boundary condition modeling
• Constituent mass accumulation computations
• Mass flux estimates