Presentations 2016

The Central Valley Dairy Representative Monitoring Program – Insight from 4 Years of Monitoring and Special Studies

LSCE

https://www.youtube.com/watch?v=gIeTgBx9ToM&list=PLZC-5vj9_JAYJ9uI2abX-KQy56Nl6HTmI&index=1

Since 2012, the Central Valley Dairy Representative Monitoring Program (CVDRMP) has been implementing a regulatory compliance groundwater monitoring program in the Central Valley of California spanning over 600 kilometers from north to south. The climate is semi-arid with hot, dry summers and cool winters with the majority of precipitation occurring between November and March. CVDRMP represents over 1,100 dairies, diverse soil and farming conditions, and collects data in over 430 dedicated monitoring wells adjacent to animal housing, earthen liquid manure storage lagoons, and fields where both liquid and solid manure is applied to fertilize forage crops. The program is tasked to identify farming practices that are protective of groundwater quality and formulate recommendations in 2019.Four years of groundwater monitoring have confirmed impacts to shallow groundwater quality associated with dairy operations. Elevated nitrate concentrations and salinity are ubiquitous and impart a trademark on groundwater similar to other, non-dairy agricultural operations. However, the overall utility of groundwater monitoring has been found to be limited.Regulatory attention was initially focused on lagoons. The program found that groundwater monitoring is not an effective means of investigation in the context of lagoons. Groundwater constituent concentrations do not yield information on concentrations in the leachate, the seepage rate, the overall mass loading rate, or the duration of the loading. To address this issue, CVDRMP conducted a comprehensive field investigation quantifying whole lagoon seepage rates. Seepage rates were small, ranging from zero to 2.2 mm d-1, with a mean and median of 1.0 and 0.7 mm d-1, respectively (n=16). Lagoons ranged in age from less than 10 to over 50 years, i.e., many of them predated regulations or guidance for lagoon liner design. Subsurface soil textures ranged from sand to silty clay, but seepage rates did not correlate well to soil texture. One lagoon, where exposed gravel strata are suspected, had a seepage rate of 3.9 mm d-1 when at full capacity. Seepage rates and the mean nitrogen mass loading rate of 1,172 kg ha-1 y-1 were consistent with findings of other research efforts. Complementary soil borings and geophysical methods documented that effects of lagoon seepage on groundwater quality are generally small and remain localized. Based on preliminary land base and unit loading rate estimates from 41 dairies, lagoon contributions were estimated to be 2.3-3.5 percent on a farm scale compared to 96.5-97.7 percent from crop fields (animal housing including corrals not included)The program identified groundwater monitoring as similarly ineffective in the context of assessing farming practices on the crop fields. Improvements in agricultural practices, including improved nutrient use efficiencies, manifest themselves in reduced subsurface nitrogen and salt mass emissions; this reduction is not necessarily observed in concentration decreases at the water table. To address this issue, CVDRMP is carrying out several research studies tackling the difficult task of nutrient management in full-scale production systems that heavily rely on organic sources (i.e., manure) for fertilization.