Modeled Nitrate Effects to Groundwater for Different Crops under On-Farm Flood Capture and Recharge (OFFCR); Cultural Practice Recommendations

Collaborating Organizations

Sustainable Conservation, Tetra Tech, Kings River Conservation District, Bachand & Associates, UC Davis, UC Cooperative Extension, Luhdorff & Scalmanini Consulting Engineers

Project Summary

As 2014 Sustainability Groundwater Management Act (SGMA) goals encourage recharging groundwater, nitrate leaching concerns are raised. Increases in nitrate in the groundwater pose serious health concerns: respiratory illness, cancer, methoglobinemia. Nitrate is added to the soil as commercial fertilizer, manure, or irrigation water. Recharge has the potential to flush root zone nitrate into the groundwater, degrading groundwater quality.

In this study, we tested On-Farm Flood Capture and Recharge (OFFCR) effects on water quality and contaminant transport. We collected data of three crop types (i.e, Tomatoes, Grapes, Almonds) over two soil hydrologic classifications (i.e., A, C/D). We took soil cores to analyze nitrate, salts, and moisture. We monitored fertility and irrigation timing and application rates as well. We developed an integrative groundwater model with vadose zone modelling and parametrized the model using core profiles and measured flushing rates during recharge events. The hydrus model mass transport calibration projected the cumulative mass of nitrate per depth over time. The project resulted in 30-50 ft of water flushing legacy nitrate from vadose zone. Results included: greatest nitrate count in proximity to recharge in first decade, groundwater quality effects differ by crop and management, effects diminish with distance and time.

Publications

Bachand, P. 2018. Modeled Nitrate Effects to Groundwater for Different Crops under On-Farm Flood Capture and Recharge (OFFCR); Cultural Practice Recommendations. Maintaining Groundwater Quality. University of California Davis. September 5 -6, 2018.

P.A.M. Bachand, S.M. Bachand, H. Waterhouse, J. Rath, M. Ung, S. Roy, V. Kretsinger, B. Dalgish, W. Horwath, H. Dahlke, C. Creamer, J. Choperena, and D. Mountjoy. Technical Report: Modeling Nitrate Leaching Risk from Specialty Crop Fields During On-Farm Managed Floodwater Recharge in the Kings Groundwater Basin and the Potential for its Management. Available from Sustainable Conservation, Published: 2017.