Quantification of nitrate budget from irrigated lands in Central Valley of California using SWAT
Abstract
A new regulatory program involving virtually all growers in California's Central Valley is underway with the aim to protect groundwater from nitrate contamination through irrigated agricultural lands. Growers are required to assess the effects of crop management practices on groundwater quality. This is especially challenging given the diversity of environmental and management settings, with >200 crops grown on >6 million acres of land. To comply with this requirement, growers opted to simulate root-zone nitrogen and water budgets for a variety of crop management (tillage, irrigation, and fertilizer application) practices and the full range of soil, and climate conditions encountered, all at a landscape scale. The Soil and Water Assessment Tool (SWAT), a physically based, continuous landscape model, was attributed and calibrated to quantify nitrogen and water budgets over this large area and range of settings. Extensive, aggregated and disaggregated, soft and hard calibration of hydrology (ET), crop growth (yield and biomass), and nitrogen budget (nitrogen uptake and nitrogen removed in harvest) were performed for more than 30 individual crops (covering about 99% of the irrigated acreage). To facilitate model runs, the Central Valley region was subdivided into three discrete modeling domains, respectively comprising the Sacramento, San Joaquin, and Southern San Joaquin valleys (the latter being approximately contiguous with the Tulare Lake Basin). A results viewer was developed so that growers and their advisers may view output relevant to fields they manage. Applied nitrogen and water in excess of crop needs resulted in insignificant increase in biomass and yield, but perceptible increases in leaching rates. These results were consistent across major acre crops, including almonds, citrus, and tomatoes. These results can be linked to groundwater tools to assess the influence of management systems on groundwater quality.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H41R1998M
- Keywords:
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- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1831 Groundwater quality;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY