Modeling pesticide loadings into the Sacramento-San Joaquin Delta: potential impacts on weed biological control

Start/End: April, 2016 to March, 2018

Each year, millions of dollars are spent in the Delta to prevent invasive weeds from obstructing navigation, reducing water quality, displacing native species and harboring mosquitoes. Biological control of aquatic weeds by insects – a promising means of mitigating – is not performing as well as expected. One likely reason for this may be the high levels of pesticides in the Delta waters, which are largely influenced by pesticide loadings from the upstream agriculture.

The goal of this proposed project is to quantify pesticide loadings into the Delta waterways using the Soil and Water Assessment Tool, SWAT.  Specifically, the project will:

  • Identify the patterns of pesticide use in the Sacramento and San Joaquin watersheds, and prioritize pesticides that have high impacts on biological control agents;
  • Calibrate and validate SWAT for simulation of stream flow, sediments and pesticides in the Sacramento and San Joaquin watersheds;
  • Assess the spatio-temporal patterns of pesticide loadings into Delta waterways using the calibrated SWAT; and
  • Explore the spatio-temporal relationships between aquatic weed abundance and water quality in the Delta.

This research will be used by the Delta Region Area-wide Aquatic Weed Project (DRAAWP), which includes five State and Federal agency partners and UC Davis researchers, to improve the management of aquatic weeds.