Laguna Watershed Knowledgebase

The non-point source pollution Soil Water Assessment Tool (SWAT) from the U. S. Department of Agriculture has been applied to understand management options that may improve water quality in the Laguna de Santa Rosa watershed. SWAT model output was first checked against six stream flow gauges in the watershed. At the monthly time-step, it was found that the pre-calibrated model performed well at all gauges. Calibration by modifications of ground water extraction in the watershed resulted in notable increases to correlation values at all gauges, except at upstream locations on Santa Rosa Creek and Mark West Creek. Measured seasonal trends in sediment concentrations were tracked closely by the SWAT model predictions. Highest sediment loading rates were associated in the model results with pasture, rangeland, and vineyard cover areas. Model scenarios have been tested for vegetation filter strips and improved ground cover conditions applied in sub-basins where soil erosion was shown to be elevated in previous simulations.