What is a base year and why is it used in SPARROW models?
|Back to Top| In general, the SPARROW model predictions of nutrient sources and loads reflect long-term mean annual nutrient conditions in streams. A statistical procedure is used (see question #2) to ensure that the model predictions reflect long-term hydrologic and water-quality variability during a consistent time period, which produces robust model predictions of nutrient sources and transport processes.The model predictions of the mean annual load for the calibrated model are standardized to a single year referred to as the base year to give an estimate of the mean nutrient load that would have occurred in streams during that year if mean annual flow conditions had prevailed. The designated base year for a SPARROW model is usually chosen to ensure consistency with other ancillary data used in the model, including nutrient-source data, land use, climate, stream networks, etc. Land-cover data (USGS National Land Cover Data or NLCD) are only available for specific years, typically at
