Uncertainty in critical source area predictions from watershed-scale hydrologic models
Abstract
Watershed-scale hydrologic models are increasingly applied to inform the placement (or 'targeting') of best management practices (BMPs) via identification of critical source areas (CSAs) (alternatively 'hotspots'), defined as areas that export disproportionally high quantities of nutrients or sediment. However, CSA predictions from watershed-scale hydrologic models may be uncertain. Understanding the extent and implications of this uncertainty is critical to efforts to apply these models to inform BMP targeting. We applied an ensemble of watershed-scale hydrologic models (SWAT and SPARROW models) to (1) predict CSA locations for phosphorus, nitrogen and sediment within the ~17,000 km2 Maumee River watershed, the largest tributary to Lake Erie, (2) quantify uncertainty in CSA predictions, assessed as variation in predictions of CSA location across ensemble models, (3) evaluate the extent to which model inputs (e.g., fertilizer application rates) drove CSA predictions, and (4) evaluate the utility of CSA predictions given our analysis of uncertainty and model assumptions. We found that (1) model inputs (e.g., fertilizer application rates) were the principal determinant of CSA location in the models, (2) CSA predictions were uncertain as ensemble models frequently disagreed with respect to CSA location, and (3) there was nonetheless sufficient agreement across model-predicted CSAs to support their use in BMP-targeting. Our results suggest that watershed-scale hydrologic models may be applied to identify CSAs but an analysis of CSA prediction uncertainty should accompany their application. Our results also suggest that improved input data (e.g., fertilizer application rates) may greatly reduce uncertainty in CSA predictions from watershed-scale hydrologic models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H43Q2307E
- Keywords:
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- 1848 Monitoring networks;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY;
- 1879 Watershed;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY