Use of Plot Scale Observations to gauge the applicability of Physically-Based Models
Abstract
Catchment hydrologic modeling efforts should be initiated with a comparison between a perceptual model of how the basin functions, and what processes the numerical hydrologic model represents. The majority of recent attention in literature has been focused on using this process to inform conceptual model structures aimed at predicting streamflow from precipitation events. However, this method may also be used to assess the applicability of physically-based models when lumped parameter models are insufficient for research questions. Physically-based models are chosen over lumped parameter conceptual models for their ability to provide detailed spatial information on soil moisture, ephemeral streamflow, and differential snow melt. A plot scale study was conducted in a 0.02 km2 headwater catchment to build a perceptual model of the Tree Line (TL) Experimental Catchment within the Dry Creek Experimental Watershed (DCEW) in the semi-arid foothills north of Boise, ID. Overland flow, through flow, and radiation flux measurements were taken in addition to existing weather station variables (air temperature, relative humidity, wind speed and direction, snow depth, and soil moisture) for the 2011 water year. The 2011 water year is typical of this study site and is characterized by a shallow snowpack that lasts from the late fall to early spring and includes several rain-on-snow events. A soil storage field capacity threshold in the upper highly conductive soil (approximately 145 mm) must be crossed before lateral flow is observed. The total soil storage threshold for lateral flow slowly increases from 253 mm during a December rain-on-snow event, to 269 mm during the spring melt event as deeper, less conductive soils wet up. Lateral flow primarily takes place as overland flow and as concentrated flow paths at the soil-bedrock interface, which are controlled by bedrock topography. Results suggest that the watershed models used in TL need to account for unsaturated soil storage, the development of a shallow hillslope saturated zone, and lateral flow at the soil-bedrock interface. Both the snowmelt model and the watershed model need to account for commonly observed aspect differences in vegetation and insolation. Future work will assess the applicability of the coupled physically-based snowmelt model (SNOBAL) and physically-based watershed model (PIHM) to the 26.9 km2 DCEW.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H33H1418K
- Keywords:
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- 0764 CRYOSPHERE / Energy balance;
- 1804 HYDROLOGY / Catchment;
- 1805 HYDROLOGY / Computational hydrology;
- 1894 HYDROLOGY / Instruments and techniques: modeling