Continuous Hydrologic Modeling of Snow-Affected Watersheds in the Great Lakes Basin Using HEC-HMS: Fid-Bau Portal

Continuous Hydrologic Modeling of Snow-Affected Watersheds in the Great Lakes Basin Using HEC-HMS

Gyawali, Rabi / Watkins, David W.

To reproduce historical stream flows, climate and land-use change studies require watershed models with physically based parameters, rather than empirical models that are simply calibrated. With this in mind, soil moisture accounting and the temperature index (degree-day) snowmelt models embodied in the Hydrologic Engineering Center’s hydrologic modeling system (HEC-HMS) are applied to three Great Lakes watersheds—Kalamazoo, Maumee, and St. Louis—with different climatic and land-use characteristics. Watershed and subwatershed models are calibrated and validated on a daily time step using gauge precipitation measurements, observed snow water equivalent data, and physically based parameters estimated using geospatial databases. Results are compared with area-scaled outputs from the National Oceanic and Atmospheric Administration (NOAA) large basin runoff model (LBRM) for historical conditions. The results show modest improvements resulting from the increased spatial resolution of the HEC-HMS models, in addition to the benefits of the more process-based snow algorithm in HEC-HMS, particularly for the snow-dominated St. Louis watershed. However, both LBRM and HEC-HMS models had difficulty reproducing peaks in late winter and early spring runoff, and discrepancies could not be attributed to any systematic errors in the snowmelt models.