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Mountain basin hydrologic study




Woolridge, Douglas D., author
Niemann, Jeffrey, author

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A long-standing problem for the Rocky Mountain region is that traditional meteorology and flood hydrology methods appear to significantly overestimate floods based on comparisons to paleoflood evidence and regional peak streamflow statistics. The Colorado Water Conservation Board (CWCB), Colorado Division of Water Resources (DWR), and state of New Mexico are conducting a $1.5 million study to develop improved estimates of extreme precipitation for the two-state region. Concurrently, DWR has been working to improve flood hydrology methods for the mountain region. Traditional flood hydrology methods utilize low infiltration rates to model flood runoff solely by an infiltration-excess mechanism. However, a recent but preliminary examination of the Gross Reservoir Basin suggests that saturation-excess runoff might be important for extreme precipitation events. The objectives of this research project are: (1) to determine the importance of saturation-excess runoff production for large storms that affect the design and performance of dams and transportation infrastructure and (2) to develop a generalized model for runoff production in mountainous basins that can be used by consultants to perform hydrologic analysis of dams and transportation infrastructure. In-situ soil moisture observations indicate that south-facing slopes often reached saturation during the September 2013 flood while north-facing slopes usually did not. They further suggest that saturation occurred first at the bottom of the soil layer and proceeded upward. These observations are consistent with saturation-excess runoff production. The preliminary model results also indicate that saturation-excess runoff production was the primary runoff production mechanism in South Boulder Creek during the September 2013 flood. Additionally, the model results show that south-facing slopes approached saturation while the north-facing slopes did not.


December 2018.

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September 2013
South Boulder Creek (Colo.)
Gross Reservoir (Colo.)
extreme events
runoff production
hydrologic response


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