Event Title

The Influence of Topography on Runoff for Selected Tributaries to the Salmon River, Idaho

Presenter Information

Christopher Tennant

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-21-2010 1:00 PM

End Date

4-21-2010 1:20 PM

Description

Understanding potential effects of climate warming on snow-dominated watersheds is confounded by several environmental characteristics. Major river basins experience non-uniform climate forcings caused by variations in latitude and elevation. These variations result in hydrologic heterogeneity at multiple spatial and temporal scales, making predictions about the effects of warming temperatures on surface runoff difficult. Here, we present current results from a study in the Salmon River Basin in central Idaho that highlight the influence of topography and climatic variability within a large river basin on the runoff character. Study tributaries are grouped into three precipitation regimes that were selected using hypsometry. High elevation (2500 - 3200 m) study catchments are dominated by snow and have smooth, broad hydrographs. Mid elevation (1500 - 2200 m) basins span elevations that receive both snow and rain. These hydrographs reflect characteristics of both snowmelt and rainfall runoff. Liquid precipitation dominates lower elevation catchments (400 -1500), with flashier hydrographs that exhibit low baseflows. The unique behavior of tributaries within different precipitation zones is further revealed by the temporal separation of peak flows within respective elevation/precipitation zones; peak runoff becomes progressively later with increasing elevation and the proportion of snow to rain. Data from our monitoring sites suggest that environmental lapse rate is a first order control on precipitation and that the characteristics of runoff within a given zone is largely controlled by the range of elevations that comprise the catchment. Hydrologic analysis of USGS gages along the mainstem Salmon demonstrate that more water is delivered per unit area from high elevation catchments located on the western edge of the Salmon River basin. This suggests that there is a strong orographical forced precipitation gradient in a west to east direction and demonstrates that discharge does not scale linearly with drainage area in the Salmon River basin. This analysis provides physically based measurements that 1) highlight the hydrologic heterogeneity present within a large river basin, 2) provide insights about the potential hydrologic evolution of watersheds if snowlines rise by utilizing a space for time substitution, 3) provide an elegant mechanism for understanding the topographic sensitivity of a basin to rising snowlines (hypsometry) and 4) challenge well established theoretical hydrologic scaling relationships.

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Apr 21st, 1:00 PM Apr 21st, 1:20 PM

The Influence of Topography on Runoff for Selected Tributaries to the Salmon River, Idaho

Eccles Conference Center

Understanding potential effects of climate warming on snow-dominated watersheds is confounded by several environmental characteristics. Major river basins experience non-uniform climate forcings caused by variations in latitude and elevation. These variations result in hydrologic heterogeneity at multiple spatial and temporal scales, making predictions about the effects of warming temperatures on surface runoff difficult. Here, we present current results from a study in the Salmon River Basin in central Idaho that highlight the influence of topography and climatic variability within a large river basin on the runoff character. Study tributaries are grouped into three precipitation regimes that were selected using hypsometry. High elevation (2500 - 3200 m) study catchments are dominated by snow and have smooth, broad hydrographs. Mid elevation (1500 - 2200 m) basins span elevations that receive both snow and rain. These hydrographs reflect characteristics of both snowmelt and rainfall runoff. Liquid precipitation dominates lower elevation catchments (400 -1500), with flashier hydrographs that exhibit low baseflows. The unique behavior of tributaries within different precipitation zones is further revealed by the temporal separation of peak flows within respective elevation/precipitation zones; peak runoff becomes progressively later with increasing elevation and the proportion of snow to rain. Data from our monitoring sites suggest that environmental lapse rate is a first order control on precipitation and that the characteristics of runoff within a given zone is largely controlled by the range of elevations that comprise the catchment. Hydrologic analysis of USGS gages along the mainstem Salmon demonstrate that more water is delivered per unit area from high elevation catchments located on the western edge of the Salmon River basin. This suggests that there is a strong orographical forced precipitation gradient in a west to east direction and demonstrates that discharge does not scale linearly with drainage area in the Salmon River basin. This analysis provides physically based measurements that 1) highlight the hydrologic heterogeneity present within a large river basin, 2) provide insights about the potential hydrologic evolution of watersheds if snowlines rise by utilizing a space for time substitution, 3) provide an elegant mechanism for understanding the topographic sensitivity of a basin to rising snowlines (hypsometry) and 4) challenge well established theoretical hydrologic scaling relationships.

https://digitalcommons.usu.edu/runoff/2010/AllAbstracts/6