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Streamflow Generation

Streamflow Generation. Streamflow generated by snowmelt water that directly runs off rather than infiltrating or from water that infiltrates and then moves downslope through a shallow subsurface soil of high permeability.

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Streamflow Generation

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  1. Streamflow Generation • Streamflow generated by snowmelt water that directly runs off rather than infiltrating or from water that infiltrates and then moves downslope through a shallow subsurface soil of high permeability. • During snowmelt, frozen or saturated soils restrict infiltration and evaporation is relatively low; this promotes a water excess over a basin and permits relatively large runoff generation for the amount of water applied to the ground.

  2. As a result, peak annual streamflows often occur directly after snowmelt. • The constituent water of this freshet comprise both snowmelt water and water expelled from soils by infiltrating snowmelt water, with important implications for stream chemistry. • For point scales, the influence of snow water equivalent on infiltration and runoff generation varies for different soil types.

  3. The effect of a deep forest environment snowpacks in promoting warm soils causes forest runoff to drop with increasing snow water equivalent for deep snow and dry soils. • In northern forests, from 40 to 60% of annual streamflow is derived from snowmelt, with increases in snowmelt runoff of from 24 to 75% when the forest is removed by harvesting or fire. • In cold, semiarid environments (arctic, northern prairies, steppes), greater than 80% of annual streamflow is derived from snowmelt, even though snowfall accounts for less than 50% of the annual precipitation.

  4. Snowmelt in the western cordillera of North America and mountain systems of central Asia is the major source of water when carried as streamflow to semiarid regions downstream. • Snowmelt water sustains arctic, alpine, prairie, and boreal forest lakes and wetlands, which are primary aquatic habitats in their respective ecosystems.

  5. Ref: Barnett et al. (2005)

  6. Source: Yang et al. (2003), JGR. Source: Déry et al. (2005), J. Climate. Annual Cycle of River Discharge

  7. Annual cycle of mean daily runoff Source: Déry et al. (2009), WRR.

  8. Latitudinal Variation of HJUB Freshets JD = 5(Latitude) -126 Source: Déry et al. (2005), J. Climate.

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