runoff

Author:

 Keith Cherkauer

Date:

 May 18, 1996

Description:

 This subroutine computes surface runoff, infiltration into the soil, and through the soil layers, and out the bottom as baseflow. Runoff is controlled by the Arno curve, which assumes that moisture in the top layer is not evenly distributed.

References:

Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, A Simple hydrologically Based Model of Land Surface Water and Energy Fluxes for GSMs, J. Geophys. Res., 99(D7), 14,415-14,428, 1994. 

Input Variables:

Variable

Type

Units

Description

 layer

layer_data_struct *

N/A

Structure contains soil layer variables

  • moist - unfrozen layer moisture content [mm]
  • moist_froz - frozen layer moisture content [mm]
  • moist_thaw - thawed layer moisture content [mm]
  • ice - frozen layer ice content [mm]
  • T - unfrozen layer temperature [C]
  • T_froz - frozen layer temperature [C]
  • T_thaw - thawed layer temperature [C]
  • tdepth - thaw depth in soil layer [m]
  • fdepth - frost depth in soil layer [m]
  • evap - layer evapotranspiration [mm]
  • unfrozen - maximum unfrozen water content in layer [mm]

soil_con

soil_con_struct

N/A

Structure contains soil parameters

  • Ksat - saturated hydraulic conductivity [mm/day]
  • depth - soil layer thickness [m]
  • max_moist - maximum soil layer moisture content [mm]
  • b_infilt - infiltration parameter [N/A]
  • expt - 2/Bp+3 where Bp is the pore-size distribution, exponent that controls drainage between layers, and unfrozen moisture content [N/A]
  • Dsmax - maximum baseflow rate [mm/day]
  • Ds - fraction of maximum baseflow rate above which flow is non-linear [fraction]
  • Ws - fraction of maximum soil moisture above which flow is non-linear [fraction]
  • c - baseflow exponent [N/A] (default 2)

mu

double

fraction

Fraction of grid cell that receives precipitation

x

double

fraction

Fraction of mu that receives precipitation that exceeds the interception capacity of the vegetation

ppt

double

mm

Total precipitation

dt

int

hr

Model time step

Tlayer

int

N/A

Total number of thermal solution nodes

 

Output Variables:

Variable

Type

Units

Description

 runoff

double *

mm

Runoff from grid cell

baseflow

double *

mm

Baseflow from grid cell

energy

energy_bal_struct *

N/A

Structure contains energy balance variables

  • kappa - thermal conductivity of soil layer [W/m/K]
  • Cs - volumetric heat capacity of soil layer [J/m3/K]

 layer

layer_data_struct *

N/A

Structure contains soil layer variables

  • moist - unfrozen layer moisture content [mm]
  • moist_froz - frozen layer moisture content [mm]
  • moist_thaw - thawed layer moisture content [mm]
  • ice - frozen layer ice content [mm]

 

Subroutines Called:

 

Modifications and Limitations:

 

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