6. One paragraph description of your model (e.g. abstract from report 
   or paper);

In each model pixel, the land surface may be composed of overstory
vegetation, understory vegetation, and soil. The overstory may cover 
all or a prescribed fraction of the land surface. The understory, 
if present, covers the entire ground surface. The model allows land 
surface representations ranging from a closed two-story forest, to 
sparse low-lying natural vegetation or crops, to bare soil. 
Meteorological conditions (precipitation, air temperature, solar 
radiation, wind speed, vapor pressure) are prescribed at a specified 
reference height well above the overstory.  
	
Solar radiation and wind speed are attenuated through the two
canopies. If snow is present, it is assumed to cover the understory 
and thus affects radiation transfer and the wind profiles via increased 
albedo and decreased surface roughness. Temperature and relative 
humidity are not adjusted through the canopy.
	
An independent one-dimensional (vertical) water balance is calculated 
for each pixel (Wigmosta et al., 1994). Evaporation of intercepted 
water from the surfaces of wet vegetation is assumed to occur at 
the potential rate. Transpiration from dry vegetative surfaces is
calculated using a Penman-Monteith approach. The model follows 
Entekhabi and Eagleson (1989) in using a soil physics-based approach 
to calculate soil evaporation.  
	
Precipitation occurring below a threshold temperature is assumed
to be snow. Snow interception by the overstory is calculated as a
function of Leaf Area Index and is adjusted downward for windy or 
cold conditions (Schmidt and Troendle, 1992). Intercepted snow can 
be removed from the canopy through snow melt, sublimation, and mass 
release. Melt of intercepted snow is calculated based on a single 
layer energy balance approach. Mass release occurs if sufficient 
melt water is generated during an individual time step such that 
the snow slides off the canopy (Bunnell et al., 1985; Calder, 1990). 
Drip from the canopy is added to the ground snowpack (if present) 
as rain while the cold content of any mass release or unintercepted 
snow is added directly to the ground snowpack.  

Ground snow accumulation and melt are simulated using a two-layer
energy-balance model at the snow surface, similar to that described 
by Anderson (1968). The model accounts for the energy advected by 
rain, throughfall or drip, as well as net radiation and sensible and 
latent heat. Bulk transfer coefficients for turbulent exchange are 
calculated based on the aerodynamic resistance from the snow surface 
to the calculated two-meter wind and adjusted for atmospheric 
stability.

50. Please provide references relevant to the model description and use.

Wigmosta, M. S., D. P. Lettenmaier, and L. W. Vail, 1994, A distributed
hydrology-vegetation model for complex terrain, Water Resources Research,
30(6), 1665-1679.

Storck, P., D. P. Lettenmaier, B. A. Connelly, T. W. Cundy, 1995,
Implications of forest practices on downstream flooding: Phase II Final
Report, Washington Forest Protection Association, TFW-SH20-96-001, 100p.

Pascal Storck, Laura Bowling, Paul Wetherbee, Dennis Lettenmaier,
APPLICATION OF A GIS-BASED DISTRIBUTED HYDROLOGY MODEL FOR PREDICTION OF
FOREST HARVEST EFFECTS ON PEAK STREAMFLOW IN THE PACIFIC NORTHWEST,
Accepted for publication in a special issue of Hydrological processes.