The variables and melt_min allow the rate of snow melt to vary through the year and account for the impact of snowpack density on snow melt.

If the watershed is in the Northern Hemisphere, melt_min will be the maximum melt factor. If the watershed is in the Southern Hemisphere, melt_min will be the minimum melt factor.

Mean air temperature at which precipitation is equally likely to be rain as snow/freezing rain.

The variables melt_max and allow the rate of snow melt to vary through the year and account for the impact of snowpack density on snow melt.

If the watershed is in the Northern Hemisphere, melt_max will be the maximum melt factor. If the watershed is in the Southern Hemisphere, melt_max will be the minimum melt factor.

The name of the snow record is a primary key referenced by in .

Due to factors such as drifting, shading, and topography, the snow pack in a HRU will rarely be uniformly distributed over the total area. A fraction of the HRU area will be bare of snow. This fraction must be quantified to accurately compute snow melt in the HRU.

The factors that contribute to variable snow coverage are usually similar from year to year, making it possible to correlate the areal coverage of snow with the amount of snow present in the HRU at a given time. This correlation is expressed as an areal depletion curve, which is used to describe the seasonal growth and recession of the snow pack as a function of the amount of snow present in the HRU.

The areal depletion curve requires a threshold depth of snow to be defined, above which there will always be 100% cover. The threshold depth will depend on factors such as vegetation distribution, wind loading of snow, wind scouring of snow, interception, and aspect and will be unique to the watershed of interest.

The influence of the previous day’s snowpack temperature on the current day’s snow pack temperature is controlled by a lagging factor, which inherently accounts for snow pack density, snowpack depth, exposure and other factors affecting snowpack temperature.

The snow pack will not melt until the snow pack temperature exceeds melt_tmp.

SWAT+ assumes a non-linear relationship between snow water and snow cover. This parameter defines the fraction of the snow volume represented by that corresponds to 50% snow cover.