Snow Storage
The snow storage items include all of the water balance items related to rainfall and the conversion to and from snow.
The items listed in Table 6.1 are those found in the “Snow Melt component - detailed” water balance output in the water balance configuration file:
[WblTypeDefinition]
Name = 'SM_DETAIL'
DisplayName = 'Snow Melt component - detailed'
Description = 'Detailed Snow Melt component water balance'
NoGroups = 11
Group = 'Precip and Irr -> Snow(sm.qprecandirrtosnow)'
Group = 'AirTemp Freezing(sm.qfreezing)'
Group = 'AirTemp Melting(sm.qthawing)'
Group = 'Radiation Melting(sm.qradmelting)'
Group = 'Rain Melting(sm.qrainmelting)'
Group = 'Snow -> OL(sm.qsnowtool)'
Group = 'Snow Evap(sm.qesnow)'
Group = 'Dry Snow Stor.Change(sm.dsnowsto-sm.dwetsnowsto)'
Group = 'Wet Snow Stor.Change(sm.dwetsnowsto)'
Group = 'Total Snow Stor.Change(sm.dsnowsto)'
Group = 'Error(sm.smwblerr)'
EndSect // WblTypeDefinition
The sign convention is such that precipitation is negative (inflow) and melting is positive (outflow). All of the noted tems together should add to zero. The freezing and thawing items are not included in the error term because they are internal transfers of water between dry snow and wet snow storages.
The snow storage items are found in the projectname_sm.wblgross file. This file also contains the terms sm.qP, sm.qPad, and sm.PIrrSprinkler, which are not included in the detailed water balance output because they are included in the term sm.qPrecAndIrrToSnow.
Table 6.1 SM - Precipitation and snowmelt items
|
Item
|
Description
|
Sign Convention in the Water balance
|
Included in Wbl Error
|
|
sm.qPrecAndIrrToSnow
|
Precipitation plus irrigation added to snow storage when the air temperature is below the freezing temperature
|
Inflow - negative
|
yes
|
|
sm.qFreezing
|
Amount of wet snow converted to dry snow due to freezing
|
Negative
|
no
|
|
sm.qThawing
|
Amount of water removed from dry snow storage due to temperature melting
|
Positive when melting occurs
|
no
|
|
sm.qRadMelting
|
Amount of water removed from dry snow storage due to radiation melting
|
Positive when melting occurs
|
no
|
|
sm.qRainMelting
|
Amount of water removed from dry snow storage due to melting from rain
|
Positive when melting occurs
|
no
|
|
sm.qSnowToOL
|
Amount of wet snow storage transfered to interception storage.
Actually, this amount is added to qPad, which is the input to canopy interception. Then the water is added to ponded water via interception throughfall.
Note: Freezing of ponded water to snow storage is not accounted for in MIKE SHE
|
Outflow - positive when water is added to canopy interception
|
yes
|
|
sm.qESnow
|
Amount of evaporation from snow. This is a combination of sublimation from dry snow and evaporation from wet snow.
Evaporation is removed first from wet snow storage. When wet snow storage is zero, then sublimation from dry snow is removed because of the higher energy required for sublimation.
|
Outflow - positive when evaporation/sublimation occurs
|
yes
|
|
sm.dWetSnowSto
|
Change in wet snow storage
|
Positive when wet snow storage increases
|
no
|
|
sm.dSnowSto
|
Change in total snow storage
Note: Change in dry snow storage is (dSnowSto - dWetSnowSto)
|
Positive when total snow storage increases
|
yes
|
|
sm.smWblErr
|
Snow storage water balance error. Sum of marked items.
|
Positive if water generated (Dstorage + Outflow > Inflow)
|
|
|
sm.qP
|
Total precipitation
(not used in detailed SM WB output)
|
Inflow - negative
|
no
|
|
sm.qIrrSpinkler
|
Total Irrigation
(not used in detailed SM WB output)
|
Inflow - negative
|
no
|
|
sm.qPad
|
Total precipitation reaching the canopy (Precipitation + sprinkler irrigation + snowmelt to ponded water). Same as ci.qPad.
(not used in detailed SM WB output)
|
Outflow - positive
|
no
|
