Canopy interception storage

The canopy interception is a seperate storage on the leaves of the vegetation. If the LAI is zero, then the canopy interception will be zero, as will all of the items in this storage.

The items listed in Table 6.2 are those found in the “Canopy Interception component” water balance output in the water balance configuration file:

[WblTypeDefinition]

Name = 'CI'

DisplayName = 'Canopy Interception component'

Description = 'Canopy Interception component waterbalance items'

NoGroups = 5

Group = 'Precip(ci.qpad)'

Group = 'Can. ThroughFall(-ci.qpnet)'

Group = 'Evaporation(ci.qeint)'

Group = 'Can.Stor.Change(ci.dintsto)'

Group = 'Error(ci.ciwblerr)'

EndSect // WblTypeDefinition

The sign convention in the water balance is such that precipitation is negative (inflow) and evaporation is positive (outflow). All of the items together should add to zero.

Note, however, the negative sign in front of the ci.qpnet term in the water balance definition above. This is because the canopy throughfall is a vertical downward flow in MIKE SHE - making it a negative value in the MIKE SHE results files. Whereas, it must be a positive outflow in the water balance calculation.

Table 6.2 CI - Canopy interception water balance items
Item	Description	Sign Convention in the Water balance	Included in Wbl Error
ci.qPad	Total precipitation reaching the canopy (Precipitation + sprinkler irrigation + snowmelt to OL - precipitation converted to snow)	Inflow - negative	yes
-ci.qPnet	Canopy throughfall to ponded water	Outflow - positive (Note sign change in water balance definition)	yes
ci.qEInt	Evaporation from intercepted storage	Outflow - positive	yes
ci.dIntSto	Change in interception storage	Positive when interception storage increases	yes
ci.ciWblErr	Interception storage water balance error	Positive if water generated (Dstorage + Outflow > Inflow)