to increase more rapidly at 50 hours, reaches a maximum of 28.63 m3/s at 84 hours, and then de-
creases until the end of the simulation. The peak of this hydrograph is larger than the peak of the
hydrograph in Figure 7. The hydrographs in Figures 7 and 8 differ because the suburban watershed
infiltrates less water than the agricultural watershed and consequently produces more runoff and less
subsurface and baseflow than the forested watershed.
TECHNICAL DESCRIPTION OF SNOMLT
SNOMLT is the sector in Object-GAWSER that calculates the average snow depth in a watershed.
SNOMLT is further subdivided into a "Hydrology" section and a "Density / Depth" section. The
Hydrology section calculates the water budget for the snowpack and the Density/Depth section cal-
culates the density and depth of the snowpack. The inputs to SNOMLT are rain, snow, and air tem-
perature. The outputs from SNOMLT are sublimation and meltwater.
Hydrology section
The Hydrology section calculates the water budget for the snowpack by tracking the solid and
liquid water content of the snowpack. To calculate the water budget, the Hydrology section considers
the melting, refreezing, sublimation, snowfall and rainfall associated with snowpack. In addition, the
Hydrology section calculates the liquid water released from snowpack when the liquid water content
of the snowpack exceeds the liquid water holding capacity of the snowpack.
Table 3. Variables and initial conditions for the hydrology sector.
Initial
Variable
Description
condition
Units
EXCESS_LWC
excess liquid water
0
mm of H2O
HOURS
time interval
0
h
mm/h-C
KF
the refreeze factor
0.21
mm/h-C
KMa
the adjusted melt factor
0.21
LWC
liquid water content of snowpack
0
mm of H2O
LWCAP
liquid water holding capacity of snowpack
12.68
mm of H2O
MELTP
potential melt
0
mm of water
POR
porosity of snowpack
0.78
vol/vol
RAINs
rain
0
mm of H2O/h
RAIN_IN _I
original rain input
0
mm of H2O/h
RAIN_IN_II
alternative rain input
0
mm of H2O/h
REFREZ
refrozen liquid water
0
mm of H20/h
REFREZP
potential refreeze
0.08
mm of H2O/h
SNOWs
new snow
0
mm of depth/h
SNOWE
solid water content of new snow
0
mm of H2O/h
SUBLM
actual rate of sublimation
0
mm of H2O/h
SWC
solid water content of snowpack
46.8
mm of water
C
TBAS
temperature of the snowpack
0
C
TEMPs
air temperature
4.01
C
TEMPSWITCH
temperature switch
0
TOT_LIQ_WTR_REL
total liquid water released from the snowpack
0
mm of H2O
The name, brief description, initial conditions, and the units of each variable in the Hydrology
section are shown in Table 3. The initial conditions for all the variables within the Hydrology section
except EXCESS_LWC, MELT_I, MELT_II, REFREZ, RAIN_IN_I, RAIN_IN_II, SNOWE, SUB-
LM, and TOT_LIQ_WTR_REL were taken from a technical memorandum prepared by H. Schroet-
er.* TOT_LIQ_WTR_REL is initially set to zero because it considers liquid water that has not yet
been generated by Object-GAWSER. EXCESS_LWC, MELT_I, MELT_II, RAIN_IN_I, and
* Personal communication with H. Schroeter, Schroeter and Associates, 1995.
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