watershed that is completely snow-covered, enter a value of zero. To simulate a watershed with no
snow cover, enter a value of one. To simulate a watershed with patchy snow cover, enter a value
between zero and one.
maps or from a geographic information system (GIS).
EDAY (mm/day) is the constant daily evaporation rate. EDAY is used to calculate the amount of
water evaporated off the watershed. Please note that EDAY is ignored by Object-GAWSER when
any snow cover is present or when rain is falling.
FCS, FD, FDs, FIMC_I, FIMC_II, FKEFF, FKMF, FKO, FKSS, FRAIN, FSAV, FSNOW, and
FTEMP are the adjustment factors described:
FCS adjusts the maximum seepage rate
FD adjusts the maximum percolation rate
FDs adjusts depression storage
FIMC_I adjusts the initial moisture content of the top layer of soil
FIMC_II adjusts the initial moisture content of the bottom layer of soil
FKEFF adjusts the hydraulic conductivity of the top layer of soil
FKMF adjusts the rate of melting and refreezing in the snowpack
FKO adjusts the rate of runoff
FKSS adjusts the rate of subsurface flow
FRAIN adjusts the rainfall rate, FSAV adjusts the rate of infiltration
FSNOW adjusts the snowfall rate, and FTEMP adjusts the air temperature.
Adjustment factors increase or dampen the effect of those hydrologic processes simulated by
Object-GAWSER, because they adjust the values of the input parameters that govern the rates of the
hydrologic processes. To increase the effect of a hydrologic process, the corresponding adjustment
factor should be programmed with a value greater than one. To dampen the effect of a hydrologic
process, the corresponding adjustment factor should be programmed with a value between zero and
one. To maintain the current effect of the hydrologic process, the corresponding adjustment factor
should be programmed with a value of one. For example, if you wanted to decrease the amount of
seepage into the bottom soil layer by 80%, you would set FCS to 0.8. Table 1 shows the adjustment
factor, the current value of the adjustment factor, and the input parameter whose set value is modified
by the adjustment factor.
INIT_STOR (mm) is the initial amount of water
Table 1. Description of the adjustment
in depression storage on the soil surface. INIT_
factors.
STOR applies to all GROFF sectors except
Adjustment
Corresponding
GROFF1, because GROFF1 simulates impervious
Adjustment
factor
input
surfaces (like paved areas) and GROFF2 GROFF5
factor
value
parameter(s)
simulate pervious surfaces. To simulate a watershed
FCS
1
CSs, CSs_2
with a dry soil surface, set INIT_STOR to zero. To
FD
1
Ds, Ds_2
simulate depression storage with some amount of
FDs
1
DS_IMPs, DSs, DSs_2
existing water, set INIT_STOR greater than zero and
FIMC_I
1.6
IMC_Is, IMC_Is _2
FIMC_II
1
IMC_IIs, IMC_IIs_2
less than the maximum depth of depression storage
FKEFF
1
KEFFs, KEFFs 2
(DSs for GROFF2 and GROFF3 and DSs_2 for
FKMF
0.5
KMs
GROFF4 and GROFF5). If the value of INIT_STOR
FKO
1.5
KOs
FKSS
1
KSSs
exceeds the value of maximum specified depth of
FRAIN
1
RAINs
depression storage, Object-GAWSER converts the
FSAV
1
SAVs
excess water to runoff.
FSNOW
1
SNOWs
FTEMP
1
TEMPs
NZONE (unitless) determines the number of
This table shows the adjustment factor, the current
zones used to model a given watershed. Set NZONE
value of the adjustment factor, and the names of the
equal to one to simulate a completely impervious
objects whose values are modulated by the adjust-
watershed. If NZONE is set to one, PCT_1 must also
ment factor.
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