ond delay of the lag and route structure. OUTFLOW_2_LAG should therefore peak after OUT-
FLOW_2. Figure 23 shows that the lag and route structure operates properly because INFLOW_2
peaks first, OUTFLOW_2 peaks second, and OUTFL_2_LAG peaks third. The smoothing effect
first shown in Figure 21 is also shown in Figure 22 by the difference between INFLOW_2 and
OUTFLOW_2. OUTFLOW_2 and OUTFL_2_LAG are equal in magnitude because there is no stor-
age of water as the water from OUTFLOW_2 is delayed and becomes OUTFLOW_2_LAG. The
difference in magnitude between OUTFLOW_2, OUTFL_2_LAG and INFLOW_2 is due to the
storage effect of LG_RT_STOR.
TECHNICAL DESCRIPTION OF CHNLRTNG
Channel routing is performed in the sector entitled "CHNLRTNG." The lagged values of runoff,
subsurface flow, and baseflow are summed together to represent the total discharge from the water-
shed outlet. The total discharge then enters a fictitious channel that begins at the watershed outlet.
Object-GAWSER routes the discharge from the watershed outlet through the fictitious channel using
the Muskingum technique (Nash 1959, Dooge 1973). The name, brief description, initial condition,
and units of each variable featured in this section are listed in Table 15.
Table 15. Explanation of the channel routing variables.
Initial
Variable
Description
condition
Units
m3/s
CHNL INFLW
inflow to channel segment
4.82
m3/s
CHNL OUTFLW
outflow from channel segment
10.1
m3 h/s
CHNL STOR
storage in channel segment
85.1
km2
DA
drainage area of the watershed
63
K
linear reservoir lag
10
h
m3/s
QBGW
initial subsurface base flow
2.59
m3/s
QBSS
Initial ground water base flow
0.863
m3/s
DISCHARGE
discharge from watershed
4.82
m3 h/s
QSUM
total discharge from watershed
8.51
m3/s
OUTFLOW_CLC
outflow calculation
10.09
m3/s
OUTFLOW_II
outflow from ground water or subsurface storage from zone 2
0.45
m3/s
OUTFLOW_III
outflow from ground water or subsurface storage from zone 3
0.07
m3/s
OUTFLOW_IV
outflow from ground water or subsurface storage from zone 4
0.24
m3/s
OUTFLOW_V
outflow from ground water or subsurface storage from zone 5
4.07
m3/s
SRF_RUNOFF
runoff
0.0
X
Muskingum (wedge storage) weighting coefficient
0.3
unitless
Initial conditions were derived in the following manner. DA is identical to DA on page 5-13 of the
GAWSER manual. K and X are identical to K and X from a modified version of Lesson 3 in the
GAWSER manual. CHNL_INFLW, CHNL_OUTFLW, DISCHARGE, OUTFLOW_II,
OUTFLOW_III, OUTFLOW_IV, OUTFLOW_V, OUTFLOW_CLC, and SRF_RUNOFF were de-
rived by Object-GAWSER. The initial value of QSUM is equal to the sum of QSS and QB.
CHNL_STOR is equal to the sum of QSS and QB multiplied by K. The units for CHNL STOR are
m3 h/s because it is incremented by m3/s and is calculated hourly. QSS is identical to QBSS on page
4-16 of the GAWSER manual. QB is identical to QBGW on page 4-16 of the GAWSER manual. The
units for QSUM are m3 h/s because QSUM is incremented by m3/s and is calculated hourly.
Figure 24 is the structural diagram for the entire channel routing sector (CHNLRTNG) which
contains the equations that perform channel routing. The discharge from the watershed outlet is
calculated with DISCHARGE, OUTFLOW_II, OUTFLOW_III, OUTFLOW_IV, QSUM, and
SRF_RUNOFF. The Muskingum method, which routes the discharge from the watershed outlet
along a fictitious channel segment, is calculated with CHNL_INFLW, CHNL_STOR,
CHNL_OUTFL, OUTFL_CALC, K, and X. QSS and QB are used to calculate both the discharge
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