C150094 Red Mesa Ward Hydrology Study

• Contract/PO #: C150094
• Contractor Name: La Plata Water Conservancy District
• Contract Type: Grant
• County: La Plata
• Loan Projects - Doc Type: Report

• 120
h 3/1-r�r ratios. The geographical distribution
with -g correlated with magnitudes of
of than storms Angeles and San Diego
the 16/1-h to 1-hr of fig also 4.7. Forvexample, Los Ang 0.60)
the 6/1-hr ratios of figure 4.7• (approximately(high 6/1-hr ratios) have low 15-mir. to 1-hr ratios ( pP
15-min to 1-hr ratios in Arizona and Utah (low 6/1-hr ratios)
were r
whereas generally higher her (approximately 0.75) .
for 1
ation relations for durations less than rehour were etthen smoothed
Depth-duration to some of the
to provide a family of curves consistent with was necessary
to 6 hours, as shown in figure 4.3. Adjustment
provide smoother relations through the common point at 1 hour.
curve s to P
justified in reducing the number of the curves shown in
We believe we were ] letting one curve apply to
range of 6/1-hr for durations less than corresponding curves have been indiccated amount
range of s/gna ratios. The come 4 3. As an example, for any
letter designators, A-D. on figure 2
between 1157 and 1352 of 1-hr, 1-mi2 (2.6-km ) s
"B" .
F . the associated values
less than 1 hour are obtained from the curve designated as
for durations pMP for selected
percent of 1-hr 4.3.
Table rain ratio durTheseavaluesaweresinterpolated from figure
6/1-hr rain ratios. or table 4.4) and the
To determine 6-hr Pte for a basin, use figure 4.3
geographical distribution of 6/1-hr ratios given in figure 4.7.
PM?4.4.--Durational variation of 1-m12 (2.6-km2)
in percent of 1-hr PMP (see figure 4.3)
Duration (hr) 4 5 6
ratio 3/4 1 2 3
1/4 1/2 110
ratio ' 110 110
93 97 100 107 109 119 120
1.2 86 95 100 110 115 118 130
74 89 114 121 125 128
1.2 89 95 100 137 140
1.3 74 118 126 132 150
63 83 93 100 121 132 140 145
1.4 83 93 100 147 154 160
1.6 63 87 100 124 138 180
1.6 43 70 130 149 161 171
43 70 87 100 137 161 175 188 200
1.8 70 87 100
2.0 43
4.5 Depth-Area Relation
(2.6 km2) ..
2 PMP should
We have thus far basin,developed local-storm edeterminef an PM based
To apply PMP to a basin, we need relat
decrease with increasing area. We have adopted depth-area
on rainfalls in
the Southwest and from consideration of a model thunderstorm.
to