PROJ01918 ‎(2)‎

• Contract/PO #: FS0077FX
• Contract Type: Grant
• Water District: 0
• Loan Projects - Doc Type: Feasibility Study

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for the period under consideration. Statistical analysis of historic data demonstrates that Surface
Creek data can be used to estimate monthly runoff at Leroux Creek.

Table 3
Monthly Runoff for Surface Creek (Gauge 1430) in ac-ft

Month 1 2 3 4 5 6 7 8 9 10 11 12 Annual
Mean 307 281 431 2,017 7,783 8,141 4,707 3,340 2,024 1,067 451 329 30,884
Percent 1.0 0.9 1.4 6.5 25.2 26.4 15.2 10.8 6.6 3.5 1.5 1.1 100.0
STD 147 125 219 1,112 3,041 4,346 2,000 973 688 493 292 177 10,144

The average annual runoff from Surface Creek is 92 percent of that of Leroux Creek. Runoff
during May and June is about 25 percent and 26 percent of annual runoff, respectively. This is a
variation from Leroux Creek and is likely the result of the orientation of the slopes in the basin of
Surface Creek. Even though there are monthly variations, total annual runoff in the two creeks
correlate well. The mean monthly runoff for each of the two creeks is shown on Figure 2.

Figure 2
Mean Monthly Runoff for Surface Creek and Leroux Creek

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The estimation of missing monthly runoff at Leroux Creek was performed using the same widely
accepted statistical methods used in the previous studies as summarized below:

.

Estimate the missing annual runoff at Leroux Creek using annual runoff data at Surface
Creek.

Distribute the estimated annual runoff over the months of the year using the percentages
of annual flow for Leroux Creek calculated from historic runoff data.

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