1. A small stream has flow data for April as shown in the table:
|
Date
|
Q (cfs)
|
Date
|
Q (cfs)
|
Date
|
Q (cfs)
|
Date
|
Q (cfs)
|
Date
|
0 (cfs)
|
|
1-Apr
|
248
|
7-Apr
|
254
|
13-Apr
|
725
|
19-Apr
|
215
|
25-Apr
|
216
|
|
2-Apr
|
359
|
8-Apr
|
596
|
14-Apr
|
548
|
20-Apr
|
548
|
26-Apr
|
843
|
|
3-Apr
|
154
|
9-Apr
|
357
|
15-Apr
|
921
|
21-Apr
|
265
|
27-Apr
|
845
|
|
4-Apr
|
856
|
10-Apr
|
248
|
16-Apr
|
325
|
22-Apr
|
157
|
28-Apr
|
365
|
|
5-Apr
|
92
|
11-Apr
|
368
|
17-Apr
|
365
|
23-Apr
|
920
|
29-Apr
|
282
|
|
6-Apr
|
487
|
12-Apr
|
954
|
18-Apr
|
219
|
24-Apr
|
215 _
|
30-Apr
|
204
|
Analyze this data set and discuss the following:
Raw Data Assessment
(a) Were there any outliers that you discarded? Which ones & Why
(b) Is there a trend to this data?
(c) What is the mean, median, and mode of this data set?
Ans: Mean = 438, Median = 358, Mode = 248
(d) What is its standard deviation of this data set? What are the upper and lower values of 67% range of the flows and how do these compare to the upper and lower values of the full range of data?
Ans: Std.Dev = 265, Range 174 - 703
(e) What is its Skewness, Standard Error of Skewness, and acceptability of the skewness of this data set?
Ans: Skedness 0.80, ses = 0.45
(f) What is its Kurtosis, Standard Error of Kurtosis, and acceptability of the Kurtosis of this data set?
Ans: Kertosis = -0.78, sek = 0.89
(g) Can a standard (Gaussian) distribution be used to describe this data set?
|
Probability of Exceedance
-- Construct the ranked exceedance graph of this data ---
(h) What is the best-fit trend line for the exceedance curve?
(1) What is the Correlation Coefficient (R2) for this trend line?
|
Ans: y=1.466e4003 Ans: R2 = 0.9203
|
(.1) If this stream floods the area when Q > 800 cfs. what is the probability that it will flood in January? What is the return period (T) of a flow rate of this stream being equal to or greater than 800 cfs in January? Ans: P = 97.8&. T = 1.02/yr
(k) To be a dependable water source for a small town, this stream must have a 95% probability of providing 135 cfs or greater during a typical January. Is this stream a good water source for this town?