CE 394K.2 Hydrology
Homework 6
Effect of Best Management Practices on Water Quality
Two Austin watersheds, Jollyville and Far West, have Best Management Practices that improve their water quality. Jollyville has a sand filter and Far West has an extended detention basin (has water ponded in it continuously). The purpose of this exercise is to determine how to compare one set of water quality data with another and see if there are significant differences between them. The attached spreadsheet WaterQuality.xls shows inflow and outflow data for storm events at these two facilities. In some cases, only inflow data or outflow data is shown, while in other cases, both are shown. Sometimes water quality sampling equipment fails to function. It would be ideal to compare inflow and outflow for the same events at the two watersheds but the data don’t support doing that for all events, so we’ll use a more general approach to defining the differences.
The data following show the inflow and outflow of Total Suspended Solids (TSS) measured in mg/liter, for various storm events whose date of occurrence is imbedded in the EventID field.
|
Jolleyville Sand
Filter |
Far West Pond |
|||||
|
TSS (MG/L) |
TSS (MG/L) |
|||||
|
EventID |
Inflow |
Outflow |
EventID |
Inflow |
Outflow |
|
|
19880520A |
|
136.92 |
19970617A |
99.54 |
|
|
|
19880529A |
990.12 |
34.55 |
19970807A |
100.11 |
139.74 |
|
|
19880601A |
204.19 |
25.39 |
19970922A |
|
157.28 |
|
|
19880602A |
422.99 |
21.81 |
19970922B |
135.95 |
|
|
|
19880602B |
230.69 |
|
19970923A |
|
203.58 |
|
|
19880811A |
269.11 |
288.03 |
19971007A |
107.18 |
|
|
|
19880930A |
122.86 |
|
19971008A |
56.96 |
|
|
|
19881031A |
52.68 |
16.61 |
19971009A |
70.98 |
|
|
|
19890129A |
151.81 |
|
19971219A |
65.00 |
|
|
|
19890328A |
668.27 |
|
19971220A |
|
22.87 |
|
|
19890413A |
138.94 |
10.85 |
19971220B |
64.65 |
|
|
|
19890419A |
13.70 |
19980106A |
76.19 |
30.15 |
||
|
19890505A |
121.75 |
6.20 |
19980131A |
40.34 |
48.30 |
|
|
19890510A |
120.04 |
7.89 |
19980214A |
72.08 |
38.37 |
|
|
19890513A |
135.35 |
2.31 |
19980221A |
135.16 |
53.69 |
|
|
19890516A |
145.00 |
|
19980225A |
|
49.31 |
|
|
19890517A |
122.34 |
|
19980330A |
99.80 |
64.67 |
|
|
19890520A |
111.26 |
|
19980704A |
213.34 |
|
|
|
19890611A |
909.11 |
40.96 |
19980910A |
85.56 |
|
|
|
19890613A |
258.62 |
17.30 |
19980911A |
|
14.67 |
|
|
19890801A |
29.35 |
mean |
94.86 |
74.79 |
||
|
19890815A |
658.64 |
41.21 |
std dev |
42.52 |
62.56 |
|
|
19891007A |
860.26 |
33.15 |
count |
15.00 |
11.00 |
|
|
19891030A |
396.65 |
|
std err |
10.98 |
18.86 |
|
|
19891122A |
227.71 |
24.86 |
Confidence |
31.03 |
18.06 |
|
|
19900218A |
139.95 |
6.39 |
||||
|
19900314A |
9.25 |
|||||
|
19900426A |
9.64 |
|||||
|
19900604A |
18.51 |
|||||
|
19941104A |
116.52 |
|
||||
|
19950112A |
3.00 |
|||||
|
19950312A |
142.26 |
|
||||
|
19950313A |
4.29 |
|||||
|
19950404A |
257.52 |
1.27 |
||||
|
19950405A |
146.56 |
|
||||
|
19950508A |
10.39 |
|||||
|
19950518A |
10.53 |
|||||
|
19950531A |
39.89 |
|
||||
|
19950611A |
68.51 |
9.38 |
||||
|
19950730A |
187.76 |
13.17 |
||||
|
19950731B |
1.31 |
|||||
|
19951117A |
146.26 |
2.94 |
||||
|
19960422A |
8.58 |
|||||
|
19970425A |
110.38 |
0.50 |
||||
|
19970426A |
107.78 |
0.25 |
||||
|
19970509A |
115.39 |
1.05 |
||||
|
mean |
261.68 |
25.34 |
||||
|
std dev |
253.39 |
52.31 |
||||
|
count |
34.00 |
34.00 |
||||
|
std err |
43.46 |
8.97 |
||||
|
Confidence |
71.48 |
14.76 |
||||
The Confidence function in Excel is here used with a = 0.10
A table of t-statistic values are shown below
Source: http://espse.educ.psu.edu/edpsych/faculty/rhale/statistics/Tables/tvalue.html
Assignment
Complete the table for the comparisons shown below for watersheds and BMP’s.
Watershed Comparison
|
Constituent |
Jollyville
Watershed |
Far West
Watershed |
Likelihood that the concentrations are
the same for the two watersheds (p value) |
|
Cd |
|
|
|
|
COD |
|
|
|
|
Cu |
|
|
|
|
Diss P |
|
|
|
|
Fecal Coliform |
|
|
|
|
Fecal Strep |
|
|
|
|
NH3 |
|
|
|
|
NO2+3 |
|
|
|
|
Pb |
|
|
|
|
TKN |
|
|
|
|
Total P |
|
|
|
|
TSS |
262 ± 71 |
95± 18 |
p<0.001
(not paired) |
|
VSS |
|
|
|
|
Zn |
|
|
|
Jollyville Sand
Filter Performance
|
Constituent |
Jollyville
Influent |
Jollyville
Effluent |
Likelihood that the concentrations are
the same (p value) (i.e., no reduction for this pollutant) |
|
Cd |
|
|
|
|
COD |
|
|
|
|
Cu |
|
|
|
|
Diss P |
|
|
|
|
Fecal Coliform |
|
|
|
|
Fecal Strep |
|
|
|
|
NH3 |
|
|
|
|
NO2+3 |
|
|
|
|
Pb |
|
|
|
|
TKN |
|
|
|
|
Total P |
|
|
|
|
TSS |
262 ± 71 |
25 ± 15 |
p <0.001 |
|
VSS |
|
|
|
|
Zn |
|
|
|
Far West Extended
Detention Basin Performance
|
Constituent |
Far West
Influent |
Far West
Effluent |
Likelihood that the concentrations are
the same (p value) (i.e., no reduction for this pollutant) |
|
Cd |
|
|
|
|
COD |
|
|
|
|
Cu |
|
|
|
|
Diss P |
|
|
|
|
Fecal Coliform |
|
|
|
|
Fecal Strep |
|
|
|
|
NH3 |
|
|
|
|
NO2+3 |
|
|
|
|
Pb |
|
|
|
|
TKN |
|
|
|
|
Total P |
|
|
|
|
TSS |
95± 18 |
75 ± 31 |
p = 0.21 (paired test) |
|
VSS |
|
|
|
|
Zn |
|
|
|