JAWRA - Stormwater Runoff

• Project Type: General OWC
• Title: Stormwater Runoff Quality and Quantity from Traditional & Low Impact Development Watersheds
• Date: 12/15/2009
• Water Conservation - Doc Type: Reports

STORMWATER RUNOFF QUALITY AND QUANTITY FROM TRADITIONAL AND LOW IMPACT DEVELOPMENT WATERSHEDS
TABLE 4. Mean Predicted and Observed Values and Percent Change From the LID and Control Watersheds
During the Calibration and Postconstruction Periods for the Jordan Cove Project, Connecticut.
Calibration Period Postconstruction Period (n = 75)
(n = 90)
LID
Characteristic Control LID Control Observed Predicted
ANCOVA
Calibration
Equation % Change F p
Storm flow (cm /week)
0.21
0.17
0.40
0.13
0.22
T = 0.407C 674
-42 * **
17.77
<0.001
Peak discharge
0.0360
0.0057
0.0262
0.0030
0.0041
T = 0.147C° 279
- 26N.s.
5.91
0.001
(m /s /week)
NO -N (mg /1)
0.5
0.2
1.3
0.4
0.2
T = 0.201C -0.106
+100*
3.33
0.021
NH -N (mgA)
0.20
0.05
0.14
0.03
0.06
T = 0.089C
-50*
8.61
<0.001
TKN (mg /1)
1.3
0.9
1.2
1.3
0.9
T = 0.816C
+44 **
20.37
<0.001
TP (mg /1)
0.139
0.027
0.165
0.291
0.028
T = 0.052C° 349
+939 * **
50.71
<0.001
TSS (mg /1)
29
4
24
11
4
T = 1.862C° 22
+197 * **
10.60
<0.001
BOD (mg /1)
2.9
2.9
3.1
3.3
3.4
T = 1.535C 705
-3 N-s.
9.72
<0.001
Fecal coliform
10
62
305
41
790
T = 17.091C 67
-95 **
5.57
0.006
(No /100 ml)
Cu (1tg 11)
10
8
10
6
8
T = 6.116C 12
-25 N.S.
0.96
0.419
Pb (pg /1)
6
4
2
1
3
T= 2.674C
-67 * **
10.05
<0.001
Zn (µg 11)
69
88
40
17
74
T = 18.146C° 38
-77 * **
9.63
<0.001
NO -N (kg /ha /year)
0.55
0.18
4.02
0.25
0.34
T = 1.99C° 271
_26N.s.
5.49
0.001
NH -N (kg /ha /year)
0.23
0.05
0.43
0.02
0.08
T = 1.034C° 183
-71 * **
9.26
<0.001
TKN (kg/ha/year)
1.59
0.73
3.99
0.90
1.36
T = 2.006C
-33*
16.67
<0.001
TP (kg/ha/year)
0.17
0.04
0.52
0.21
0.06
T = 0.404C
+249 **
23.83
<0.001
TSS (kg /ha/year)
35
3
75
8
5
T = 4.96C
+85*
20.28
<0.001
Cu (g /ha/year)
13
6
21
4
7
T = 10.862CO535
_50N.s.
2.03
0.122
Pb (g /ha /year)
7
3
5
0.5
2
T = 46.016C 234
-79 **
5.41
0.003
Zn (g /ha /year)
85
65
87
10
56
T = 0.435C
-81 **
7.65
<0.001
Fecal coliform
56
1,893
2,713
39
521
T = 6,061,917C° 125
-99 **
3.78
0.032
(No /ha /year x 10
Notes: C = control; N.S. = not significant; T = treatment.
In = number of samples; n for FC and metals were 20 and 28, respectively.
2n for FC and metals were 7 and 20, respectively.
*p < 0.05.
* *p < 0.01.
* * *p < 0.001.
Peak Discharge - Qp
10
1
3
E 0.1
r 0.01
N
d
�
Calibration
0.001
0
J
0.0001
0.00001
0.0oom 4-
0.001
0.01 0.1 1 10
Control Watershed (cm /wk)
FIGURE 4. Paired Storm Flow From the LID and Control
Watersheds During the Calibration and Postconstruction
Periods for the Jordan Cove Project, Connecticut.
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l p�� 0 0
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• • • Calibration
• O Treatment
Traditional Watershed. Mean peak discharge
from the traditional watershed increased by 30 times
when compared with values predicted by the calibra-
tion equation (Table 3). The increase in peak dis-
charge was likely due to the stormwater drainage
system and the impervious asphalt road. Urban land
use has been widely reported to increase peak dis-
charge when compared with nonurbanized areas
(Leopold, 1968; Schueler, 1994). One study, using a
rainfall- runoff model (DR3M), concluded that 25%
imperviousness led to a 54% increase in peak dis-
charge (Sloto, 1989). Another study in Georgia
reported that a watershed, more than half urbanized,
had peak discharges that were 30 -100% greater than
watersheds with 13% or less urbanization (Rose and
Peters, 2001).
Low Impact Development Watershed. Peak
discharge from the LID watershed decreased during
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 1003 JAWRA