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The hydrologic effects of urban land use: A case study of the little Miami River Basin
L,andscape and Urban Planning, 19 ( 1990) 99-l 05 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
99
Short Communication
The Hydrologic Effects of Urban Land Use: A Case Study of the Little Miami River Basin
SUSANNA T.Y.TONG Geography Department, University of Cincinnati, Cincinnati, OH 45221-0131 (U.S.A.) (Accepted for publication 22 August 1989)
.QBSTRACT Tong, S. T. Y., 1990. The hydrologic effects of urban land use: a case study of the Little Miami River Basin. Landscape Urban Plann., 19: 99-105. This paper examines the impacts of urbanization on the Little Miami River Basin. Flood ,frequencies of an urbanizing town (Milford) and a rural area (Perintown) were analyzed based
on the historical discharge data. Water samples were collected for chemical analyses and bioassays were conducted to determine the effects of runoff on seed germination and root development. The results of this study indicate that watershed urbanization has caused more frequent floods, poorer water quality and vegetation growth.
INTRODUCTION Watershed urbanization greatly alters the watercourses. The low vegetation density and the extensive impermeable surfaces reduce the infiltration capacity. Precipitation collected by rooftops and roads is diverted through the drainage systems into the nearby streams. Consequently, there is an increase in the volume of flood flows and the rate of runoff immediately downstream of the urban area. Studies by Hall ( 1984) and others reported more frequent floods in urban areas than in undeveloped ones. Apart from the change in discharge quantity, urbanization also affects water quality. 0169-2046/90/$03.50
0 1990 Elsevier Science Publishers B.V.
The influx of pollutants is partly caused by anthropogenic activities and partly by the accelerated denudation as flood characteristics are modified by urbanization. Roadside dust is inevitably contaminated which, when scavenged by rain and snowfall, will constitute a sizeable pollutant yield. Studies in major metropolitan areas revealed that urban runoff is a potent source of water pollution (see e.g. Pitt and Bozeman, 1980). The abrupt outfall of toxic and oxygen-demanding substances during storm events can cause temporary but drastic water quality changes, destroying recreation and aesthetics, and threatening biotic communities. The objective of this study was to examine
100
the consequences of urban development flood frequency and water quality.
on
STUDY AREA Little Miami River is a major tributary of the Ohio River. Its watershed covers an area of 5840 km2 with shale, limestone and dolomite (Upper Ordovician or Silurian ) parent materials. Most of the soils belong to the GeneseeWilliamsburg Association. The annual precipitation of the area averages 1050 mm and the river basin is subject to frequent flooding. Hydrological monitoring of the river by the United States Geological Survey (USGS) commenced in the 1925 water year. Based on the availability of the hydrological data, Milford and Perintown were selected for study. Both areas are located at the lower reach of the river, - 6.5 km apart, close enough to expedite field sampling. Milford is an urbanizing town and is 160 km east of Cincinnati. The close proximity to a metropolitan area, the lower land prices and the good accessibility made Milford a desirable location for urban development. Since 19 15, its population has increased more than four fold (from 1525 to 6240) and the greatest population growth occurred after 1965. Most of the original forest communities have been cleared and more and more farmland and pasture have been converted to residential and commercial uses. Conversely, Perintown is a small village and its population has remained roughly the same for the last six decades. The 1985 population was estimated to be < 1000. METHODS One of the primary tools to study the effects of urbanization on flood flows is the regional flood frequency method which relates flood magnitudes to their frequency of occurrence ( Dunn and Leopold, 1978 ). In this study, flood frequency curves for Milford and Perintown for the periods 1925-l 944, 1945-l 964 and 1965-
1984 were prepared. They represent the rural, early urban and middle urban stages of Milford. For each period, the annual peak flow data were first abstracted from the USGS discharge records. They were then tabulated and ranked in the order of discharge magnitude. The recurrence interval (RI) for every storm was computed as (N+ 1 )/Al, where N is the number of years of record and M is the order of that flood. A discharge frequency curve was drawn by plotting RI against the discharge value of each storm on semi-log paper and estimating the best fitting regression line. The discharge values for floods expected to recur in 1.0, 1.5,2.0,2.5, 5.0, 10.0 and 100.0 years were then predicted from the regression equation and expressed as ratios to the mean annual flood, the flood magnitude expected to occur once in 2.33 years. These dimensionless quotients were finally plotted against RI to give the flood frequency curve. When curves of different periods were drawn on the same graph, it provided a quick method to compare flood frequencies in various time periods for that locality. Although a few organizations, e.g. the Ohio Environmental Protection Agency ( EPA ) , USGS and Ohio River Valley Water Sanitation Commission (ORSANCO ), have examined the chemical quality of the river, none has a complete record. Hence, this investigation of the influences of urbanization on water quality was based on the water samples collected from the field. Earlier studies in urban runoff revealed that summer and fall depositions are higher than those in winter and spring (Bennett and Linstedt, 1978 ). Other workers, notably Weibel et al. ( 1964)) also reported that the first few millimeters of the runoff is most polluted. For these reasons, water samples were taken during fall in two periods: Periods D (dry, with no antecedent precipitation for the last 48 h, on October 7, 10 and 18, and November 2 and 29, 1986) and R (wet, at - 30 min after the storm had started, on October 1, 4 and 25, and November 5 and 25, 1986); as
101
HYDROLOGIC EFFECTS OF URBAN LAND USE
well as in three locations: Sites AM (0.5 km upstream from Milford), BM (0.5 km downstream of Milford ) and P (at Perintown ) . The notations of the sampling regimes are listed in Table 2. In each sample date/location, two samples were taken by grab samplers, each measuring 1000 ml. Altogether, there were 60 samples ( 10 sample dates, 3 locations, 2 replicates). The pH, conductivity, turbidity and temperature of the water were measured in the field, whereas dissolved oxygen (DO), biological oxygen demand ( BODS), hardness (as CaC03), chloride (Cl), phosphate (PO,), nitrate ( N03), iron (Fe) and lead (Pb ) were determined following the procedures outlined by the American Public Health Association (1985). The biological impact of urban runoff was also investigated. Germination tests were conducted on Brussica chinensis using the 60 water samples collected from the field. The cabbage is an ideal species for bioassays as it has a high germination rate and rapid root development (Tong and Wong, 1984). Sterilized petri dishes were lined with filter paper. Seeds were placed onto the dishes, 10 seeds per dish, and watered with 10 ml of test solutions. There were two controls with distilled water. All 62 sample plates were covered and placed inside a growth room at a temperature of 23-32 ‘C and a relative humidity of 50-70%. Daily germination counts and root length measurements were made to evaluate the germinability and seedling establishment. The test lasted for 3 weeks and, for each test regime, the root length results were averaged and the germination results were accumulated and expressed as percentages. “Germination value”, a product of the mean daily germination and peak value (Tong, 1987), was used as an index denoting the vigor and capacity for germination. RESULTS The discharge frequency regression equations for Milford and Perintown in different
TABLE 1 Regression equations for the discharge frequency curves for Milford and Perintown in 1925- 1944,1945- 1964 and 196% 1984. These equations were used to calculate the discharge values for floods expected to recur in 1.0, 1.5, 2.0, 2.33, 2.5, 5.0, 10.0 and 100.0 years Time period
Regression equation
Milford 1925-1944 1945-1964 1965-1984
Discharge= 7500+43 700 log (RI) Discharge= 10 000+47 000 log (RI) Discharge = 11 000 + 24 500 log (RI)
Perintown 1925-1944 1945-1964 1965-1984
Discharge=6900+ 18 100 log (RI) Discharge=8500+20 700 log (RI) Discharge= 3200+ 16 900 log (RI)
time periods are shown in Table 1. Based on these equations, the flood frequency curves were determined and the results are depicted in Figs. 1 and 2. At Milford, the ratio of mean annual flood for 1965-1984 was the highest and that for 1945- 1964 was slightly higher than that for 1925- 1944. These findings suggest that as the population increases, a higher frequency of floods with magnitude smaller than the mean annual flood will occur and urbanization has an appreciable impact on flood flows of a shorter recurrence interval than those of longer intervals. At Perintown, the ratio to mean annual flood was highest for the period of 19451964 and smallest for 1965-1984. Hence, in this case, no clear pattern of flood frequency increase with time was observed. Table 2 enlists the mean values of the water qualities for each sampling regime. In terms of BODS, P04, Fe, Pb, turbidity and hardness, the dry weather flow runoff was less contaminated than the wet weather flow. A better water quality in Perintown was also noted. While these findings might be attributable to local site-specific factors, further comparisons showed that the BMR samples taken downstream from Milford had higher levels of BODS, P04, Fe, Pb and turbidity than those of the AMR samples. Seemingly, the elevated levels of these elements in the vicinity of Milford (especially
102
RECURRENCE
Fig. I Flood 1984 ca--
frequency curves A ),Milford.
derived
from
three
0.2
periods
INTERVAL
of time:
I
(+ - - + ), 1945-1964
I
I
I
I
(O-
,
I
I
-0)
and
l965-
and
l965-
I10
RECURRENCE
Fig. 3. Flood frequency curves 1984 (A - - A ).Perintown.
TONG
(yr)
1925-1944
I
S.T.Y.
derived
from
three
periods
of time:
INTERVAL
1925-l
(yrl
944 ( + - - + ). 1945- I964
(0 - -0)
103
HYDROLOGIC EFFECTS OF URBAN LAND USE
TABLE 2 Average concentrations
of various water quality parameters
(mean of 10 samples)
Sampling regimes
Parameter (units)
AMR
BMR
15.6
15.0
16.1
9.40 6.04” 8.19 60.0
9.60 2.44 7.60 26.0
9.50 4.86b 8.00 76.0
9.61 6.45 8.10 78.0
0.12
0.13”
0.07
0.14b
0.16
0.10
0.40
0.90
1.10”
0.30
0.80
0.90
2.00-4.00
0.31
0.30”
0.36”
0.38
0.73b
1.10
0.30
0.05”
0.45
0.69”
0.13
0.51b
0.90
0.05
AMD
BMD
18.3
18.3
17.8
9.20 2.40 8.20” 35.0
9.39 4.44”b 8.20 57.Fb
0.05a
PD Temperature ( “C) DO BOD, J)H
(:llmgl-‘) PO:l:mgl-I) NO:(mgl-‘) Fez+
I:mg 1-l) Pb’+ (mg 1-l) IConductivity
390
(mohs) Turbidity (ntu) Hardness (mgl-‘)
740
0.2”
630
ll.8b
160a
16.0’
278”
280”
PR
E.P.A. drinking water standards*
350 1.8 180
710 12.0b 316
690 18.0 336
5.00 4.00 6.50-8.50 250.0
_ 30.0 250
PD=dry weather, at Perintown. AMD = dry weather, upstream from Milford. BMD=dry weather, downstream from Milford. PR = wet weather, at Perintown. 4MR = wet weather, upstream from Milford. BMR = wet weather, downstream from Milford. “Significant at P-c0.05 based on comparisons of the dry weather flow with the wet weather flow using Student’s t-test. bSignificant at PcO.05based on comparisons of the water samples collected upstream with those collected downstream Milford using Student’s t-test. *Kazmann ( 1972).
TABLE 3 The germination values of B. chinensis under different test regimes (control n = 20; other test regimes n = 100) Control
Test regimes
Germination value
AMD
BMD
PD
AMR
BMR
PR
321.30”
303.45’
267.75
233.24
214.20
237.96
‘Significant at P
249.90
with the Control using
from
downstream from the town) are ascribed to urban activities. In Milford, the concentrations of DO, BODS, P04, Fe, Pb and hardness were all above the E.P.A. drinking water standards; a result contrary to the findings of the State of Ohio Environmental Protection Agency ( 1986), but in agreement with Weibel et al. (1964). The germination values of B.chinensis cultured with the AMD and BMD water samples were relatively higher than those in the other test regimes (Table 3 ) . In general, samples collected during dry weather gave comparatively
104
3.5-
3.5.
3.0-
3.0-
2.5-
2.5-
0 0
2.0-
2.0-
E I !I
1.5.
1.5-
l.O-
l.O-
0.5-
0.5-
L P
/
O.OF 0
3
6
9
12
15
16
21
3
0
6
TIME PJavl
9 TI”E
12
15
16
21
Iday)
Fig. 3. Root development of B. chinensis cultured with distilled water ( o - - o ) and water samples collected during dry weather at Perintown (A - - - A ),upstream from Milford ( + - - + ) and downstream from Milford (O-.-.-O).
Fig. 4. Root tilled water wet weather ford (+ (O-.-.-O).
higher germination values. Apparently, seed germination is promoted by a higher level of nitrate and a lower metal concentration in the samples (see Table 2). In the root elongation experiment, the best test solution for root development was found to be PR, followed by PD and AMD (Figs. 3 and 4). Student’s t-test showed that root growth under each of these test regimes was significantly different from the control (PC 0.05 ). It is therefore evident that root development is more sensitive to water quality change and heavy metals can retard root growth. Hence, once the seeds are germinated, the chances for seedlings to establish are much higher in cleaner water, such as that collected at Perintown and upstream from Milford during dry weather.
tion has discernible impacts on flood regimes, water quality and vegetation growth. Thus, with the continual urbanization of Milford, an increase in flood frequency is anticipated. The potential of urban runoff, especially during the first-flush phenomena, to impair receiving water quality is also high. Localized degradation will result which may pose a significant threat to biological life.
This research was supported by a grant from the University Research Council of the University of Cincinnati. The author gratefully acknowledges the assistance of Marie Farrell, Jackie Gonima and James Dai in sample collection and data processing.
CONCLUSIONS
REFERENCES
Although banization,
American Public Health Association, 1985. Standard Methods for the Examination of Water and Wastewater. A.P.H.A., Washington, DC, 1268 pp.
Milford is in an early stage of urthis study confirms that urbaniza-
development of B. chinensis cultured with dis(o - - o ) and water samples collected during at Perintown ( A - - A ),upstream from Mil- + ) and downstream from Milford
ACKNOWLEDGMENTS
HYDROLOGIC
EFFECTS OF URBAN LAND USE
Bennett, E.R. and Linstedt, K.D., 1978. Pollutional Characteristics of Stormwater Runoff. Colo. Water Resour. Res. Inst. Complet. Rep. 84, Colorado State University, Colorado, 204 pp. Dunn, T. and Leopold, L.B., 1978. Water in Environmental Planning. Freeman, New York, 8 18 pp. Hall, M.J., 1984, Urban Hydrology. Elsevier, London/New York, 299 pp. Kazmann, R.G., 1972. Modern Hydrology. Harper and Row, New York, 365 pp. Pitt, R. and Bozeman, M., 1980. Water Quality and Biological Effects of Urban Runoff on Coyote Creek. EPA-600/ 2-80-104, U.S.E.P.A., Cincinnati, 73 pp.
105 State of Ohio Environmental Protection Agency, 1986. Little Miami River Comprehensive Water Quality Report, Ohio, 118~~. Tong, S.T.Y., 1987. The germination responses of Aristidu coerulescens, Helictotrichon filifolium and Helichrysum stoechas to temperature and water stress. Int. J. Ecol. Environ. Sci., 13: 133-147. Tong, S.T.Y. and Wong, M.H., 1984. Bioassay tests of landfill leachate using Brassica chinensis and Cynodon dactylon. Conservat. Recycl., 7: 283-294. Weibel, S.R., Anderson, R.J. and Woodward, R.L., 1964. Urban land runoff as a factor in stream pollution. Water Pollut. Control Fed., 36: 914-924.
99
Short Communication
The Hydrologic Effects of Urban Land Use: A Case Study of the Little Miami River Basin
SUSANNA T.Y.TONG Geography Department, University of Cincinnati, Cincinnati, OH 45221-0131 (U.S.A.) (Accepted for publication 22 August 1989)
.QBSTRACT Tong, S. T. Y., 1990. The hydrologic effects of urban land use: a case study of the Little Miami River Basin. Landscape Urban Plann., 19: 99-105. This paper examines the impacts of urbanization on the Little Miami River Basin. Flood ,frequencies of an urbanizing town (Milford) and a rural area (Perintown) were analyzed based
on the historical discharge data. Water samples were collected for chemical analyses and bioassays were conducted to determine the effects of runoff on seed germination and root development. The results of this study indicate that watershed urbanization has caused more frequent floods, poorer water quality and vegetation growth.
INTRODUCTION Watershed urbanization greatly alters the watercourses. The low vegetation density and the extensive impermeable surfaces reduce the infiltration capacity. Precipitation collected by rooftops and roads is diverted through the drainage systems into the nearby streams. Consequently, there is an increase in the volume of flood flows and the rate of runoff immediately downstream of the urban area. Studies by Hall ( 1984) and others reported more frequent floods in urban areas than in undeveloped ones. Apart from the change in discharge quantity, urbanization also affects water quality. 0169-2046/90/$03.50
0 1990 Elsevier Science Publishers B.V.
The influx of pollutants is partly caused by anthropogenic activities and partly by the accelerated denudation as flood characteristics are modified by urbanization. Roadside dust is inevitably contaminated which, when scavenged by rain and snowfall, will constitute a sizeable pollutant yield. Studies in major metropolitan areas revealed that urban runoff is a potent source of water pollution (see e.g. Pitt and Bozeman, 1980). The abrupt outfall of toxic and oxygen-demanding substances during storm events can cause temporary but drastic water quality changes, destroying recreation and aesthetics, and threatening biotic communities. The objective of this study was to examine
100
the consequences of urban development flood frequency and water quality.
on
STUDY AREA Little Miami River is a major tributary of the Ohio River. Its watershed covers an area of 5840 km2 with shale, limestone and dolomite (Upper Ordovician or Silurian ) parent materials. Most of the soils belong to the GeneseeWilliamsburg Association. The annual precipitation of the area averages 1050 mm and the river basin is subject to frequent flooding. Hydrological monitoring of the river by the United States Geological Survey (USGS) commenced in the 1925 water year. Based on the availability of the hydrological data, Milford and Perintown were selected for study. Both areas are located at the lower reach of the river, - 6.5 km apart, close enough to expedite field sampling. Milford is an urbanizing town and is 160 km east of Cincinnati. The close proximity to a metropolitan area, the lower land prices and the good accessibility made Milford a desirable location for urban development. Since 19 15, its population has increased more than four fold (from 1525 to 6240) and the greatest population growth occurred after 1965. Most of the original forest communities have been cleared and more and more farmland and pasture have been converted to residential and commercial uses. Conversely, Perintown is a small village and its population has remained roughly the same for the last six decades. The 1985 population was estimated to be < 1000. METHODS One of the primary tools to study the effects of urbanization on flood flows is the regional flood frequency method which relates flood magnitudes to their frequency of occurrence ( Dunn and Leopold, 1978 ). In this study, flood frequency curves for Milford and Perintown for the periods 1925-l 944, 1945-l 964 and 1965-
1984 were prepared. They represent the rural, early urban and middle urban stages of Milford. For each period, the annual peak flow data were first abstracted from the USGS discharge records. They were then tabulated and ranked in the order of discharge magnitude. The recurrence interval (RI) for every storm was computed as (N+ 1 )/Al, where N is the number of years of record and M is the order of that flood. A discharge frequency curve was drawn by plotting RI against the discharge value of each storm on semi-log paper and estimating the best fitting regression line. The discharge values for floods expected to recur in 1.0, 1.5,2.0,2.5, 5.0, 10.0 and 100.0 years were then predicted from the regression equation and expressed as ratios to the mean annual flood, the flood magnitude expected to occur once in 2.33 years. These dimensionless quotients were finally plotted against RI to give the flood frequency curve. When curves of different periods were drawn on the same graph, it provided a quick method to compare flood frequencies in various time periods for that locality. Although a few organizations, e.g. the Ohio Environmental Protection Agency ( EPA ) , USGS and Ohio River Valley Water Sanitation Commission (ORSANCO ), have examined the chemical quality of the river, none has a complete record. Hence, this investigation of the influences of urbanization on water quality was based on the water samples collected from the field. Earlier studies in urban runoff revealed that summer and fall depositions are higher than those in winter and spring (Bennett and Linstedt, 1978 ). Other workers, notably Weibel et al. ( 1964)) also reported that the first few millimeters of the runoff is most polluted. For these reasons, water samples were taken during fall in two periods: Periods D (dry, with no antecedent precipitation for the last 48 h, on October 7, 10 and 18, and November 2 and 29, 1986) and R (wet, at - 30 min after the storm had started, on October 1, 4 and 25, and November 5 and 25, 1986); as
101
HYDROLOGIC EFFECTS OF URBAN LAND USE
well as in three locations: Sites AM (0.5 km upstream from Milford), BM (0.5 km downstream of Milford ) and P (at Perintown ) . The notations of the sampling regimes are listed in Table 2. In each sample date/location, two samples were taken by grab samplers, each measuring 1000 ml. Altogether, there were 60 samples ( 10 sample dates, 3 locations, 2 replicates). The pH, conductivity, turbidity and temperature of the water were measured in the field, whereas dissolved oxygen (DO), biological oxygen demand ( BODS), hardness (as CaC03), chloride (Cl), phosphate (PO,), nitrate ( N03), iron (Fe) and lead (Pb ) were determined following the procedures outlined by the American Public Health Association (1985). The biological impact of urban runoff was also investigated. Germination tests were conducted on Brussica chinensis using the 60 water samples collected from the field. The cabbage is an ideal species for bioassays as it has a high germination rate and rapid root development (Tong and Wong, 1984). Sterilized petri dishes were lined with filter paper. Seeds were placed onto the dishes, 10 seeds per dish, and watered with 10 ml of test solutions. There were two controls with distilled water. All 62 sample plates were covered and placed inside a growth room at a temperature of 23-32 ‘C and a relative humidity of 50-70%. Daily germination counts and root length measurements were made to evaluate the germinability and seedling establishment. The test lasted for 3 weeks and, for each test regime, the root length results were averaged and the germination results were accumulated and expressed as percentages. “Germination value”, a product of the mean daily germination and peak value (Tong, 1987), was used as an index denoting the vigor and capacity for germination. RESULTS The discharge frequency regression equations for Milford and Perintown in different
TABLE 1 Regression equations for the discharge frequency curves for Milford and Perintown in 1925- 1944,1945- 1964 and 196% 1984. These equations were used to calculate the discharge values for floods expected to recur in 1.0, 1.5, 2.0, 2.33, 2.5, 5.0, 10.0 and 100.0 years Time period
Regression equation
Milford 1925-1944 1945-1964 1965-1984
Discharge= 7500+43 700 log (RI) Discharge= 10 000+47 000 log (RI) Discharge = 11 000 + 24 500 log (RI)
Perintown 1925-1944 1945-1964 1965-1984
Discharge=6900+ 18 100 log (RI) Discharge=8500+20 700 log (RI) Discharge= 3200+ 16 900 log (RI)
time periods are shown in Table 1. Based on these equations, the flood frequency curves were determined and the results are depicted in Figs. 1 and 2. At Milford, the ratio of mean annual flood for 1965-1984 was the highest and that for 1945- 1964 was slightly higher than that for 1925- 1944. These findings suggest that as the population increases, a higher frequency of floods with magnitude smaller than the mean annual flood will occur and urbanization has an appreciable impact on flood flows of a shorter recurrence interval than those of longer intervals. At Perintown, the ratio to mean annual flood was highest for the period of 19451964 and smallest for 1965-1984. Hence, in this case, no clear pattern of flood frequency increase with time was observed. Table 2 enlists the mean values of the water qualities for each sampling regime. In terms of BODS, P04, Fe, Pb, turbidity and hardness, the dry weather flow runoff was less contaminated than the wet weather flow. A better water quality in Perintown was also noted. While these findings might be attributable to local site-specific factors, further comparisons showed that the BMR samples taken downstream from Milford had higher levels of BODS, P04, Fe, Pb and turbidity than those of the AMR samples. Seemingly, the elevated levels of these elements in the vicinity of Milford (especially
102
RECURRENCE
Fig. I Flood 1984 ca--
frequency curves A ),Milford.
derived
from
three
0.2
periods
INTERVAL
of time:
I
(+ - - + ), 1945-1964
I
I
I
I
(O-
,
I
I
-0)
and
l965-
and
l965-
I10
RECURRENCE
Fig. 3. Flood frequency curves 1984 (A - - A ).Perintown.
TONG
(yr)
1925-1944
I
S.T.Y.
derived
from
three
periods
of time:
INTERVAL
1925-l
(yrl
944 ( + - - + ). 1945- I964
(0 - -0)
103
HYDROLOGIC EFFECTS OF URBAN LAND USE
TABLE 2 Average concentrations
of various water quality parameters
(mean of 10 samples)
Sampling regimes
Parameter (units)
AMR
BMR
15.6
15.0
16.1
9.40 6.04” 8.19 60.0
9.60 2.44 7.60 26.0
9.50 4.86b 8.00 76.0
9.61 6.45 8.10 78.0
0.12
0.13”
0.07
0.14b
0.16
0.10
0.40
0.90
1.10”
0.30
0.80
0.90
2.00-4.00
0.31
0.30”
0.36”
0.38
0.73b
1.10
0.30
0.05”
0.45
0.69”
0.13
0.51b
0.90
0.05
AMD
BMD
18.3
18.3
17.8
9.20 2.40 8.20” 35.0
9.39 4.44”b 8.20 57.Fb
0.05a
PD Temperature ( “C) DO BOD, J)H
(:llmgl-‘) PO:l:mgl-I) NO:(mgl-‘) Fez+
I:mg 1-l) Pb’+ (mg 1-l) IConductivity
390
(mohs) Turbidity (ntu) Hardness (mgl-‘)
740
0.2”
630
ll.8b
160a
16.0’
278”
280”
PR
E.P.A. drinking water standards*
350 1.8 180
710 12.0b 316
690 18.0 336
5.00 4.00 6.50-8.50 250.0
_ 30.0 250
PD=dry weather, at Perintown. AMD = dry weather, upstream from Milford. BMD=dry weather, downstream from Milford. PR = wet weather, at Perintown. 4MR = wet weather, upstream from Milford. BMR = wet weather, downstream from Milford. “Significant at P-c0.05 based on comparisons of the dry weather flow with the wet weather flow using Student’s t-test. bSignificant at PcO.05based on comparisons of the water samples collected upstream with those collected downstream Milford using Student’s t-test. *Kazmann ( 1972).
TABLE 3 The germination values of B. chinensis under different test regimes (control n = 20; other test regimes n = 100) Control
Test regimes
Germination value
AMD
BMD
PD
AMR
BMR
PR
321.30”
303.45’
267.75
233.24
214.20
237.96
‘Significant at P
249.90
with the Control using
from
downstream from the town) are ascribed to urban activities. In Milford, the concentrations of DO, BODS, P04, Fe, Pb and hardness were all above the E.P.A. drinking water standards; a result contrary to the findings of the State of Ohio Environmental Protection Agency ( 1986), but in agreement with Weibel et al. (1964). The germination values of B.chinensis cultured with the AMD and BMD water samples were relatively higher than those in the other test regimes (Table 3 ) . In general, samples collected during dry weather gave comparatively
104
3.5-
3.5.
3.0-
3.0-
2.5-
2.5-
0 0
2.0-
2.0-
E I !I
1.5.
1.5-
l.O-
l.O-
0.5-
0.5-
L P
/
O.OF 0
3
6
9
12
15
16
21
3
0
6
TIME PJavl
9 TI”E
12
15
16
21
Iday)
Fig. 3. Root development of B. chinensis cultured with distilled water ( o - - o ) and water samples collected during dry weather at Perintown (A - - - A ),upstream from Milford ( + - - + ) and downstream from Milford (O-.-.-O).
Fig. 4. Root tilled water wet weather ford (+ (O-.-.-O).
higher germination values. Apparently, seed germination is promoted by a higher level of nitrate and a lower metal concentration in the samples (see Table 2). In the root elongation experiment, the best test solution for root development was found to be PR, followed by PD and AMD (Figs. 3 and 4). Student’s t-test showed that root growth under each of these test regimes was significantly different from the control (PC 0.05 ). It is therefore evident that root development is more sensitive to water quality change and heavy metals can retard root growth. Hence, once the seeds are germinated, the chances for seedlings to establish are much higher in cleaner water, such as that collected at Perintown and upstream from Milford during dry weather.
tion has discernible impacts on flood regimes, water quality and vegetation growth. Thus, with the continual urbanization of Milford, an increase in flood frequency is anticipated. The potential of urban runoff, especially during the first-flush phenomena, to impair receiving water quality is also high. Localized degradation will result which may pose a significant threat to biological life.
This research was supported by a grant from the University Research Council of the University of Cincinnati. The author gratefully acknowledges the assistance of Marie Farrell, Jackie Gonima and James Dai in sample collection and data processing.
CONCLUSIONS
REFERENCES
Although banization,
American Public Health Association, 1985. Standard Methods for the Examination of Water and Wastewater. A.P.H.A., Washington, DC, 1268 pp.
Milford is in an early stage of urthis study confirms that urbaniza-
development of B. chinensis cultured with dis(o - - o ) and water samples collected during at Perintown ( A - - A ),upstream from Mil- + ) and downstream from Milford
ACKNOWLEDGMENTS
HYDROLOGIC
EFFECTS OF URBAN LAND USE
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