Tech Memo Approval Form ATTACHMENT A

TECH MEMO USE
Document No.: 338884-PI-03-14
Revision No. 0
Effective Date: 10/17/2007
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ATTACHMENT A
Tech Memo Approval Form
Tech Memo Number: 338884-TMEM-090
Revision: 1
Project: 338884
Review Date: 1/28/09
Tech Memo Title: Historical Flow Data Analysis at Inglis Dam, Citrus County, Florida
Revision History:
Revision
Number
Description
Approval
Date
Affected Pages
0
Initial submittal for formal review.
1/29/09
All
Document Review and Approval
Originator:
Rich Srivastava
1/29/09
Name/Position
Date
Signature
Reviewer
Mitchell L. Griffin/Principal Technologist
1/29/09
Name/Position
Date
Signature
Project Manager:
Lorin Young/Project Manager
1/29/09
Name/Position
Approval
Date
Signature
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MEMORANDUM
Historical Flow Data Analysis at Inglis Dam, Citrus
County, Florida
1.
Introduction
The 3,400-acre Lake Rousseau was formed by the construction of Inglis Dam in 1909 by
Florida Power Corporation. Water from the Withlacoochee River is impounded by Inglis
dam, and then continues into the Gulf of Mexico. Although the dam was constructed for the
generation of hydroelectric power, hydropower operations ceased in 1965, when the U.S.
Army Corps of Engineers assumed operation and maintenance. The dam is now operated
only as a flood control structure.
In the 1960's, the Corps built a portion of the Cross Florida Barge Canal (CFBC) between
Lake Rousseau and the Gulf of Mexico. The barge canal bisected the Withlacoochee River
below Lake Rousseau, so that releases through the main spillway at Inglis Dam now flow
through an old segment of the river channel (Old Withlacoochee River, OWR) and then
enters the CFBC en route to the Gulf. Since construction of the CFBC interrupted the
natural flow of water from the upper into the lower segment of the river, the Corps
constructed the 8,900 foot long Inglis Lock Bypass channel (bypass channel) to discharge
fresh water from Lake Rousseau into the lower river segment. This connection essentially
rechannels the Withlacoochee River below the CFBC and limits releases to the Lower
Withlacoochee River; the maximum daily value was reported by U.S.G.S. to be
approximately 1,840 cubic feet per second (cfs).
The bypass channel branches off the barge canal approximately 3,500 feet downstream of
the canal's connection to Lake Rousseau and extends to the lower segment of the
river (Lower Withlacoochee River) near the point at which the barge canal separates the
upper and lower segments. Although the bypass channel receives most of the flow from
Lake Rousseau now, flow through the channel is regulated by the Inglis bypass spillway, a
gated concrete structure located on the lower end of the channel. The water level in the
bypass channel above this structure is equal to the water level of Lake Rousseau, generally
about 27.5 feet mean sea level (NGVD29). Below the bypass spillway, the water level is a
maximum of 5 feet NGVD29. Essentially, Inglis Dam, the bypass channel spillway, and
Inglis Lock together maintain the level of Lake Rousseau.
In the early 1990's, the barge canal was deauthorized as a federal project. Section 402 of the
Water Resources Development Act of 1990, Public Law 101-640, provided the basis for final
deauthorization of the barge canal project and transfer to the State of Florida of all lands and
interests in lands in and adjacent to the barge canal.
2. Data Source
U. S. Geological Survey (USGS) has two gauging stations near the Inglis Dam.
•
Withlacoochee River at Inglis Dam near Dunnellon, FL (USGS Station ID 02313230)
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HISTORICAL FLOW DATA ANALYSIS AT INGLIS DAM, CITRUS COUNTY, FLORIDA
•
Withlacoochee River below Inglis Dam near Dunnellon, FL (USGS Station ID 02313231)
Historical gage height information is available at both the stations. Flow data is available for
only for one station (USGS station ID 02313230), the period of record available is from 1969
to 2007 (Attachment A). The total drainage area contributing to this station is 2,020 square
miles. Flow records at the station also include the contribution of groundwater
(approximately 70 cfs). The U.S.G.S. reports this flow as mostly leakage from Lake
Rousseau. Flow release at the Inglis Dam is regulated by manipulation of gates in the
spillway.
3. Data Analysis
Statistical analysis was conducted on available daily flow data. The number of releases,
average annual, median and maximum flow rate was estimated from the period of record
(Table 1). Under future conditions, the Levy Nuclear Plant (LNP) cooling water will
withdraw about 190 cfs, so flow down the OWR of less than this value will likely be
withdrawn by LNP. Therefore, the estimate of the number of releases per year was for the
number of days with releases more than 195 cfs to determine how often flows from the dam
may move toward the Gulf. The flow records included the 70 cfs groundwater flow in the
reported values so the reported minimum flow below the dam was always 70 cfs.
For the entire period of record the average annual flow was 436 cfs, median value was 80
cfs, and maximum flow reported as 6,030 cfs. Statistical analysis was also performed on
daily flow data for the days when flow exceeded 195 cfs (the intake flows at the LNP is
estimated to be approximately. Average annual flow for this case was 987 cfs, median value
was 612 cfs, and maximum flow was 6,030 cfs1.
A return period estimation was conducted using the maximum reported flow for each year
(partial series analysis). The statistical analysis tool DISTRIB 2.13 was used for computing
the return period. DISTRIB 2.13 is a statistical distribution analysis tool provided with
Stormwater Management and Design Aid (SMADA) tool (website:
http://www.cee.ucf.edu/software/index.htm). Among the available distribution functions,
a Log Pearson Type III Distribution provided the best-fit. Table 2 provides a return period
estimate based on the measured data and Figure 1 presents the fitted probability
distribution function curve for the return period.
1Note
that this analysis does not include the additional flows transmitted to the Lower Withlacoochee River through the
Bypass Spillway. During the high flows over the Inglis Dam, flow through the Bypass was about 1,200 cfs (see attachment).
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HISTORICAL FLOW DATA ANALYSIS AT INGLIS DAM, CITRUS COUNTY, FLORIDA
TABLE 1.
Statistical Analysis Results of Historical Flow Data at the USGS Gauging Station at Inglis Dam
Year
Number of Releases per Year
in Excess of 195 cfs
Median Value
(cfs)
Average Annual
(cfs)
Maximum Flow
(cfs
1969
92
2,600
2,420
3,300
1970
232
300
1,013
3,600
1971
125
180
282
1,450
1972
128
75
348
2,540
1973
102
70
164
1,110
1974
121
70
414
2,560
1975
3
70
74
320
1976
87
70
144
890
1977
0
70
73
152
1978
105
70
236
2,220
1979
88
70
434
4,500
1980
8
70
94
1,500
1981
0
70
75
133
1982
228
840
1,095
4,280
1983
342
881
948
3,000
1984
286
538
565
2,180
1985
102
70
412
3,560
1986
125
70
229
1,190
1987
164
70
456
3,420
1988
223
290
574
4,190
1989
112
70
164
919
1990
95
70
172
900
1991
96
70
231
1,620
1992
97
70
179
2,320
1993
136
70
155
624
1994
236
460
493
1,910
1995
347
612
859
2,790
1996
246
460
478
2,070
1997
90
70
182
3,480
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HISTORICAL FLOW DATA ANALYSIS AT INGLIS DAM, CITRUS COUNTY, FLORIDA
TABLE 1.
Statistical Analysis Results of Historical Flow Data at the USGS Gauging Station at Inglis Dam
Year
Number of Releases per Year
in Excess of 195 cfs
Median Value
(cfs)
Average Annual
(cfs)
Maximum Flow
(cfs
1998
262
460
1,643
6,000
1999
147
141
176
1,070
2000
70
70
116
948
2001
87
70
162
1,300
2002
101
70
220
1,690
2003
313
1,150
1,270
3,610
2004
143
70
934
6,030
2005
273
617
729
3,080
2006
61
105
171
2,830
2007
5
105
109
776
TABLE 2
Return Period Estimation Using the Statistical Distribution Analysis “DISTRIB 2.13” Model
Return Period
(years)
Predicted Flow
(cfs)
500
5,973
100
5,684
50
5,450
25
5,113
10
4,441
5
3,681
3
2,922
2
2,145
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HISTORICAL FLOW DATA ANALYSIS AT INGLIS DAM, CITRUS COUNTY, FLORIDA
Log Pearson Type III Distribution
7000
6000
Flow (cfs)
5000
4000
3000
2000
1000
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Probability
Actual
Distribution
FIGURE 1
Probability Distribution Function Curve for Maximum Report Flows at Inglis Dam
4. Reference
USGS. USGS 02313230 Withlacoochee River at Inglis Dam near Dunnellon, FL. Website:
http://waterdata.usgs.gov/nwis/dv/?site_no=02313230&referred_module=sw.
Accessed December 18, 2008.
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HISTORICAL FLOW DATA ANALYSIS AT INGLIS DAM, CITRUS COUNTY, FLORIDA
Attachment
USGS 02313250 WITHLACOOCHEE R BYPASS CHANNEL
NR INGLIS FLA
Available data for this site
Time-series: Annual statistics
GO
Output formats
Levy County, Florida
HTML table of all data
Hydrologic Unit Code 03100208
Latitude 29°01'15", Longitude 82°38'17" NAD27 Tab-separated data
Reselect output format
Water Year
338884-TMEM-090, REV 0
00060, Discharge, cubic
feet per second
1971
1,177
1972
1,170
1973
1,061
1974
1,124
1975
984.1
1976
1,115
1977
1,040
1978
1,195
1979
1,146
1980
1,282
1981
836.6
1982
1,099
1983
1,239
1984
1,488
1985
931.6
1986
1,217
1987
1,141
1988
1,106
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HISTORICAL FLOW DATA ANALYSIS AT INGLIS DAM, CITRUS COUNTY, FLORIDA
Water Year
00060, Discharge, cubic
feet per second
1989
1,200
1990
711.8
1991
849.6
1992
643.7
1993
871.8
1994
772.2
1995
975.3
1996
1,264
1997
781.7
1998
1,246
1999
1,091
2000
551.0
2001
453.9
2002
897.8
2003
1,352
2004
1,171
2005
1,347
2006
1,080
2007
639.8
** No Incomplete data have been used for statistical calculation
Highest reported value highlighted in yellow.
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