Status and Trends of Water
Quality and Benthic Habitats in
the Little Manatee River
Environmental Resources Management (ERM) Division
Environmental Protection Commission of Hillsborough County
3629 Queen Palm Dr.
Tampa, FL 33619-1309
EPCHC Data Sources Available

Water Quality Data



Monthly monitoring at fixed stations (long-term surveillance
network) since the early-1970’s. Includes large number of
chemical and physical parameters
Hillsborough Independent Monitoring Program (HIMP),
monitoring since 1999. Focused on physical parameters
(salinity, DO, pH, temperature). Combination of fixed
stations and 72- hour sensor deployments at randomlyselected locations
Benthic Data


Bay-wide benthic and sediment monitoring since mid-1990’s,
during fall “index period”
HIMP monitoring (focused on tidal reaches of Hillsborough,
Palm Alafia, and Little Manatee rivers) since 1999
Available at:
http://www.epchc.org/himp.htm
EPCHC long-term surface water monitoring network
TIDAL
FRESHWATER
HIMP
Monitoring
Locations
(Tidal)
Benthic Monitoring
Stations
HIMP Water Quality
Monitoring Stations
Other Information Sources

SWFWMD land use mapping program (detailed
land use maps, updated on 5-year cycle)

U.S. Geological Survey stream gaging program
(long-term trends in river flow)

U.S. EPA and FDEP TMDL programs (identify
and restore water quality in “impaired” water
bodies not currently meeting federal/state water
quality standards)
Land Use (1999)
% of Watershed
Altered
47.4 % Agriculture
7.2 % Urbanized
5.7 % Mining
3
Average Annual Discharge (ft /sec)
Sub-Basin Average Annual Rainfall (Inches)
Rainfall / River Flow Trends
Little Manatee River
80
Rainfall - No Trend
70
60
50
40
Year
30
1920
1930
1940
1950
1960
1970
1980
1990
2000
1950
1960
1970
1980
1990
2000
Discharge - No Trend
400
300
200
100
Year
0
1920
1930
1940
20-Year Water Quality Trends
& Recent Conditions
Physical Parameters
Period
Mid-Depth DO
1984 - 2004
No Trend
Mid-Depth
Salinity
No Trend
2004 Average
5.8 ± 0.4
9.6 ± 0.1
0.37 ± 0.15
1984 - 2004
Decreasing
No Trend
.
2004 Average
7.1 ± 0.3
0.16 ± 0.05
.
Stratification
Decreasing
Tidal
Freshwater
Nutrient & Bacterial Parameters
Total
Total Nitrogen
Phosphorus
Decreasing
No Trend
Fecal
Coliforms
No Trend
Period
Chlorophyll-a
1984 - 2004
No Trend
2004 Average
5.75 ± 1.1
0.34 ± 0.04
0.88 ± 0.12
347 ± 269
1984 - 2004
Decreasing
No Trend
No Trend
Decreasing
2004 Average
1.05 ± 0.3
0.61 ± 0.04
1.51 ± 0.09
1188 ± 419
Tidal
Freshwater
Water Quality Comparisons
Tidal River Stations
(based on 1984 – 2003 EPCHC monitoring data)
Location
Dissolved Salinity
Oxygen
(ppt)
(mg/L)
Total
Phosphorus
(mg P/L)
Total
Chlorophyll
-a
Nitrogen
(µg/L)
(mg N/L)
Fecal
Coliforms
(col/100 ml)
Little
Manatee
River
5.0
12.2
0.4
1.1
7.3
132
Alafia
River
4.6
18.1
1.0
1.4
20.5
228
Hillsborough
River
4.6
13.4
0.3
1.1
14.7
409
Palm
River
4.3
23.5
0.4
1.2
21.4
189
Mean Dissolved Oxygen Conc. (mg/L) ± 95% C.I.
Recent Bottom Dissolved Oxygen
Conditions (HIMP Data) - Diurnal
HIMP Continuous Monitoring Data (2000 - 2005)
8
72-Hr Depl. at Mul. Stations (N~200+ per Point)
Single Fixed Station (N~790 per Point)
7
6
5
4
Instantaneous State Standard
3
2
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time of Day
14
15
16
17
18
19
20
21
22
23
0
Date
4/05
4
2/05
12/04
10/04
8/04
6/04
4/04
2/04
12/03
10/03
8/03
6/03
4/03
2/03
12/02
10/02
8/02
6/02
4/02
2/02
12/01
10/01
8/01
6/01
4/01
2/01
10
20
10
8
2
0
Rainfall
12/00
Mean Daily DO Conc. (mg/L) ± 95% C.I.
Recent Bottom Dissolved Oxygen
Conditions (HIMP Data) - Daily
HIMP Continuous Monitoring Data (2000 - 2005)
0
6
24- Hr Mean
State Standard
0.5
CUMULATIVE PROPORTION
0.6
1.0
CUMULATIVE PROPORTION
Relative Frequency of Bottom
Dissolved Oxygen < 2.0 mg/L
Dissolved Oxygen Conditions
Relative to Other Tidal Rivers
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.4
0.8
0.6
0.4
RIVER
0.2
0.0
0
HR
LMR
1
2
3 4
5
6
7
8
9
DISSOLVED OXYGEN [PPM]
10
0.3
0.2
0.1
0.0
Lit. Man. R.
Alafia R.
Hills. R.
Study Sites
Palm R.
RIVER
AR
LMR
0
1 2 3 4 5 6 7 8
DISSOLVED OXYGEN [PPM]
9
10
Impaired Waters, LMR and vicinity
Lower LMR & South Fork of LMR
Impaired for DO, Coliforms, & Nutrients
TMDLs due in 2008
Tampa Bay Watershed
Impaired Waters
Little Manatee River Benthic Habitats
More coarse-grained (sand) sediments and less silt/clay
than the other tidal rivers
% COMPOSITION
40
AR
LMR
30
20
10
0
TF
CUMULATIVE PROPORTION

1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-M W-S LI-M LI-S O-M O-S Y-M Y-S
O ES ES O L O L
O
TF
P
P
M
M
W
AREA
LMR
MCB
PR
0
10 20 30 40 50 60 70 80 90 100
SILT + CLAY [%]
CUMULATIVE PROPORTION
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
RIVER
HR
LMR
10
20 30 40 50 60
NUMBERS OF TAXA [S]
CUMULATIVE PROPORTION
CUMULATIVE PROPORTION
Comparison of Benthic Species Diversity
and Abundance to Other Tidal Rivers
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
70
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
LMR
MCB
PR
10
20
30
40
50
NUMBERS TAXA
AR
LMR
1
10
0
10
00
10
0
00
10
N+1 NUMBERS M
-2
00
00
0
1
60
70
Summary – LMR Water Quantity and Quality

No trends in rainfall or annual river flow, but dry-season
flow in the LMR has shown an increasing trend since 1940
(SWFWMD studies suggest agricultural irrigation as the
cause)

Over the past 20 years, nutrient and chlorophyll levels have
improved (declined) at EPC monitoring stations on the LMR

Two LMR segments currently considered “impaired” (for
coliform bacteria, nutrients and DO). TMDLs due in 2008

Relative to the other tidal rivers in Hillsborough County, the
LMR appears to have the best water quality
Summary – Benthic habitats and organisms

Sandy sediments are the predominant habitats in the tidal
portion of the LMR. Higher silt+clay levels are present in
the other rivers

Relative to the other tidal rivers in Hillsborough County,
benthic species richness and abundance are generally
higher in the LMR
Future Directions – Watershed Management
• EPC is working with several partners (Hillsborough County, City of Tampa,
SWFWMD, TBEP, FDEP) to develop a county-wide, multi-stakeholder
watershed management program
• A primary purpose would be to restore and protect the County’s surface
(and ground) water resources, to support future environmental and
economic needs
• Would help the County comply with Federal and State water quality
protection and restoration (MS4 and TMDL) requirements
• Will require significant co-ordination among programs in several agencies
and departments
• Planning, zoning and growth management issues are critical elements of
the watershed management process