Pass
Rating icon - Chlorophyll a Rating icon - Total Nitrogen Rating icon - Total Phosphorous Rating icon - Dissolved Oxygen Saturation

4 out of 4 primary indicators were rated as PASS.

"Primary" are nutrient related (Chl, N, P) and bacteria (B) parameters.

All four indicators must pass for the creek to be rated as PASS.

Greyed out values indicate no data for the report year.

  • Size: 47,518 acres
  • Location: North and central Sarasota County, south Manatee County
  • Discharges into: Dona Bay

For more information, please see: Cow Pen Slough Basin Master Plan (USDA Report, 1997)

View county-wide water quality trends »

Cow Pen Slough

Water Chemistry Ratings

Monitoring data is analyzed to determine stream health based on State water quality standards. Official determination of impairment or attainment of the water quality standards is performed by FDEP and is based on at least three years and up to seven and a half years of data. Information on approximately 17 different parameters are collected at stream sites, but only total nitrogen, total phosphorus, chlorophyll a, dissolved oxygen (percent saturation), and bacteria are assessed according to established water quality criteria mandated by the Clean Water Act. Additionally, the floral and faunal communities (SCI) are assessed at some sites to determine whether waters support a healthy aquatic community.

The "pass/fail" conditions presented here do not indicate impairment as determined by the official Florida Department of Environmental Protection Impaired Waters Rule assessment but, rather, give an indication of stream condition in a particular year in relation to the set regulatory numeric limits. Streams receive an annual "PASS" rating for each parameter if the mean value is below the regulatory value and a "FAIL" rating if the mean value exceeds the regulatory value. Not all water quality parameters have an established numeric criterion, so only some of the graphs below show the regulatory limit, represented by a horizontal red line.

Chart Legend
  • Monthly Average
  • Threshold
  • Annual Mean

The graphs here illustrate results over the past five years. Data from sites monitored within a single waterbody identification basin (WBID) are combined to determine water quality status for each WBID, and the annual geometric mean of sample results is indicated on the graph for the most recent year. The table to the left of the graph gives the annual and historic range of values for the indicator.

Click the graph to view a larger image and to download the full dataset.

Freshwater Portion of the Creek

Data for the following WBIDs is averaged when compiling the data below:
  • 1924
  • 1924B
  • 1987
  • 1994
  • 1994A
  • 1996
  • 2004

Chlorophyll a

Units: µg/l Year
2013
Historical
period of record
High 61.70 243.00
Mean 9.1976 10.8714 21.44097
Low 1.38 0.62
No. of Samples 74 533
  • Monthly Average
  • NNC 20.00 µg/l
  • Annual Mean

Nitrogen, Total

Units: mg/L Year
2013
Historical
period of record
High 1.791 2.73
Mean 1.034 0.9744 0.44258065
Low 0.508 0.15
No. of Samples 24 343
  • Monthly Average
  • NNC 1.65 mg/L
  • Annual Mean

Phosphorus, Total

Units: mg/L Year
2013
Historical
period of record
High 0.356 1.19
Mean 0.1559 0.1782 0.16935593
Low 0.057 0.02
No. of Samples 72 583
  • Monthly Average
  • NNC 0.49 mg/L
  • Annual Mean

Dissolved Oxygen Saturation

Note: Dissolved oxygen saturation percentages above the regulatory threshold meet established water quality targets.
Units: percent (%) Year
2013
Historical
period of record
High 144.70 227.16
Mean 67.52 72.15 31.84271
Low 17.40 2.381
No. of Samples 68 805
  • Monthly Average
  • NNC 38.00 percent (%)
  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2013
Historical
period of record
High 4.52 13.90
Mean 1.71 1.74 1.66367
Low 0.50 0.00
No. of Samples 72 541
  • Monthly Average
  • Annual Mean

Color

Units: PCU Year
2013
Historical
period of record
High 650.00
Mean 85.82 87.0036
Low 10.00
No. of Samples 0 274
  • Monthly Average
  • Annual Mean

Escherichia coli

Units: MPN/100ml Year
2013
Historical
period of record
High 230.00
Mean 117.47 120.20815
Low 60.00
No. of Samples 0 2
  • Monthly Average
  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: mg/L Year
2013
Historical
period of record
High 0.142 0.605
Mean 0.02 0.02 0.09756985
Low 0.008 0.00
No. of Samples 72 680
  • Monthly Average
  • Annual Mean

Nitrogen, Kjeldahl

Units: mg/L Year
2013
Historical
period of record
High 1.63 8.40
Mean 1.0 0.99 0.49142583
Low 0.502 0.00
No. of Samples 72 667
  • Monthly Average
  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: mg/L Year
2013
Historical
period of record
High 0.181 2.21
Mean 0.02 0.02 0.10024273
Low 0.004 0.00
No. of Samples 71 591
  • Monthly Average
  • Annual Mean

pH

Units: None Year
2013
Historical
period of record
High 8.17 11.50
Mean 7.49 7.59 0.36995
Low 6.87 5.80
No. of Samples 68 3,890
  • Monthly Average
  • Annual Mean

Salinity

Units: PSS Year
2013
Historical
period of record
High 31.02 76.50
Mean 1.12 22.95 15.40504
Low 0.12 0.00
No. of Samples 66 3,588
  • Monthly Average
  • Annual Mean

Specific conductance

Units: µmho Year
2013
Historical
period of record
High 47567.00 59844.40
Mean 2056.37 18387.05 18275.99441
Low 253.00 0.512
No. of Samples 68 3,945
  • Monthly Average
  • Annual Mean

Temperature, water

Units: °F Year
2013
Historical
period of record
High 86.846 92.426
Mean 78.3 77.49 7.62561
Low 65.75 47.372
No. of Samples 46 3,712
  • Monthly Average
  • Annual Mean

Turbidity

Units: NTU Year
2013
Historical
period of record
High 6.70 48.00
Mean 3.15 2.88 3.54741
Low 0.45 0.40
No. of Samples 71 734
  • Monthly Average
  • Annual Mean
Other Measures of Creek Health:

Tidal Portion of the Creek

Data for the following WBIDs is averaged when compiling the data below:
  • 1924A
  • 1994B

Chlorophyll a

Units: µg/l Year
2013
Historical
period of record
High 16.7
Mean 10.4029 3.59453
Low 4.01
No. of Samples 0 15
  • Monthly Average
  • NNC 11.00 ug/l
  • Annual Mean

Nitrogen, Total

Units: mg/L Year
2013
Historical
period of record
High 2.2
Mean 1.0972 0.44363338
Low 0.16
No. of Samples 0 42
  • Monthly Average
  • Annual Mean

Phosphorus, Total

Units: mg/L Year
2013
Historical
period of record
High 0.6
Mean 0.1913 0.11036761
Low 0.043
No. of Samples 0 39
  • Monthly Average
  • Annual Mean

Dissolved Oxygen Saturation

Note: Dissolved oxygen saturation percentages above the regulatory threshold meet established water quality targets.
Units: percent (%) Year
2013
Historical
period of record
High 122.5
Mean 73.4 14.47615
Low 48.1012
No. of Samples 0 128
  • Monthly Average
  • NNC 56.00 percent (%)
  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2013
Historical
period of record
High 1.2
Mean 1.2
Low 1.20
No. of Samples 0 1
  • Monthly Average
  • Annual Mean

Color

Units: PCU Year
2013
Historical
period of record
High 300.0
Mean 72.04 68.50301
Low 10.00
No. of Samples 0 112
  • Monthly Average
  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: mg/L Year
2013
Historical
period of record
High 0.2
Mean 0.0 0.02760433
Low 0.00
No. of Samples 0 85
  • Monthly Average
  • Annual Mean

Nitrogen, Kjeldahl

Units: mg/L Year
2013
Historical
period of record
High 2.2
Mean 1.03 0.43297307
Low 0.05
No. of Samples 0 75
  • Monthly Average
  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: mg/L Year
2013
Historical
period of record
High 0.3
Mean 0.05 0.06663103
Low 0.00
No. of Samples 0 45
  • Monthly Average
  • Annual Mean

pH

Units: None Year
2013
Historical
period of record
High 8.6
Mean 7.61 0.3315
Low 6.80
No. of Samples 0 160
  • Monthly Average
  • Annual Mean

Salinity

Units: PSS Year
2013
Historical
period of record
High 33.5
Mean 11.59 8.63974
Low 0.00
No. of Samples 0 77
  • Monthly Average
  • Annual Mean

Specific conductance

Units: µmho Year
2013
Historical
period of record
High 51,300.0
Mean 14280.55 15826.70882
Low 19.00
No. of Samples 0 335
  • Monthly Average
  • Annual Mean

Temperature, water

Units: °F Year
2013
Historical
period of record
High 93.2
Mean 75.64 9.15805
Low 51.80
No. of Samples 0 248
  • Monthly Average
  • Annual Mean

Turbidity

Units: NTU Year
2013
Historical
period of record
High 11.0
Mean 2.82 1.74921
Low 1.00
No. of Samples 0 109
  • Monthly Average
  • Annual Mean
Other Measures of Creek Health:

Oysters

Because they are immobile and will tolerate a fairly wide salinity range, eastern oysters (Crassostrea virginica) are valuable as an indicator of the relative health of aquatic ecosystems in the tidally-influenced portions of coastal creeks. Sarasota County has established an oyster monitoring program to track the location, types, and status of oyster reefs. Data from this monitoring program is shown below. Learn more about Oysters »

Loading oyster site map...
Most Recent Sarasota County Oyster Monitoring Program Data
Icon Site ID Year Dead Live Total % Live
1 SKC4 2013 312 190 502 38

Impervious Features

Cow Pen Slough is located within the Sarasota Bay Watershed. View details about the Sarasota Bay Watershed »

Rain that falls on land that is in a natural state is absorbed and filtered by soils and vegetation as it makes it way into underground aquifers. However, in developed areas, "impervious surfaces" impede this process and contribute to polluted urban runoff entering surface waters. These surfaces include human infrastructure like roads, sidewalks, driveways and parking lots that are covered by impenetrable materials such as asphalt, concrete, brick and stone, as well as buildings and other permanent structures. Soils that have been disturbed and compacted by urban development are often impervious as well. Learn more about Impervious Features »

The Sarasota County Stormwater Environmental Utility (SEU) mapped impervious surfaces in the County in 2013. A map showing impervious surfaces can be viewed using the Water Atlas Map Viewer tool.

2% of the land area within the Cow Pen Slough Basin is covered by impervious surfaces

Impervious Surface Coverage by Type

Land Use / Land Cover

Cow Pen Slough is located within the Sarasota Bay Watershed. View details about the Sarasota Bay Watershed »

Land use within a creek's watershed has a major effect on its water quality. In general, less development means better water quality. Land Cover/Land Use classifications categorize land in terms of its observed physical surface characteristics (e.g. upland or wetland), and also reflect the types of activity that are taking place on it (agriculture, urban/built-up, utilities, etc.). Florida uses as its standard a set of statewide classifications which were developed by the Florida Department of Transportation. Learn more about Land Use and Land Cover »

Acreage and Percentage within each Land Use / Land Cover Category for Cow Pen Slough Basin
Land Use Classification 1990 1995 1999 2005 2011 2014 2017 2020 2023 Trend
Urban & Built-up 4,5089.5% 6,03812.7% 8,97518.9% 11,00123.2% 11,73024.7% 11,97425.2% 12,40026.1% 13,13127.6% 14,08629.6% Land Use Trend Sparkline
Agriculture 13,32028% 14,16429.8% 14,11229.7% 14,34730.2% 13,51228.4% 13,22727.8% 13,18427.7% 12,67726.7% 11,85324.9% Land Use Trend Sparkline
Rangeland 7,04114.8% 6,16813% 4,0568.5% 2,4485.2% 2,3074.9% 2,4885.2% 2,0504.3% 1,7573.7% 1,6823.5% Land Use Trend Sparkline
Upland Forests 11,44524.1% 10,05921.2% 8,50317.9% 7,48315.7% 7,37615.5% 7,30915.4% 7,13115% 6,79114.3% 6,58813.9% Land Use Trend Sparkline
Water 8161.7% 1,3452.8% 1,5213.2% 1,6443.5% 1,7633.7% 1,8173.8% 1,9414.1% 1,9764.2% 2,1984.6% Land Use Trend Sparkline
Wetlands 10,03521.1% 9,31019.6% 9,36719.7% 9,47119.9% 9,50720% 9,39719.8% 9,44119.9% 9,82620.7% 9,71620.4% Land Use Trend Sparkline
Barren Land 160% 50% 20% 490.1% 1100.2% 770.2% 820.2% 180% 450.1% Land Use Trend Sparkline
Transportation and Utilities 3370.7% 4300.9% 9822.1% 1,0752.3% 1,2132.6% 1,2302.6% 1,2882.7% 1,3422.8% 1,3552.9% Land Use Trend Sparkline
Land Use Chart