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

4 out of 4 indicators were rated as PASS.

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

Learn more about how this report is created

  • 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

Cow Pen Slough

Water Chemistry Ratings | Freshwater Portion of the Creek

Creek Conditions Ratings are based on comparing nitrogen, phosphorus, chlorophyll and dissolved oxygen to water quality guidelines or regulations. Florida law defines a maximum allowable concentration of nitrogen, phosphorus, and chlorophyll a, and a minimum allowable concentration of dissolved oxygen in these streams. Learn more about these ratings and how they are calculated »

Data for the following WBIDs is averaged when compiling the data below:
  • 1924
  • 1924B
  • 1987
  • 1994
  • 1996
  • 2004
Chart Legend
  • Trend Line
  • Annual Mean
  • Threshold
Pass

Chlorophyll a

Score: Pass
Units: mg/l Year
2023
Historical
period of record
High 0.0307 0.312
Mean 0.0087 0.0079 0.02285859
Low 0.0015 0.0003
No. of Samples 26 672

Five-year Rolling Average

  • Annual Mean
Pass

Nitrogen, Total

Score: Pass
Units: mg/l Year
2023
Historical
period of record
High 3.695 3.695
Mean 1.2531 1.1559 0.41796282
Low 0.77 0.069
No. of Samples 26 626

Five-year Rolling Average

  • Annual Mean
Pass

Phosphorus, Total

Score: Pass
Units: mg/l Year
2023
Historical
period of record
High 0.542 1.19
Mean 0.1471 0.1301 0.16327189
Low 0.03 0.003
No. of Samples 26 634

Five-year Rolling Average

  • Annual Mean
Pass

Dissolved Oxygen Saturation

Note: Low DO saturation also may be naturally influenced by inflows from nearby wetlands or groundwater sources.
Score: Pass
Units: percent (%) Year
2023
Historical
period of record
High 150.298 227.16
Mean 54.29 59.04 34.74309
Low 7.10 0.00
No. of Samples 40 785

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2023
Historical
period of record
High 7.52 11.80
Mean 1.79 1.48 1.44699
Low 1.00 0.00
No. of Samples 26 587

Five-year Rolling Average

  • Annual Mean

Color

Units: PCU Year
2023
Historical
period of record
High 240.00 500.00
Mean 123.53 110.25 89.86958
Low 40.00 10.00
No. of Samples 36 880

Five-year Rolling Average

  • Annual Mean

Escherichia coli

Units: cfu/100ml Year
2023
Historical
period of record
High 183.00 1467.00
Mean 23.53 24.5 104.17615
Low 10.00 10.00
No. of Samples 26 371

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2023
Historical
period of record
High 330.00 577.00
Mean 12.11 9.87 70.25858
Low 8.00 0.00
No. of Samples 26 745

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2023
Historical
period of record
High 3680.00 8400.00
Mean 1234.28 1126.91 496.03719
Low 746.00 0.00
No. of Samples 26 713

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2023
Historical
period of record
High 62.00 2210.00
Mean 16.19 22.34 112.44589
Low 6.00 0.00
No. of Samples 26 643

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2023
Historical
period of record
High 9.57 11.50
Mean 7.64 7.58 0.38167
Low 6.62 5.80
No. of Samples 40 4,063

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2023
Historical
period of record
High 0.5197 76.50
Mean 0.22 15.56 17.21186
Low 0.0896 0.00
No. of Samples 40 3,786

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2023
Historical
period of record
High 1038.95 59844.40
Mean 453.19 14696.8 19404.71508
Low 188.404 0.0578
No. of Samples 40 4,025

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2023
Historical
period of record
High 200.3354 348.7984
Mean 173.26 80.5 21.8485
Low 153.8492 47.372
No. of Samples 40 3,894

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2023
Historical
period of record
High 23.00
Mean 2.58 2.4718
Low 0.40
No. of Samples 0 445

Five-year Rolling Average

  • Annual Mean
Other Measures of Creek Health:

Water Chemistry Ratings | Tidal Portion of the Creek

Creek Conditions Ratings are based on comparing nitrogen, phosphorus, chlorophyll and dissolved oxygen to water quality guidelines or regulations. Florida law defines a maximum allowable concentration of chlorophyll a and a minimum allowable concentration of dissolved oxygen in these streams. Florida has no regulatory thresholds for nitrogen or phosphorus in tidal creeks so trends are used to rate the creeks. Learn more about these ratings and how they are calculated »

Data for the following WBIDs is averaged when compiling the data below:
  • 1924A
Chart Legend
  • Trend Line
  • Annual Mean
  • Threshold

Chlorophyll a

Units: mg/l Year
2023
Historical
period of record
High 0.0
Mean 0.0104 0.00359453
Low 0.004
No. of Samples 0 15

Five-year Rolling Average

  • Annual Mean

Nitrogen, Total

Units: mg/l Year
2023
Historical
period of record
High 2.2
Mean 1.0974 0.44877328
Low 0.16
No. of Samples 0 41

Five-year Rolling Average

  • Annual Mean

Phosphorus, Total

Units: mg/l Year
2023
Historical
period of record
High 0.6
Mean 0.1906 0.11184856
Low 0.043
No. of Samples 0 38

Five-year Rolling Average

  • Annual Mean

Dissolved Oxygen Saturation

Units: percent (%) Year
2023
Historical
period of record
High 122.5
Mean 73.73 14.44485
Low 48.1012
No. of Samples 0 124

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2023
Historical
period of record
High 1.2
Mean 1.2
Low 1.20
No. of Samples 0 1

Five-year Rolling Average

  • Annual Mean

Color

Units: PCU Year
2023
Historical
period of record
High 300.0
Mean 73.34 69.1682
Low 10.00
No. of Samples 0 108

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2023
Historical
period of record
High 203.0
Mean 1.03 27.60433
Low 0.00
No. of Samples 0 85

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2023
Historical
period of record
High 2,163.0
Mean 1031.76 435.84733
Low 50.00
No. of Samples 0 74

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2023
Historical
period of record
High 250.0
Mean 46.62 66.9655
Low 0.00
No. of Samples 0 44

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2023
Historical
period of record
High 8.6
Mean 7.61 0.33271
Low 6.80
No. of Samples 0 155

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2023
Historical
period of record
High 33.5
Mean 11.19 8.6935
Low 0.00
No. of Samples 0 73

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2023
Historical
period of record
High 55,200.0 57,700.0
Mean 45866.26 16776.56 17437.80179
Low 25400.00 19.00
No. of Samples 324 2,975

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2023
Historical
period of record
High 97.0 105.4
Mean 80.52 79.14 7.70931
Low 63.50 51.80
No. of Samples 325 2,886

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2023
Historical
period of record
High 11.0
Mean 2.8 1.7604
Low 1.00
No. of Samples 0 105

Five-year Rolling 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 2023 90

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 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% 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% 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% 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% 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% 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% Land Use Trend Sparkline
Barren Land 160% 50% 20% 490.1% 1100.2% 770.2% 820.2% 180% 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% Land Use Trend Sparkline
Land Use Chart