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

The hydrologic boundary of the Cow Pen Slough Basin is indeterminate in many areas due to the flat topography and undefined drainageways. Drainage from the basin is conveyed through 14 miles of improved channel. There are two operational flood control structures on the channel which were designed to provide grade control and water conservation. At present the Cow Pen Slough Basin is primarily rural in nature, with the majority of the land uses being classified as rangeland, crop and pastureland, orchards and groves, and upland forests. There are localized areas that are primarily urban in nature around Bee Ridge and north of Venice, with the majority being classified as residential. For basin details see: Cow Pen Slough Basin Master Plan (USDA Report, 1997)

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
2020
Historical
period of record
High 0.0656 0.243
Mean 0.0075 0.0085 0.0185912
Low 0.0011 0.0005
No. of Samples 56 860

Five-year Rolling Average

  • Annual Mean
Pass

Nitrogen, Total

Score: Pass
Units: mg/l Year
2020
Historical
period of record
High 2.064 3.108
Mean 1.0975 1.0459 0.42251128
Low 0.528 0.069
No. of Samples 55 804

Five-year Rolling Average

  • Annual Mean
Pass

Phosphorus, Total

Score: Pass
Units: mg/l Year
2020
Historical
period of record
High 0.551 1.19
Mean 0.1684 0.1502 0.15406895
Low 0.018 0.008
No. of Samples 55 903

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
2020
Historical
period of record
High 142.513 227.16
Mean 53.22 63.24 32.26514
Low 10.5214 1.80
No. of Samples 55 1,009

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2020
Historical
period of record
High 7.49 13.90
Mean 1.45 1.55 1.44223
Low 1.00 0.00
No. of Samples 54 857

Five-year Rolling Average

  • Annual Mean

Color

Units: PCU Year
2020
Historical
period of record
High 420.00 650.00
Mean 145.68 95.01 92.57283
Low 50.00 5.00
No. of Samples 55 1,093

Five-year Rolling Average

  • Annual Mean

Escherichia coli

Units: cfu/100ml Year
2020
Historical
period of record
High 295.00 1467.00
Mean 26.76 26.31 115.3834
Low 10.00 10.00
No. of Samples 43 263

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2020
Historical
period of record
High 394.00 605.00
Mean 25.33 15.1 88.1149
Low 8.00 0.00
No. of Samples 55 1,027

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2020
Historical
period of record
High 2060.00 8400.00
Mean 1029.71 1025.98 474.0786
Low 418.00 0.00
No. of Samples 55 987

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2020
Historical
period of record
High 227.00 2210.00
Mean 29.22 22.84 96.24951
Low 4.00 0.00
No. of Samples 55 910

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2020
Historical
period of record
High 7.95 11.50
Mean 7.18 7.56 0.39213
Low 6.45 5.70
No. of Samples 55 4,342

Five-year Rolling Average

  • Annual Mean

Rainfall

Units: inches Year
2020
Historical
period of record
High 56.99 70.27
Mean 21.0280229594542
Low 3.15
No. of Samples 366 4,725

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2020
Historical
period of record
High 29.7078 76.50
Mean 0.42 15.32 17.07179
Low 0.0637 0.00
No. of Samples 54 4,035

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2020
Historical
period of record
High 45167.90 59844.40
Mean 814.79 14229.46 19525.54577
Low 135.266 0.10
No. of Samples 56 4,282

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2020
Historical
period of record
High 55.40 92.426
Mean 55.4 77.45 7.64853
Low 55.40 47.372
No. of Samples 1 4,066

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2020
Historical
period of record
High 3.20 48.00
Mean 3.2 2.93 3.42746
Low 3.20 0.40
No. of Samples 1 798

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
2020
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
2020
Historical
period of record
High 2.2
Mean 1.0972 0.44363338
Low 0.16
No. of Samples 0 42

Five-year Rolling Average

  • Annual Mean

Phosphorus, Total

Units: mg/l Year
2020
Historical
period of record
High 0.6
Mean 0.1913 0.11036761
Low 0.043
No. of Samples 0 39

Five-year Rolling Average

  • Annual Mean

Dissolved Oxygen Saturation

Units: percent (%) Year
2020
Historical
period of record
High 122.5
Mean 73.4 14.47615
Low 48.1012
No. of Samples 0 128

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2020
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
2020
Historical
period of record
High 300.0
Mean 72.04 68.50301
Low 10.00
No. of Samples 0 112

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2020
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
2020
Historical
period of record
High 2,163.0
Mean 1032.51 432.97307
Low 50.00
No. of Samples 0 75

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2020
Historical
period of record
High 250.0
Mean 46.62 66.63103
Low 0.00
No. of Samples 0 45

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2020
Historical
period of record
High 8.6
Mean 7.61 0.3315
Low 6.80
No. of Samples 0 160

Five-year Rolling Average

  • Annual Mean

Rainfall

Units: inches Year
2020
Historical
period of record
High 57.0 70.3
Mean 21.0280229594542
Low 3.15
No. of Samples 366 4,725

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2020
Historical
period of record
High 33.5
Mean 11.59 8.63974
Low 0.00
No. of Samples 0 77

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2020
Historical
period of record
High 47,300.0 51,500.0
Mean 17559.13 12312.55 17380.44759
Low 236.00 19.00
No. of Samples 366 1,988

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2020
Historical
period of record
High 92.8 93.2
Mean 79.64 78.92 7.49512
Low 61.70 51.80
No. of Samples 366 1,899

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2020
Historical
period of record
High 11.0
Mean 2.82 1.74921
Low 1.00
No. of Samples 0 109

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 2020 41 26 67 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 2011 2014 Trend
Urban & Built-up 4,5089.5% 11,73024.7% 11,97425.2% Land Use Trend Sparkline
Agriculture 13,32028% 13,51228.4% 13,22727.8% Land Use Trend Sparkline
Rangeland 7,04114.8% 2,3074.9% 2,4885.2% Land Use Trend Sparkline
Upland Forests 11,44524.1% 7,37615.5% 7,30915.4% Land Use Trend Sparkline
Water 8161.7% 1,7633.7% 1,8173.8% Land Use Trend Sparkline
Wetlands 10,03521.1% 9,50720% 9,39719.8% Land Use Trend Sparkline
Barren Land 160% 1100.2% 770.2% Land Use Trend Sparkline
Transportation and Utilities 3370.7% 1,2132.6% 1,2302.6% Land Use Trend Sparkline
Land Use Chart