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
2019
Historical
period of record
High 0.159 0.243
Mean 0.0068 0.0086 0.01897809
Low 0.0005 0.0005
No. of Samples 118 1,032

Five-year Rolling Average

  • Annual Mean
Pass

Nitrogen, Total

Score: Pass
Units: mg/l Year
2019
Historical
period of record
High 2.39 3.108
Mean 1.0268 1.0402 0.42870373
Low 0.069 0.069
No. of Samples 116 664

Five-year Rolling Average

  • Annual Mean
Pass

Phosphorus, Total

Score: Pass
Units: mg/l Year
2019
Historical
period of record
High 0.291 1.19
Mean 0.0936 0.1482 0.1523878
Low 0.008 0.008
No. of Samples 116 1,085

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
2019
Historical
period of record
High 140.261 227.16
Mean 52.0 65.47 31.53792
Low 6.10 1.80
No. of Samples 59 1,188

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2019
Historical
period of record
High 4.75 13.90
Mean 1.4 1.55 1.43205
Low 1.00 0.00
No. of Samples 114 1,015

Five-year Rolling Average

  • Annual Mean

Color

Units: PCU Year
2019
Historical
period of record
High 260.00 650.00
Mean 106.51 94.89 89.91147
Low 30.00 5.00
No. of Samples 116 1,398

Five-year Rolling Average

  • Annual Mean

Escherichia coli

Units: cfu/100ml Year
2019
Historical
period of record
High 1467.00 1467.00
Mean 28.42 26.56 143.81724
Low 10.00 10.00
No. of Samples 92 265

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2019
Historical
period of record
High 566.00 605.00
Mean 22.03 17.14 88.00411
Low 8.00 0.00
No. of Samples 116 1,211

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2019
Historical
period of record
High 2320.00 8400.00
Mean 981.33 1023.42 455.68243
Low 65.00 0.00
No. of Samples 116 1,161

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2019
Historical
period of record
High 172.00 2210.00
Mean 28.31 23.04 89.88663
Low 4.00 0.00
No. of Samples 116 1,081

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2019
Historical
period of record
High 8.97 22.31
Mean 7.17 7.57 0.44842
Low 6.34 5.80
No. of Samples 59 4,385

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2019
Historical
period of record
High 33.4845 76.50
Mean 0.35 16.8 16.765
Low 0.0642 0.00
No. of Samples 57 3,957

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2019
Historical
period of record
High 50133.10 59844.40
Mean 682.71 14192.03 19557.31963
Low 135.91 0.10
No. of Samples 61 4,338

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2019
Historical
period of record
High 91.1795 211.586
Mean 77.78 77.6 9.68
Low 61.34 47.372
No. of Samples 59 4,070

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2019
Historical
period of record
High 2.60 48.00
Mean 2.55 2.97 3.21886
Low 2.50 0.40
No. of Samples 2 969

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 »

Chart Legend
  • Trend Line
  • Annual Mean
  • Threshold
Water quality data are not available for the tidal portion of this creek.

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 2017 143 16 159 10

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