# Nassau

- St. Marys Basin
Lakes, Rivers, Streams, and Aquifers

Florida Department of

Environmental Protection

**Division of Environmental Assessment**

**and Restoration**

Bureau of Assessment and Restoration Support, Watershed Monitoring Section



### Good science is the foundation of the Florida Department of Environmental Protection’s (FDEP) programs to assess and protect water quality. FDEP is committed to characterizing the environmental conditions of Florida’s freshwater resources through several monitoring programs. The Watershed Monitoring Section administers the Status Monitoring Network

, which oversees the statewide sampling of surface and ground water. This report summarizes the 200 7 Status Monitoring Network results for the Nassau

- St. Marys Basin

.



## Nassau

- St. Marys Basin

The Nassau

- St. Marys Basin occupies approximately 1436 square miles in northeastern Florida, with part of the St. Marys Basin (643 square miles) located in southeastern Georgia. A ll or part of 5 counties in Florida (Baker, Columbia, Duval, Nassau, and Union) and 3 counties in Georgia (Camden, Charlton, and Ware ) are part of the Nassau

- St. Marys Basin

. The Nassau River forms the boundary between Nassau and Duval Counties just north of Jacksonville. The St. Marys River forms the border between southeast Georgia and northeast Florida. The St. Marys River, a blackwater stream that originates in the Okefenokee Swamp, extends 125 to 130 miles before discharging to Cumberland Sound and the Atlantic Ocean.

The prominent land use and land covers in the Nassau

- St. Marys Basin are silviculture, wetlands and forest, primarily managed pine forests. The population in the Nassau

- St. Marys Basin is relatively low, with the highest population densities found in Fernandina Beach, Yulee, and Macclenny. Amelia Island is a popular tourist destination. Major industries in the area are farming (livestock and poultry), silviculture, and commodity production. The Nassau River and estuary support a healthy recreational and commercial fishing industry, especially commercial c rabbing and shrimping.

Natural areas cover a substantial portion of the Nassau

- St. Marys Basin. Some of the larger conservation and recreation lands include the Amelia Island State Park, Big Talbot Island State Park, Little Talbot Island State Park, Fort Clinch State Park and Aquatic Preserve, and Olustee Battlefield Historic State Park; Osceola Wildlife Management Area; Osceola National Forest and Cary State Forest; and Big Gum Swamp Wilderness. In addition to providing important habitat for wildlife, these natural areas provi de ground water recharge, flood protection through the natural storage and detention of floodwaters, and the maintenance and enhancement of water quality.

The following table summarizes land use statistics calculated for the Nassau

- St. Marys Basin from

2004 Statewide Land Use imagery.

Land Use Agriculture Forest Urban Wetlands Other

Percentage 4 .2 4 9.9 5.9 33.1 6.9

The percentage reported as “Other” consists of water, rangeland, barren land, transportation, communication, and utilities.

## Monitoring Design of the Status Monitoring Network

FDEP has worked with the water management districts, local governments, and other entities to establish an Integrated Water Resource Monitoring (IWRM) Program. This program combines surface and ground water monitori ng efforts, consisting of water chemistry, biology, and sediment analyses. It is fiscally and logistically prohibitive to sample every river, stream, lake, or individual well in the state on a regular basis. A probabilistic monitoring design is a cost

- ef fective approach to produce a statistically valid estimate of the condition of water resources. The IWRM Program is made up of three levels of monitoring designs: (1) the Status Monitoring Network designed to

allow statistical inferences about all state waters; (2) more intensive basin monitoring used to identify and confirm impaired waterbodies that do not meet Florida’s water quality standards; and (3) site

- specific regulatory compliance monitoring.

The Status Monitoring Network uses a random site monitoring design to assess the state’s surface and ground water quality. The objective of this design is to broadly characterize aquatic resources with a known statistical confidence. Samples are collected from randomly selected points, which is

a cost

- effe ctive way to provide a geographic snapshot of the condition of all waters in a basin. This monitoring program is not designed to answer site

- specific questions about individual lakes, rivers, streams, or wells.

The Status Monitoring Network categorizes Florida’s fresh waters into 6 different resource types. Four of these are surface water: small lakes, large lakes, rivers, and streams. The other 2 resources are ground water: unconfined and confined aquifers. The 2004

– 09 Status Monitoring Network design divides the state into 29 basins, with 5 or 6 basins sampled each year. Approximately 30 samples are collected annually from each resource in the selected basins. Thus, in each basin, approximately 120 samples are collected for surface water resources, and 60 samples for ground water resources, in addition to quality assurance samples.



## Lakes

The Nassau

- St. Marys Basin has approximately 1 0 lakes. FDEP has divided these lakes by size into 2 categories: small lakes of 2.5 to 25 acres and large lakes over 25 acres. This division

allows a better characterization of the status of the basin’s lake resources. There are few natural

small lakes found in the basin.



## Rivers and Streams

The Nassau River, North Prong of the St. Mary’s River , and the St. Mary’s River, totaling 116 miles, represent the river resource. The remaining streams and tributaries are designated as the

stream resource. These total about 605 miles, although some may be dry during periods of drought. Both resources can have different habitats and uses.



## Aqu ifers

Aquifers are permeable layers of sand, gravel, or rock that contain water. Unconfined aquifers are near the land surface and are easily affected by human activities. Confined aquifers lie below a layer of material, such as fine

- grained clay, that limits the downward flow of water. Water in confined aquifers usually filters slowly through sediment and rock layers, and is older and less affected by human activities. FDEP’s Watershed Monitoring Section samples ground water in the

Nassau

- St. Marys Ba sin through wells in unconfined and confined aquifers.

There are three major aquifer systems present throughout the entire Nassau

- St. Marys Basin: the surficial aquifer system (SAS ), the intermediate aquifer system (IAS), and the Floridan aquifer
syste m (FAS). The SAS is the water table aquifer and is used as a potable water supply to a limited extent. The SAS is important in this watershed because it is the groundwater that directly interacts with surface waterbodies, providing base flow to streams, estuaries, and lakes. The IAS is composed of clays and acts mainly as a confining unit. The primary source of potable water in the basin is the FAS, which is deep, confined, and under artesian pressure throughout the area.

## Summary and Results

The tables below show the sampling carried out for each resource in the Nassau St. Marys Basin, in terms of acres of large lakes, number of small lakes, miles of rivers and streams, and number of wells for confined and unconfined aquifers. Not all randomly selected stations can be sampled for various reasons. Those that can be sampled are termed accessible. Those stations that cannot be sampled are considered either dry or inaccessible. Reduced rainfall or periods of drought occur on a cyclical basis in many areas of Florida. Prolonged or intense periods of drought can adversely affect water chemistry. During the sampling period

, precipitation was reduced by 11 % compared with the 30 -y ea r annual average.

Surface Water Resource Large Lakes ( ≥ 25 acres) Small Lakes (2.5– 25 acres) Rivers (3 rivers/canals) Streams (all other streams/ canals)

Resource Size (area, number, length) 2,874 acres 3 lakes 116 miles 605 miles

Accessible 100 % 67 % 46 % 20 %

Dry 0% 0% 0% 8%

Inaccessible 0% 33 % 54 % 72 %

Number of Samples 30 2 30 30

Ground Water Resource Unconfined Aquifers Confined Aquifers

Number of Wells 68 78

Accessible 50% 36 %

Inaccessible 50 % 64 %

Samples 29 28

Basin Precipitation Average Annual (1971

– 2000) Annual (200 7)

Nassau

- St. Marys Basin 51.7 inches 46.0 inches

Rainfall data were obtained from the National Climatic Data Center database for the Fernandina Beach and Glen St Mary 1 W Stations

. 

### The discussion and figures below provide results for the basin’s surface and ground water resources for a number of important indicators (see the Definitions and Criteria pages for explanations of the indicators used). As discussed in Definitions and Criteria , natural conditions such as higher water temperatures, freshwater and stormwater inflows, and different soil s can affect the results shown below. The exceedance of a standard or threshold is not necessarily caused by a pollutant.

Lakes : Dissolved oxygen (DO) is below the standard in 7% of the l arge lakes. Low DO can be harmful to aquatic life. Fecal coliform bacteria levels are within the standard for all large lakes. pH

is within the standard range for the large lakes. U n- ionized ammonia levels are within the standard

for all large and small la kes

. The Trophic State Index, a combined measure of nutrients and chlorophyll that indicates lake health, shows that 3 % of the large lakes sampled have excess nutrients and chlorophyll. There were not enough data to assess small lakes.

Rivers and Stre ams : DO is below the standard in 20% of the rivers and 87% of the streams sampled. Canal/ditch construction and ground water inflows can contribute to low DO concentrations. Low DO can be harmful to aquatic life. Fecal coliform bacteria are above the standard in 17% of the streams and within the standard for the rivers sampled. pH is outside the

### For more information, contact: Florida Department of Environmental Protection, Watershed Monitoring Section, MS 3525 2600 Blair Stone Road, Tallahassee, FL 32399 (850) 245

– 8433 ; http://www.dep.state.fl.us/wate r/monitoring/status.htm standard range for 47 % of the streams and within the standard for rivers

. Low pH occurs naturally

in blackwater streams

, which are numerous in this basin. Un

- ionized ammonia values are within

the standards for rivers and streams. Chlorophyll values are above the standard in 3% of the

rivers and 10% of the streams.

Aquifers : Exceedances of arsenic (3%), chromium (3%), a nd lead ( 10%) are found in a small percentage of the un confined wells. An exceedance for sodium (4%) was found in the confined

wells. Total coliform bacteria exceed the standard in 4 % of the confined wells and are within the

standard for unconfined wells . These bacteria are indicators of possible human health effects if the water is used for drinking. All other analytes are within standards.

Surface

Water

Resource Dissolved Oxygen Fecal Coliform pH Un

- ionized

Ammonia Trophic State

Index

Large

Lakes

Small

Lakes ISD ISD ISD ISD ISD

Surface

Water

Resource Dissolved Oxygen Fecal Coliform pH Un

- ionized

Ammonia Chlorophyll

Rivers

Streams

Ground

Water

Resource Arsenic Cadmium Chromium Lead Nitrate

– Nitrite Sodium Fluoride Total

Coliform

Unconfined

Wells

Confined

Wells

Note: The gray segments of the pie charts represent the percentage of water resources that meet s water quality standards. Blue segments represent the percentage that does not meet the standards. See the Definitions and Criteria pages for more information.

ISD: Insufficient data for analysis.



### This survey does not represent a comprehensive analysis of any individual waterbody.

The Watershed Monitoring Section would like to thank the St. Johns River Water Management

District for its contributions to this report.

## Surface Water Definitions and Criteria

Each indicator listed below was chosen because it has an applicable state criterion, found in Criteria for Surface Water Quality Classifications, Rules 62

- 302 and 62

- 303, Florida Administrative Code.

Indicators Criterion/Threshold 1 Designated Use

Fecal Coliform Bacteria < 400 counts/100mL Recreation Dissolved Oxygen ≥ 5 mg/L Aquatic Life pH ≥ 6 and ≤ 8.5 SU Aquatic Life

Un

- ionized Ammonia ≤ 0.02 mg/L Aquatic Life Chlorophyll a ≤ 20 μ g/L Aquatic Life Trophic State Index (TSI) Color ≤ 40 PCUs, then TSI ≤ 40 Color > 40 PCUs, then TSI ≤ 60 Aquatic Life

1 mL – milliliters; mg/L
– milligrams per liter; SU
– standard units; μ g/L
– micrograms per liter; PCUs
– platinum cobalt units

Fecal coliform bacteria : The single

- sample threshold for fecal coliform is 400 counts per 100 milliliters of water. These bacteria can enter water through the discharge of waste from mammals and birds, agricultural and stormwater runoff, and untreated human sewage. The presence of fecal coliform bacteria may indicate that the water is contaminated by other disease

- causing organisms.

Dissolved oxygen (DO) : T he state criterion for DO is a minimum of 5 milligrams per liter to maintain health y conditions for aquatic life. Lower levels do not affect human recreation. Algae and plants produce oxygen through photosynthesis. Oxygen is also dissolved in water by wind and wave action. Respiration by aquatic animals, decomposition, wastewater, stormwater runoff from urban streets or farmland, and failing septic tanks consume oxygen. Natural conditions

— such as ground water from springs, water from swamps/wetlands, higher water temperatures, and calm and cloudy weather

— can also decrease DO levels

i n waterbodies.

pH : The surface water criterion for pH is between 6 and 8.5 standard units. The pH scale, which ranges from 0 to 14, is a measure of the degree of acidity or alkalinity of a solution. Numbers below 7.0 indicate acidity; numbers above 7.0 indicate alkalinity. The midpoint of 7.0 on the pH scale represents neutrality

— that is, a neutral solution is neither acidic nor alkaline. pH affects many chemical and biological processes in water, and aquatic organisms are adapted to a certain range of pH. When pH levels are outside this range, it stresses these organisms’ physiological systems and can reduce reproduction. Atmospheric deposition (acid rain), geology, vegetation, and pollution can cause changes in pH.

Un

- ionized ammonia : The threshold for un

- ionized ammonia is less than or equal to 0.02 milligrams per liter. This is calculated from total ammonia and adjusted for temperature, salinity, and pH. Ammonia occurs in different forms; water temperature and pH affect which form predominates at any given time in an aquatic system. Un

- ionized ammonia can be toxic to fish and invertebrates.

Chlorophyll a* : The threshold for chlorophyll is less than or equal to 20 micrograms per liter. Chlorophyll is the pigment that allows algae and plants to convert sunlight into organic compounds during the process of photosynthesis. Excess nutrients, such as nitrogen and phosphorus, can stimulate algal blooms. Excess algae sink to the bottom and decay, using up the oxygen that other plants and organisms require to survive. High concentrations of chlorophyll reduce water clarity and limit the light available to shallow

- water ecosystems.

Trophic State Index (TSI)* : TSI and chlorophyll are the primary measures used to assess nutrient impairment in a waterbody. There are two thresholds for TSI, based on the color of a lake. Dark

- water lakes with a mean color greater than 40 platinum cobalt units (PCUs) are impaired when their annual mean TSI

exceeds 60. Clear and low

- color lakes with a mean color le ss than or equal to 40 PCUs are impaired when their annual mean TSI exceeds 40. TSI is measured using chlorophyll, nitrogen, and phosphorus

concentrations. A 10

- unit increase or decrease in the index represents a doubling or halving, respectively, of

the number of algal cells present.

________________________________ * Both TSI and chlorophyll a are not standards, but thresholds used to estimate the impairment of state waters. These thresholds are used in the analysis of Status Network data, based on single samples in a basin at a predetermined time of year. The analysis and representation of these data are not intended to infer the verification of impairment, as defined in Rule

62

- 303, Florida Administrative Code, in these waters.

## Aquifer Definitions and Criteria

The table below shows the thresholds for eight indicators regulated under drinking water standards.

Indicators Criterion/Threshold 1 Designated Use

Arsenic ≤ 10 μ g/L Potable Water(drinking water)

Cadmium ≤ 5 μ g/L Potable Water(drinking water)

Chromium ≤ 100 μ g/L Potable Water(drinking water)

Lead ≤ 15 μ g/L Potable Water(drinking water)

Nitrate

– Nitrite ≤ 10 mg/L Potable Water(drinking water)

Sodium ≤ 160 mg/L Potable Water(drinking water)

Fluoride ≤ 4 mg/L Potable Water(drinking water)

Total Coliform Bacteria (counts per 100 milliliters) ≤ 4 (sample maximum) Potable Water(drinking water)

1 μ g/L
– micrograms per liter; mg/L
– milligrams per liter

Arsenic, cadmium, chromium, and lead are all naturally occurring metals in the earth’s crust. These and other metals are used in manufacturing and can be produced and used in pesticides, preservatives, and industrial operations. They may enter water as a pollutant. Florida has primary standards (criteria) for these metals to protect human health. Excess levels in drinking water can cause adverse health effects.

Nitrate

– nitrite is used in fertilizer and is found in sewage and wastes from human and/or farm animals. Florida’s drinking water standard is 10 milligrams per liter (mg/L) for nitrate and 1 mg/L for nitrite. In addition, to allow for the fact that the toxicity of nitrate and nitrite is additive, the standard for the sum of nitrate and nitrite is 10 mg/L. In the long term, nitrates and nitrites have the potential to cause serious adverse effects in

humans.

Sodium (salt) has a drinking water standard to protect individuals who are susceptible to sodium

- sensitive hypertension or diseases that cause difficulty in regulating body fluid volume. Sodium is monitored so that

individua ls on sodium

- restricted diets may take the sodium in their water into account. Drinking water contributes only a small fraction (less than 10%) of an individual’s overall sodium intake.

Fluoride , a natural element, is added to drinking water systems to reduce dental cavities. Prolonged exposure to levels above 4 milligrams per liter may result in crippling skeletal fluorosis, a serious bone disorder. Lower levels may cause dental fluorosis when children are developing teeth. In its moderate and

severe forms, dental fluorosis is a brown staining and/or pitting of the permanent teeth.

Total coliform bacteria are common in the environment and are generally not harmful. The presence of these bacteria in drinking water, however, is an indicator that dise ase

- causing organisms may be present. The U.S. Environmental Protection Agency and Florida have set an enforceable drinking water standard for total coliform of 4 counts per 100 milliliters to reduce the risk of adverse health effects. Drinking water tha t meets this standard is usually not associated with a health risk from disease

- causing bacteria and is

considered safe.