BASIN: The land area that drains into water body, the term is used interchangeably with 'watershed'. Basins are drained by a group of interconnected waterways, called tributaries, which flow into a larger waterbody. For example there are numerous tributaries (Little Pottsburg Creek, Red Bay Branch, Silversmith Creek, etc.) in the Arlington River basin that flow into the Arlington River.

Dissolved Oxygen Pie Chart

Dissolved oxygen (D.O.) is usually expressed as milligrams per liter (Mg/L) or Parts Per Million (PPM). Dissolved oxygen is a good indicator of overall water quality in most situations. Oxygen enters the water from the atmosphere and through aquatic plant and phytoplankton photosynthesis. The oxygen is then available for aquatic organisms to utilize in basic metabolic processes. Most aquatic animals can grow and do well when the dissolved oxygen level exceeds 5 mg/l. A drop in the level to 3-5 mg/l causes organisms to become stressed. Levels below 3 mg/l cause death in many species. One common cause of dissolved oxygen depletion is the breakdown and decomposition of organic materials in the water. This organic material may originate from many sources, such as nutrient-rich urban and agricultural runoff, wastewater treatment facility discharges, and algae blooms, which themselves may have been caused by excess nutrients. Natural sources of organic material in our surface waters are primarily from aquatic and wetland vegetation. Some aquatic systems with otherwise good water quality exhibit naturally low dissolved oxygen concentrations, particularly creeks that drain swamps. The state of Florida's standards for D.O. is 5.0 mg/l for fresh water and 4.0 mg/l for marine waters.

The area where the fresh water rivers meet and mix with the salt waters of the ocean. The lower St. Johns River extends from Mayport here in Jacksonville upstream approximately to Palatka and is considered an estuary for that entire 100-mile distance.

Fecal Coliform Bacteria Pie  Chart


Fecal coliform bacteria are bacteria that inhabit the intestinal tract of humans and warm-blooded animals. The State uses fecal coliform bacteria as an indicator of fecal pollution, which may come from, pets, wildlife and human sewage carried to the waterways by stormwater runoff. Human sources of fecal coliform bacteria enter the St. Johns River through breaks or malfunctions in the sanitary sewer system and failing septic tanks. The fecal coliform bacteria themselves are not harmful; they are used to indicate the possible presence human pathogens that do present a human health threat. If the fecal coliform bacteria concentrations are high in recreational waters and are ingested while swimming or enter the skin through a cut or sore, the associated pathogens may cause human disease, infections or rashes. The water quality standard established by the state of Florida for a 'one time' sample is: fecal coliform shall not exceed 800 colonies per 100 milliliters. When concentrations exceed 800 the waterbody is failing to meet it's designated use for recreation, and contact can present a risk to human health.

This value is the average of the previous four quarters measurements.

The submerged area of a water body along the shorelines. In the St. Johns River this area often inhabited by submerged aquatic vegetation. Littoral zones serve as nursery and feeding areas for numerous forms of aquatic life.

The primary channel of the river, the Buckman Bridge crosses over the 'mainstem' of the St. Johns River.

For surface water quality consideration nutrients include: ammonia (NH3), nitrites and nitrates (NO2&NO3), total kjeldahl nitrogen (TKN), total phosphorus (TP) and ortho-phosphorus (OP), all generally measured in milligrams per liter (Mg/L). Nutrients are chemicals required for plant growth, however they can become a serious problem when levels become elevated. Algae blooms are often the result, which in turn can lead to, dissolved oxygen depletion and reduced transparency of the water. Sources of nutrients are varied and include: storm water runoff containing fertilizer components from yards, agricultural runoff and treated sewage from wastewater plants or septic tanks.

A geographic location where samples are collected and water quality measurements are made.

Salinity Rating Pie Chart
A measure of the degree of salt content in the waterbody usually expressed in Parts Per Thousand (PPT). Drinking water is less than 0.5 PPT and ocean water is typically greater than 35 PPT. Salinity is one of the primary factors that determine what type of plants and animals live in a waterbody. For State surface water quality standards waterbodies are considered 'Fresh' when salinity is below 2.7 (PPT) and 'Marine' when greater than 2.7 PPT.

Total Maximum Daily Load or TMDL is estimated amount or 'loading' that a water body can assimilate of a certain type of pollutant and still meet the water bodies 'designated use'. The St. Johns River is classified as a 'Class III' water body, summarized as suitable for 'recreation, propagation and maintenance of a healthy well-balanced population of fish and wildlife'. A TMDL based on dissolved oxygen and water transparency needs is under development for the lower St. Johns River. Nutrients are the primary factor influencing these two water quality parameters.

A naturally occurring waterway that flows into a larger waterway. For example Little Pottsburg Creek in Arlington is a tributary to the larger Arlington River which in turn is a tributary to the St. Johns River.

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For more information contact:

Ambient Water Quality Section
Environmental Quality Division
407 North Laura Street, Third Floor
Jacksonville, FL 32202
(904) 255-7100