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Oklahoma Comprehensive Water Plan


Water Watch Volunteer FAQs

Why do we monitor water temperature?
Water temperature affects physical, biological, and chemical aspects of lake dynamics. High water temperatures stress aquatic ecosystems by reducing the ability of water to hold essential dissolved gasses like oxygen. The rate of decomposition, nutrient recycling, lake stratification, and dissolved oxygen concentration are all affected by the temperature. When a lake "mixes," cold water from the bottom of a lake (hypolimnium) is brought to the surface (epilimnion), while warm water is mixed downward, resulting in little temperature variation from top to bottom in the lake. Mixing allows dissolved oxygen to be introduced into the hypolimnium. When a lake stratifies, distinct temperature layers are formed, and the mixing of the water is restricted. The epilimnion (about the first 30 feet) warms the entire summer and continuously mixes, while the hypolimnion does not mix or get any warmer all summer. Shallow lakes (those less than 20 feet deep) usually will not stratify, and will continuously mix from top to bottom.

Why do we measure Dissolved Oxygen?
A good level of dissolved oxygen is essential for aquatic life. Dissolved oxygen analysis measures the amount of gaseous oxygen (O2) dissolved in an aqueous solution. Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a by-product of photosynthesis. Oxygen is a necessary element to all forms of life. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in large fish kills.

What is pH and why do we monitor it?
A vital determinant of a waterbody's health is its pH, which is a measure of the acidic or basic (alkaline) nature of a solution. The concentration of the hydrogen ion [H+] activity in a solution determines the pH. Fish and other organisms require a pH range of 6.5 to 9.0 in order to be viable.

What are "nutrients" and how do they affect the aquatic ecosystem?
In Oklahoma surface waters, Ammonia nitrogen, Nitrate nitrogen, and phosphorus are the chemical compounds most commonly referred to as "nutrients." These nutrients contribute to the growth of aquatic plants and algae. Excessive nutrient levels can cause plant and algal overgrowth, which can have a profound negative effect on the physical, chemical, and biological characteristics of a lake or stream. This process is known as eutrophication. Microscopic floating plants (algae) multiply rapidly when fertilized by phosphorus, and when the algae die, they decompose and the resulting bacteria cause all the dissolved oxygen to be removed from the water. Lower oxygen levels make it difficult for other aquatic organisms (fish and macro-invertebrates) to survive.

What is Cultural Eutrophication?
Cultural eutrophication occurs when humans cause an increase in the level of nutrients that are deposited into a lake. Cultural eutrophication can produce an anaerobic condition where oxygen in the water is completely depleted. This usually occurs near the bottom and produces gases like hydrogen sulfide, which causes a "rotten egg" smell. Cultural eutrophication causes a shift in aquatic life to a fewer number of species. These are replaced by other species that can tolerate low dissolved oxygen levels such as carp, midge larvae, and sewage worms (Tubifex). The effects of cultural eutrophication can be controlled by: reducing the use of lawn fertilizers (particularly inorganic forms) that drain into waterways, better farming practices, preserving natural vegetation near shorelines, preserving wetlands to absorb nutrients and maintaining water levels, treating storm sewer wastes, requiring particular industries to pre-treat wastes before sending them to a wastewater treatment plant.

What is turbidity and how is it measured?
Turbidity is a measurement of materials suspended in the water (such as algae or sediment) and is often an indirect indicator of the overall quality of the lake water. There are several methods in measuring turbidity, such as a turbidity tube, Secchi disc, or a turbidimeter. OWW volunteers use both the Secchi disc and the turbidimeter methods to determine turbidity. The OWRB uses a turbidimeter.

What is Chlorophyll and why do we monitor it?
Chlorophyll is the pigment found in all green plants that is responsible for their color. During photosynthesis, chlorophyll absorbs sunlight that is used as the energy source to convert carbon dioxide and water to oxygen and sugars. Chlorophyll data is collected because the green pigment is found in algae and can be used to estimate how much phytoplankton (floating algae) there is in the lake.


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Page last updated: August 12, 2004

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