Water quality modelling

# Water quality modelling

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Encyclopedia
Water quality modeling involves the prediction of water pollution
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....

using mathematical simulation
Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...

techniques. A typical water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

model consists of a collection of formulations representing physical mechanisms that determine position and momentum of pollutants in a water body. Models are available for individual components of the hydrological system such as surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

; there also exist basinwide models addressing hydrologic transport and for ocean and estuarine applications. Often finite difference
Finite difference
A finite difference is a mathematical expression of the form f − f. If a finite difference is divided by b − a, one gets a difference quotient...

methods are used to analyse these phenomena, and, almost always, large complex computer models are required.

## Formulations and associated Constants

Water quality is modeled by one or more of the following formulations:
• Dispersive Transport formulation
• Surface Heat Budget formulation
• Dissolved Oxygen Saturation formulation
• Reaeration formulation
• Carbonaceous Deoxygenation formulation
• Nitrogenous Biochemical Oxygen Demand formulation
• Sediment oxygen demand formulation (SOD)
• Photosynthesis and Respiration formulation
• pH and Alkalinity formulation
• Nutrients formulation (fertilizers)
• Algae formulation
• Zooplankton formulation
• Coliform bacteria formulation (e.g. Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

)

• Hydrological transport model
Hydrological transport model
An hydrological transport model is a mathematical model used to simulate river or stream flow and calculate water quality parameters. These models generally came into use in the 1960s and 1970s when demand for numerical forecasting of water quality was driven by environmental legislation, and at...

s
• Volumes of water on earth
• Water resources
Water resources
Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water....

• Water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

• Wastewater quality indicators
Wastewater quality indicators
Wastewater quality indicators are laboratory tests to assess suitability of wastewater for disposal or re-use. Tests selected and desired test results vary with the intended use or discharge location. Tests measure physical, chemical, and biological characteristics of the...