Water quality modeling involves water quality based data using mathematical simulation techniques. Water quality modeling helps people understand the eminence of water quality issues and models provide evidence for policy makers to make decisions in order to properly mitigate water. Water quality modeling also helps determine correlations to constituent sources and water quality along with identifying information gaps. Due to the increase in freshwater usage among people, water quality modeling is especially relevant both in a local level and global level. In order to understand and predict the changes over time in

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, climate change, and the economic factor of water resources, water quality models would need sufficient data by including water bodies from both local and global levels. A typical

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through ...

model consists of a collection of formulations representing physical mechanisms that determine position and momentum of

pollutants A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like o ...

in a water body. Models are available for individual components of the hydrological system such as

surface runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the ...

; there also exist basin wide models addressing hydrologic transport and for ocean and estuarine applications. Often

finite difference A finite difference is a mathematical expression of the form . If a finite difference is divided by , one gets a difference quotient. The approximation of derivatives by finite differences plays a central role in finite difference methods for t ...

methods are used to analyze these phenomena, and, almost always, large complex

computer model Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be det ...

s are required.

Building A Model

Water quality models have different information, but generally have the same purpose, which is to provide evidentiary support of water issues. Models can be either deterministic or statistical depending on the scale with the base model, which is dependent on if the area is on a local, regional, or a

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scale. Another aspect to consider for a model is what needs to be understood or predicted about that research area along with setting up any parameters to define the research. Another aspect of building a water quality model is knowing the audience and the exact purpose for presenting data like to enhance water quality management for

water quality law Water quality laws govern the protection of water resources for human health and the environment. Water quality laws are legal standards or requirements governing water quality, that is, the concentrations of water pollutants in some regulated vol ...

makers for the best possible outcomes.

Formulations and associated Constants

Water quality is modeled by one or more of the following formulations

* Advective Transport formulation * 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. ''

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'' )

SPARROW Models

A SPARROW model is a SPAtially-Referenced Regression on Watershed attributes, which helps integrate water quality data with landscape information. More specifically the

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

used this model to display long-term changes within watersheds to further explain in-stream water measurement in relation to upstream sources, water quality, and watershed properties. These models predict data for various spatial scales and integrate streamflow data with water quality at numerous locations across the US. A SPARROW model used by the USGS focused on the nutrients in the Nation's major rivers and estuaries; this model helped create a better understanding of where nutrients come from, where they are transported to while in the water bodies, and where they end up (reservoirs, other estuaries, etc.).

References

* U.S. Environmental Protection Agency (EPA). Environmental Research Laboratory, Athens, GA (1985)
"Rates, Constants and Kinetics Formulations in Surface Water Quality Modeling."
2nd ed. Document no. EPA/600/3-85/040. {{Refend

External links

SPARROW Water-Quality Modeling - US Geological Survey
US Geological Survey
BASINS
- EPA environmental analysis system integrating GIS, national watershed data, environmental assessment and modeling tools
Water Quality Models and Tools
- EPA
Models for Total Maximum Daily Load Studies
- Washington State Department of Ecology
Catchment Modelling Toolkit
-

eWater eWater is a non-profit organisation established by Australian Federal and State Governments. The role of eWater is to support integrated water resources management in Australia through development and implementation of the national hydrological mo ...

Cooperative Research Centre, Australia
Water Evaluation And Planning (WEAP)
an integrated water resources planning model, including water quality - Stockholm Environmental Institute (US)
Stochastic Empirical Loading and Dilution Model (SELDM)
- US Geological Survey stormwater quality model
U.S. Army Corps of Engineers Water Quality
- New water quality modeling software developed by the U.S. Army Corps of Engineers Environmental science Ecological experiments Aquatic ecology Chemical oceanography Environmental engineering

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