1. Introduction to surface water systems

Inland surface water systems such as rivers, streams, creeks, lakes, reservoirs, and wetlands play a hugely important role in our drinking water supply, agricultural irrigation, industrial utilization, recreational activities, and other public uses. Our everyday lives depend on the availability and quality of surface water. Surface water is in motion in response to natural forces, climatic effects, and human activities, all of which have a significant impact on its

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

quality. Although surface water systems are governed by many different factors, this chapter focuses primarily on two of the most influential aspects: hydrodynamics and water quality. Water's hydrodynamic characteristics include its flow velocity, water depth, and water surface elevation, while water quality is assessed in terms of its physical (temperature, color, odor, sediments, etc.), chemical (dissolved oxygen, salinity, organic matter and heavy metal content, nutrients, etc.), and biological characteristics (bacteria, viruses, protozoans, etc.). The interactions between the processes related to these characteristics are inevitably fairly complex; water system administrators must therefore seek to develop a good understanding of the dominant factors and processes that affect the water quality of each of the local water resources they are responsible for if they are to make correct or optimized management decisions.

of the San Joaquin River in California, to illustrate how these theoretical predictions compare to

Application of a Hydrodynamic and Water Quality Model for Inland Surface Water Systems

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Hydrodynamics deals with the motion of water and the forces acting on water. Hydrodynamic studies focus on investigating the mechanisms driving flow by quantifying the key physical processes in water. The results obtained provide invaluable information on the movement and transport of contaminants, which serves as the basis for all research into water quality. The information needed to develop a hydrodynamic model includes a comprehensive set of governing equations that describe the physical processes involved and the associated initial and boundary conditions required to numerically solve the equations, and the various param-

In hydrodynamics, the main property parameters of water are its density/specific weight and its viscosity, both of which have a significant impact on the solutions to the governing equations. The density of water can vary depending on the temperature, concentration of the suspended solids, and salinity. The influence of these factors on water density has been

where r<sup>T</sup> is the density of pure water as a function of temperature T [17, 18], Δr<sup>S</sup> is the change in density due to salinity S, and Δr<sup>C</sup> is the change in density due to total suspended sediments [19]. Viscosity represents the internal friction of water and is very important for hydrodynamic

Here, hydrodynamic processes refer to water motion, circulation, mixing phenomena; the corresponding processes involving the materials suspended in the water include advection, dispersion and mixing. The results combine to form a hydrodynamic model that generally includes flow field, water depth and water surface elevation, salinity, temperature, and sediment concentration. Some of this information, for example, which related to temperature,

The governing equations for both water flow and the transport of contaminants are based on the conservation laws of mass, momentum, and energy. Hydrodynamic models include two main types of governing equations: continuity equation for the mass balance of water in the

salinity, and/or sediment, may also be utilized in water quality models.

2.2. Cartesian coordinate-based governing equations

r ¼ r<sup>T</sup> þ Δr<sup>S</sup> þ Δr<sup>C</sup> (1)

/s) of a river can be approximated as a function of

<sup>υ</sup> <sup>¼</sup> <sup>1</sup>:<sup>785</sup> � <sup>0</sup>:0584<sup>T</sup> <sup>þ</sup> <sup>0</sup>:00116T<sup>2</sup> � <sup>0</sup>:0000102T<sup>3</sup> � <sup>10</sup>�<sup>6</sup> (2)

the hydrodynamic and water quality properties observed in real bodies of water.

2. Fundamentals of surface water hydrodynamics

eters that must be input to run the model.

processes. The kinematic viscosity (m2

formulated as follows [16]:

temperature T (�C) [20].

2.1. Water properties and hydrodynamic processes

Water quality is represented by the levels of a series of water quality parameters such as water temperature, dissolved oxygen, level of pathogens, and the concentrations of different chemicals, all of which may vary both temporally and spatially. In addition to the inactivation of contaminants, the levels and distribution of contaminants are governed by several dynamic processes, including diffusion, dispersion, and advection. These processes are closely linked to the water's flow characteristics, the influents and effluents entering and leaving the body of water, wind stress, the Coriolis effect (which must be taken into account in large bodies of water such as the Great Lakes), and stratified temperature, among other factors. In turn, the fate and transport of contaminants may influence flow, for example, sediment transport may change flow density. In addition to these common mechanisms shared by all surface water bodies, each will have its own unique characteristics. Therefore, to better understand how a particular surface water system functions, essential knowledge of its hydrodynamic and water quality related processes must be supplemented by information regarding its specific characteristics.

The methods typically used to study the surface water systems include theoretical analyses, mathematical modeling, laboratory experiments, and field observations. Experiments and observations are the most reliable ways to acquire real information for a specific system that will provide a good basis for analysis and modeling. However, for a complex surface water body, the observed or measured data are usually far from sufficient to reflect or predict a complete picture of the real scenario. Furthermore, the available data are not necessarily totally reliable, and low quality data with high errors may lead researchers to build a false or misleading idea of what is actually happening. Therefore, mathematical modeling coupled with observations for verification and calibration is essential in such cases. Hydrodynamic and water quality models have been widely developed and used for the investigations of rivers [1–4], lakes or reservoirs [5–11], estuaries [12, 13], and coastal waters [14, 15] on various aspects. These models have been effective tools for explaining, simulating, and forecasting the complex processes in water environment.

This chapter focuses on the fundamental concepts and principles of surface water analysis, and the application of a model that combines hydrodynamics and water quality. The goals are to help develop a better understanding of the different hydrodynamic processes involved to facilitate decision making in real surface water systems. After a discussion on the fundamentals of surface water hydrodynamics (Section 2), contaminant fate and transport in surface water and a water quality model will be discussed. This chapter concludes with a discussion of two case studies of very different surface water systems, the southern part of Lake Michigan and the upper reaches

of the San Joaquin River in California, to illustrate how these theoretical predictions compare to the hydrodynamic and water quality properties observed in real bodies of water.
