2. Fundamentals of surface water hydrodynamics

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

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

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

responsible for if they are to make correct or optimized management decisions.

complex processes in water environment.

88 Applications in Water Systems Management and Modeling

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 parameters that must be input to run the model.
