Water quality has been an important issue as we move into the twenty-first century. Over the past 100 years more studies and research has been performed on rivers and streams than any other aspect of Environmental Engineering. From this research, it has been found that there are three important types of characteristics of river systems.

1. Physical Characteristics
   • geometry: width (b), depth (h)
   • river slope, bed roughness, "tortuosity"
   • velocity
   • flow
   • mixing characteristics (i.e river dispersion)
   • river water temperature
   • suspended solids & sediment transport

2. Chemical Characteristics
   • D.O. variations, including effects of oxidizable nitrogen
   • pH, acidity, alkalinity, relationships in areas subject to such discharges (i.e. mines & atmosphere)
   • total dissolved solids and chlorides in certain river systems
   • toxic chemicals

3. Biological Characteristics
   • bacteria & viruses
   • fish populations
   • rooted aquatic plants
   • biological slimes

Links to Important Modeling Equations

• Velocity
  
• Mixing Zones
  
• Conservative Point Source Discharge
  
• Nonconservative Point Source Discharge
  
• Distributed Nonconservative Source Discharge

• Rivers, hydrology
  
• National Park Service
  
• U.S. Army Corp of Engineers
  
• USGS
  
• Urban RIver Regeneration
  
• California Rivers Assessment (CARA)
  
• Save Our Streams
  
• Estuaries
  
• Watershed Studies