Characterization of Water And Water Bodies

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How is the characterization of Water bodies done? The characterization is done by classification into three major components:

  1. Hydrology
  2. Physical-chemistry
  3. Biology.

 Water quality assessment is based on the appropriate monitoring of the above three components. 

Hydrodynamic features

The hydrological cycle inter-connects all freshwater bodies from the atmosphere to the sea. The different stages of water ranging from rainwater to marine salt waters make the water constitute a continuum. The inland freshwaters form parts of the hydrological cycle and they appear in the form of rivers, lakes, or ground-waters. 

These principal types of water bodies are closely interconnected. These forms may influence each other in a direct manner, or through intermediary stages. Each of the three forms has distinctly different hydrodynamic properties.

Rivers are primarily characterized by the unidirectional flow of current. This is accompanied by a relatively high, average flow velocity ranging from 0.1 to 1 metre per sec. The river flow is supposed to be highly variable in time, based on the climatic situation as well as the drainage pattern. 

Thorough and continuous vertical mixing is achieved in rivers as a result of the prevailing currents as well as turbulence. Lateral mixing may happen only over longer distances downstream of major confluences of the water body.

Lakes are primarily characterized by a low, average current velocity of 0.001 to 0.01 metre per sec. To quantify mass movements of material, one can use water or element residence times, ranging from one month to several hundreds of years. Currents

within lakes are found to be multi-directional. Many lakes experience alternating periods of stratification as well as vertical mixing; the periodicity of which is regulated by climatic conditions as well as lake depth. 

Ground-waters are primarily characterized by a rather steady flow pattern in terms of direction as well as velocity. These are largely governed by the porosity as well as the permeability of the geological material. This results in poor mixing and, based on local hydrogeological features, the ground-water dynamics can be extremely diverse. 

There are multiple transitional forms of water bodies. These water bodies demonstrate features of more than one of the three basic water body types mentioned above. These water bodies are characterized by a specific combination of hydrodynamic features. The most important transitional water bodies are listed as below:

  1. Seas and oceans
  2. Lakes and reservoirs
  3. Swamps and marshes
  4. River channels
  5. Soil moisture
  6. Ground Water
  7. Icecaps and glaciers
  8. Atmospheric Water
  9. Biospheric Water
  10. Fluxes
  11. Evaporation from oceans
  12. Evaporation from land
  13. Precipitation from oceans
  14. Precipitation from land
  15. Run-off to oceans
  16. Glacial ice

Alluvial and karstic aquifers are considered to be intermediate between rivers and ground-waters. The flow regime is rather slow for alluvial and very rapid for karstic aquifers (also referred to as underground rivers).

As a result of the range of flow regimes noted above, large variations in water residence times happen in the different types of inland water bodies. The hydrodynamic characteristics for each type of water body are primarily dependent on the size of the water body as well as on the climatic conditions prevailing in the drainage basin. The hydrological regime (discharge variability) of the rivers form the governing factor for rivers.

Lakes are normally classified by their water residence time as well as their thermal regime resulting in varying stratification patterns.

Some reservoirs share many features similar to lakes. Some other reservoirs have characteristics that are specific to the origin of the reservoir. One feature that is common to most of the reservoirs is the deliberate management of the inputs and/or outputs of water for particular purposes. Ground-waters majorly depend upon their recharge regime (infiltration) through the unsaturated aquifer zone. This allows for the renewal of the ground-water body.

Reservoirs are primarily characterized by features which are intermediate between the characteristics of rivers and those of lakes. The reservoirs can range from large-scale impoundments to small dammed rivers. They have a seasonal pattern of operation and water level fluctuations. Read More