River Water Quality Monitoring

River Water Quality Monitoring in CWC


Central Water Commission is monitoring water quality at 390 key locations covering all the major river basins of India. CWC is maintaining a three tier laboratory system for analysis of the parameters. The level-I laboratories are located at 258 field water quality monitoring stations on various rivers of India where physical parameters such as temperature, colour, odour, specific conductivity, total dissolved solids, pH and dissolved oxygen of river water are observed. There are 23 level–II laboratories located at selected division offices to analyze 25 nos. physico-chemical characteristics and bacteriological parameters of river water.4 level-III/II+ laboratories are functioning at Varanasi, Delhi, Hyderabad and Coimbatore where 41 parameters including heavy metals/toxic parameters and pesticides are analysed.
The following procedure is followed in CWC for classification of stations, sampling frequency, identification of parameters and their analysis, which is based on Water Quality Assessment Authority’s Gazette Notification dated June 18, 2005.

(A) Classification

Stations are classified as Base, Trend and Flux Stations. CWC has 164 Base stations, 179 Trend stations and 28 Flux stations.

(B) Frequency of Monitoring

  • Base Station: One sample is collected every two months and totals six samples in a year.
  • Trend Stations: Sample is collected once in every month.
  • Flux Stations: Samples are collected thrice in a month, however toxic and trace metal are analyzed once in a month.

(C) Parameters

Level I Laboratory
4.Electrical Conductivity/ Total Dissolved Solids
6.Dissolved Oxygen

Level II Laboratory
2.Electrical Conductivity
4.Dissolved Oxygen
5.Biochemical Oxygen Demand (BOD)
6.Chemical Oxygen Demand (COD)
22.Total Plate count
23.Total Coliform
24.F. coliform
25.E. Coliform

Level II+III Laboratory
In addition to the parameters as indicated for level-II laboratory, the following additional parameters are analyzed.
26.Total Kjeldhal Nitrogen
28.Ammonia Nitrogen
29-34. Pesticides (6 nos.)
35. Total Organic Carbon
36-41.Toxic Elements
Arsenic, Cadmium, Mercury, Chromium, Lead, Zinc

River Water Pollution

A river is defined as a large natural stream of water emptying into an ocean, lake, or other body of water and usually fed along its course by converging tributaries. Rivers and streams drain water that falls in upland areas. Moving water dilutes and decomposes pollutants more rapidly than standing water, but many rivers and streams are significantly polluted all around the world. A primary reason for this is that all three major sources of pollution (industry, agriculture and domestic) are concentrated along the rivers. Industries and cities have historically been located along rivers because the rivers provide transportation and have traditionally been a convenient place to discharge waste. Agricultural activities have tended to be concentrated near rivers, because river floodplains are exceptionally fertile due to the many nutrients that are deposited in the soil when the river overflows.

Source of Pollution

Farmers put fertilizers and pesticides on their crops so that they grow better. But these fertilizers and pesticides can be washed through the soil by rain, to end up in rivers. If large amounts of fertilizers or farm waste drain into a river the concentration of nitrate and phosphate in the water increases considerably. Algae use these substances to grow and multiply rapidly turning the water green. This massive growth of algae, called eutrophication, leads to pollution. When the algae die they are broken down by the action of the bacteria which quickly multiply, using up all the oxygen in the water which leads to the death of many animals. Chemical waste products from industrial processes are sometimes accidentally discharged into rivers. Examples of such pollutants include cyanide, zinc, lead, copper, cadmium and mercury. These substances may enter the water in such high concentrations that fish and other animals are killed immediately. Sometimes the pollutants enter a food chain and accumulate until they reach toxic levels, eventually killing birds, fish and mammals. Factories use water from rivers to power machinery or to cool down machinery. Dirty water containing chemicals is put back in the river. Water used for cooling is warmer than the river itself. Raising the temperature of the water lowers the level of dissolved oxygen and upsets the balance of life in the water. People are sometimes careless and throw rubbish directly into rivers.

River Water Quality & Environmental Factors

River water quality is highly variable by nature due to environmental conditions such as basin lithology, vegetation and climate. In small watersheds spatial variations extend over orders of magnitude for most major elements and nutrients, while this variability is an order of magnitude lower for major basins. Standard river water for use as reference is therefore not applicable. As a consequence natural waters can possibly be unfit for various human uses, even including drinking. There are three major natural sources of dissolved and soluble matter carried by rivers: the atmospheric inputs of material, the degradation of terrestrial organic matter and the weathering of surface rocks. These substances generally transit through soil and porous rocks and finally reach the rivers. On their way, they are affected by numerous processes such as recycling in terrestrial biota, recycling and storage in soils, exchange between dissolved and particulate matter, loss of volatile substances to the atmosphere, production and degradation of aquatic plants within rivers and lakes etc. As a result of these multiple sources and pathways, the concentrations of elements and compounds found in rivers depend on physical factors (climate, relief), chemical factors (solubility of minerals) and biological factors (uptake by vegetation, degradation by bacteria). The most important environmental factors controlling river chemistry are:

  • Occurrence of highly soluble (halite, gypsum) or easily weathered (calcite, dolomite,pyrite, olivine) minerals
  • Distance to the marine environment which controls the exponential decrease of ocean aerosols input to land(Na+ , CI- , SO- , and Mg2+ ).
  • Aridity (precipitation/runoff ratio) which determines the concentration of dissolved substances resulting from the two previous processes.
  • Terrestrial primary productivity which governs the release of nutrients (C, N, Si, K).
  • Ambient temperature which controls, together with biological soil activity, the weathering reaction kinetics.
  • Uplift rates (tectonism, relief) Stream quality of unpolluted waters (basins without any direct pollution sources such as dwellings,roads, farming, mining etc).
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