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Drainage: 9th CBSE Social Science

Question: What is river pollution? What are the factors causing river pollution? Explain them.

Answer: Water pollution is the pollution of bodies of water, such as lakes, rivers, seas, the oceans, as well as groundwater. It occurs when pollutants reach these bodies of water, without treatment. Waste from homes, factories and other buildings get into the water bodies.

Water pollution is a problem for the species and ecosystems there. It affects plants and organisms living in the water. In almost all cases the effect is damaging not only to individual species and populations, but also to the wider biological communities. The color is usually green or brown but normal water can be blue.

Causes of Water Pollution: Water pollution is caused due to several reasons. Here are the few major causes of water pollution:

  1. Sewage And Waste Water: Sewage, garbage and liquid waste of households, agricultural lands and factories are discharged into lakes and rivers. These wastes contain harmful chemicals and toxins which make the water poisonous for aquatic animals and plants.
  2. Dumping: Dumping of solid wastes and litters in water bodies causes huge problems. Litters include glass, plastic, aluminum, Styrofoam etc. Different things take different amount of time to degrade in water. They affect aquatic plants and animals.
  3. Industrial Waste: Industrial waste contains pollutants like asbestos, lead, mercury and petrochemicals which are extremely harmful to both people and environment. Industrial waste is discharged into lakes and rivers by using fresh water making the water contaminated.
  4. Oil Pollution: Sea water gets polluted due to oil spilled from ships and tankers while traveling. The spilled oil does not dissolve in water and forms a thick sludge polluting the water.
  5. Acid Rain: Acid rain is pollution of water caused by air pollution. When the acidic particles caused by air pollution in the atmosphere mix with water vapor, it results in acid rain.
  6. Global Warming: Due to global warming, there is an increase in water temperature. This increase in temperature results in death of aquatic plants and animals. This also results in bleaching of coral reefs in water.
  7. Eutrophication: Eutrophication is an increased level of nutrients in water bodies. This results in bloom of algae in water. It also depletes the oxygen in water, which negatively affects fish and other aquatic animal population.

Question: Measures to avoid water pollution.


  1. DO NOT pour fat from cooking or any other type of fat, oil, or grease down the sink. Keep a “fat jar” under the sink to collect the fat and discard in the solid waste when full.
  2. DO NOT dispose of household chemicals or cleaning agents down the sink or toilet. Simsbury has a Hazardous Waste Collection day usually from 8:00am to 1:00pm at Henry James School. Connecticut Resource Recovery Authority lists all collection dates.
  3. DO NOT flush pills, liquid or powder medications or drugs down the toilet. For recommendations on proper disposal for all types of medical wastes, visit the CT DEP publication here.
  4. Avoid using the toilet as a wastebasket. Most tissues, wrappers, dust cloths, and other paper goods should be properly discarded in a wastebasket. The fiber reinforced cleaning products that have become popular should never be discarded in the toilet.
  5. Avoid using a garbage disposal. Keep solid wastes solid. Make a compost pile from vegetable scraps.
  6. Install a water efficient toilet. In the meantime, put a brick or 1/2 gal container in the standard toilet tank to reduce water use per flush.
  7. Run the dishwasher or clothes washer only when you have a full load. This conserves electricity and water.
  8. Use the minimum amount of detergent and/or bleach when you are washing clothes or dishes. Use only phosphate free soaps and detergents.
  9. Minimize the use of pesticides, herbicides, fertilizers. DO NOT dispose of these chemicals, motor oil, or other automotive fluids into the sanitary sewer or storm sewer systems. Both of them end at the river.
  10. If your home has a sump pump or cellar drain, make certain it does not drain into the sanitary sewer system. If you are unsure, please call Sims-bury Water Pollution Control at (860) 658-1380 and we can assist in determining the discharge point.

Question: Differential between Deltas and Estuaries.


  1. A river delta is a triangular river mouth with several branches, side flows and bayous. The delta is formed by the silt and terrain carried by the river flow along the river, and it little by little lengthens the flow of the river towards the sea.
  2. An estuary is a river mouth which resembles a funnel and which widens, deepens and opens toward the sea. An estuary is formed by a tidal bore, which ablates the riverbed and carries the silt out to sea.
  3. The rule of thumb is that where there is a noticeable tide, the rivers form estuaries: where there is little or no tide, rivers form deltas. All European rivers which flow to Atlantic (tide present) have estuaries, such as Thames, Tojo, Loire, Seine, Rhine or Elbe. Those rivers which flow to Mediterranean (no tide), such as Tiber, Nile, Po or Ebro, form deltas.
  4. Deltas are extremely fertile, and most civilizations of the old have formed along river valleys and deltas. Estuaries make excellent harbors and fisheries, and many important port towns are located on estuaries.

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