SURFACE WATER RESOURCES AND THEIR WATER QUALITY

  

SURFACE SOURCES

Surface water resources includes three types of sources

1) Lakes and Streams
2) Rivers
3) Storage Reservoirs

1) LAKES AND STREAMS


A natural lake is a large water body in the land. A lake is used to supply water to its nearest areas. The runoff of water that goes in the lake should be measured correctly and it should be equal to the demand of that area people. Streams are made by the surface. Streams have plenty of water in rainy season but the flow of water in dry season is quite low and it may cause the streams dry. 

The catchment area of both lakes and streams is low. So, the water supply is also low in these water bodies. Therefore, they cannot be used as water supply schemes for large cities. They can only be used for nearby areas and small towns. 

Water Quality
The water of lakes and streams is free from impurities. This water can be utilized safely for drinking water purpose. 

2) RIVERS


Rivers proves as the large source of water supply schemes for Rivers are classified into two categories. Some rivers are perennial that flows throughout the seasons because these are snow fed rivers. Other rivers are Non Perennial rivers that became dry in hot seasons and floods face the rivers in monsoon seasons. It is necessary to utilize the flood water by storing the water in winter through constructing dams and utilize this water in summer. 

The river water can be used for the following purposes:

  • source of water supply for a town
  • used for navigation
  • source of water supply for irrigation
  • used for purification of waste
  • source of recreation activities such as bathing, boating and fishing etc.
Quality of Water



The quality of river water is not consistent. It has silt and suspended impurities. When sewage water (partially or completely treated) is entered into river, then high contamination in rivers is observed. The river water should be analyzed in the perspective of diseases, bacteria and high impurities. River water should be effectively treated before its use as drinking water. Quality of water changes depends upon many parameters such as catchment area, sewage discharges, climate conditions and season of year. The quality of river water is found good at its head and it turns to deteriorating by reaching at its coarse areas. 

Reasons why River Pollution Undesirable

  • Contamination of water leads to increase in pressure on treatment units
  • Effects on fishes life
  • Hindrance of recreational use
  • Hindrance in navigation
  • Irritation by odor and appearance of river water
3) STORAGE RESERVOIRS

An artificial lake made by the construction of dam across a valley is known as storage reservoir. It has three parts:

1) A dam to store water
2) spillway to promote excessive flow of water
3) Gate Chamber having valves to regulate the water flow

These reservoirs present a source of water for large cities. The reservoir water can be used for irrigation and power generation. 

Site Selection for Reservoir

Following points should be considered while selection of a site:
  • land area to be submerged by reservoir construction
  • availability of construction materials
  • elevation of reservoir level
  • availability of skilled labor
  • water quality in reservoir
  • water availability
  • properties of catchment area
  • density of population over catchment area
  • good foundation bed for dams