Safe Yield, Secondary Yield And Design Yield

(i) safe yield

  • It is also known as firm yield.
  • It is the maximum quantity of water that can be supplied from the reservoir with full guarantee during the worst dry period.

(ii) secondary yield

  • The quantity of water available in excess of safe yield is known as secondary yield.
  • This yield is available during period of high inflows.
  • This secondary yield of the reservoir can be used either to generate extra hydroelectric power or for irrigation of extra lands.

(iii) design yield

  • The critical period for a reservoir is generally considered, when natural flow in the reservoir is minimum.
  • There is possibility that sometimes the minimum natural flow in the reservoir may even fall short of guaranteed yield.
  • Hence a lower value than the guaranteed yield or safe yield may be taken for design purpose.
  • This yield whose value is smaller than the safe or firm yield is known as design yield.
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