Reservoir losses may be classified under following three heads.

  1. Evaporation losses
  2. Absorption losses
  3. Reservoir leakage or percolation losses.

1. Evaporation Losses.

  • These are the major losses from a reservoir.
  • This loss is affecte by expos surface area of the reservoir, wind velocity, temperature, relative humidity etc.
  • This loss is express in cm of water depth and varies from place to place depending upon the local conditions such temperatures, relative humidity, wind etc.
  • Average values of losses in cm for North and South India for various methods of the year are given as follows.


2. Absorption Losses.

  • This loss of water is considerable in the beginning, but falls to very small values after some time when pores get saturat.
  • These losses depend upon the soil forming the reservoir.
  • These losses are not consider while planning a reservoir.

3. Reservoir Leakage or Percolation Losses.

  • Reservoirs being very large, their banks are permeable.
  • But permeability of the soil is generally very low and hence these losses do not carry any importance.
  • But in certain cases the banks of the reservoir may be made of badly fractured rocks or having continuous seams of porous strata.
  • Such conditions may cause serious leakage.
  • To stop such leaks grouting with cement may have to be resort.
  • Hence while selecting the site of the reservoir, this aspect of the site is investigated in great length and if any such fault is noticed, it is rectified before reservoir is constructed