• Any reservoir cannot last for ever.
  • Ultimately all the reservoirs get silted up.
  • Silting of the reservoir starts from the day it is created.
  • When reservoirs are created some of its capacity is left unused.
  • This is the capacity of the reservoir lying below the crest level of the bottom most under sluices.
  • This storage capacity which remains unused is know dead storage.
  • This dead storage capacity is used to accommodate deposited silt so that effective storage of the reservoir is not affected.
  • So long as dead storage capacity of the reservoir is not silted completely, effective storage or useful storage capacity is not affected.
  • The process of silting continues even after complete silting of dead storage.
  • The further silting affects the effective storage of the reservoir and the reservoir does not have enough water to fully fulfil its obligations.
  • Generally useful life of the reservoir is considered terminated when its effective storage is reduced by 20% of the designed capacity of the reservoir.

Density currents.