Definitions of Term and Their Significance in Capacity of Hydro Power Plant

1. Hydrology :
System related with water in termed as hydrology. It relates with mass of water, head of water, flow of water (Quantity). From the above data the work that water can do can be calculated, which can be utilized to decide upon the installed capacity of hydro power stations.
2. Surface Run off :
It is that portion of precipitation which makes its way towards streams, lakes or oceans. Run-off can be possible only when the rate of precipitation exceeds the rate at which water infiltrates into the soil and after small and large depressions on the soil surface get filled up with water. Also losses due to evaporation have be deducted. In general the run-off is given by
R = P – E
where, R = Run-off, P = Precipitation, E = Evaporation
3. Evaporation :
It is the transfer of water from liquid to vapour state.
4. Precipitation :
This includes all the water that falls from atmosphere to the earth surface. It is mainly of two types :
(i) Liquid precipitation (Rainfall)
(ii) Solid precipitation (Snow, Hail)
5. Significance of these on capacity of power plant :
As we have seen previously, Run-off = Precipitation – Evaporation, where precipitation represents all the water fall from atmosphere to earth surface and evaporation is conversion of water in vapour due to atmospheric variations. Hence we are able to know the quantity of water available stored) in a dam or lake, which can be used for production of hydro-power. Also knowing the head of water and quantity of water that will be available per/sec. or per/hr. etc. can be calculated, then using Bernoulli’s equation power in kw is determined, which decides the installed capacity of plant.