Key Station Network Method
One of the most rational methods for determination of key station is as suggested by Hall (1972).
In this method, at first, the correlation coefficient between the average of storm rainfall and the
individual station rainfall are found. The stations are then arranged in the order of their decreasing
correlation coefficients and the station exhibiting highest correlation coefficient is called the
first key station and its data is removed for determination of next key station. The procedure is
repeated by considering the average rainfall of the remaining stations. The station showing the highest
correlation coefficient after removing the data of first key station is called the second key station.
Similarly third and successive key stations are determined after removing the data of already selected
key stations. Now the sum of the squares of deviations of the estimated values of average rainfall
from the actual rainfall in respect of 1st, 2nd, 3rd key station etc. is determined and a graph is
plotted between the sum of the square of deviation and corresponding number of stations
in combinations. It will be seen that a stage comes when the improvement in the sum of squares of
deviation is very little with the addition of more stations. The corresponding number of
stations at that stage is taken to be representative and key stations for the network in the catchment/ basin.