Hydrology For Beginners Part 3 :

Test of Consistency/Estimation of Correct Rainfall and Approximation of Missing Rainfall Data

Test of Consistency/Estimation of Correct Rainfall

Double-mass analysis is used to determine the consistency of a rainfall record. This method compares station X's cumulative annual (or seasonal) values to those of a reference station. The reference station is typically the average of several nearby stations.

Here is a video walkthrough of the method: