points should be consider while designing the RAIN-GAUGE station, DOUBLE MASS CURVE Technique

In this video i have explained the points should be consider while designing the RAIN-GAUGE station, how to find the optimum number of Rain-gauge station,what is average rainfall, normal rainfall and also how to check the continuity and consistency of rainfall data by using DOUBLE MASS CURVE Technique, how to find the missing rainfall data by using Arithmetic Mean method and Normal Ratio method.