Spatial Correlation Method

Under the assumption that spatial variability of rainfall can be quantified through a spatial correlation function, a network of raingauges can be designed to meet a specified error criterion (Kagan, 1966 and WMO, 1972). However in applying such an approach, care must be taken to ensure that condition necessary for the existence of spatial correlation function, such as hydrological homogeneity and isotropy are fulfilled; flat areas with a relatively homogeneous surface are more appropriate for the application of the technique. A general theoretical spatial correlation method for the planning of meteorological networks has been given by Gandin (1970). Some details of the specific approach and its application have been given by Kagan (WMO, 1972). The basis of this method is the correlation function ρ(d) which is a function of the distance between the stations, and the form of which depends on the characteristics of the area under consideration and on the type of precipitation. The function ρ(d) can frequently be described by the following exponentiam form: