Multiple Interpolations for different regions

For large or inhomogenious basins it can be neccessary to use different interpolation methods for different regions of the basin. Usually, an interpolation is done for the entire basin. To overcome this limitation, WaSiM allows the basin to be subdivided into regions with individual interpolations. This method does work for elevation dependent regression only (see below for other approaches).

Interpolation results in a transient band between two or three neighboring regions will be processed specially: Results of both/all three regions will be superpositioned depending on the distance to the respective region (see figure below).

The above approach only combines regression results of different regions. A new approach which overcomes all limitations is the so called regional superposition. The regions of the region grid are still used, but only in a second step. If, for instance, a region should be interpolated by IDW and regression, both methods will be called at first. The results of both interpolations are then input to the regional superposition. For each region and each interpolation result, a specific weight can be defined. The weighted sum of all interpolations defined for such a superposition is the final result used in the model later.

More details on multiple regression interpolations can be found in the document Interpolation of meteorologic Input Dataor in the WaSiM model documentaton

Sample for Weighting factors between neighboring regions