The estimation of average areal rainfall by percentage weighting polygon method in Southeastern Anatolia Region, Turkey

The percentage weighting polygon (PWP) method is proposed as an alternative to the Thiessen method for calculating the average areal rainfall (AAR) over a given catchment area. The basis of the method is to divide the study area into subareas by considering the rainfall percentages obtained at three adjacent station locations. This method is more reliable and flexible than the Thiessen polygon procedure where the subareas remain the same, independent of the measured rainfall amounts. In this paper, the PWP method is applied to the Southeastern Anatolia Region of Turkey for the first time by considering 10 meteorological stations. In PWP method, higher rainfall values are represented with the smaller subareas than in the case of the Thiessen and the other conventional methods. It is observed that the PWP method yields 13.5% smaller AAR value among the other conventional methods.