Spatial analysis of Sr-90 artificial radionuclide in consequence of global fallout and Chernobyl nuclear accident has been carried out by using the point cumulative semivariogram (PCSV) technique based on 40 surface water station measurements in Keban Dam Lake during March, April, and May 2006. This technique is a convenient tool in obtaining the regional variability features around each sampling point, which yields the structural effects also in the vicinity of the same point. It presents the regional effect of all the other sites within the study area on the site concerned. In order to see to change of Sr-90, the five models are constituted. Additionally, it provides a measure of cumulative similarity of the regional variable, Sr-90, around any measurement site and hence it is possible to draw regional similarity maps at any desired distance around each station. In this paper, such similarity maps are also drawn for a set of distances. Sr-90 activities in lake that distance approximately 4.5 km from stations show the maximum similarity. (C) 2007 Elsevier Ltd. All rights reserved.