The classical solid/liquid distribution coefficient, K-d, for radionuclides in water-sediment systems is dependent on many parameters such as flow, geology, pH, acidity, alkalinity, total hardness, radioactivity concentration, etc. in a region. Considerations of all these effects require a regional analysis with an effective methodology, which has been based on the concept of the cumulative semivariogram concept in this paper. Although classical K-d calculations are punctual and cannot represent regional pattern, in this paper a regional calculation methodology is suggested through the use of Absolute Point Cumulative SemiVariogram (APCSV) technique. The application of the methodology is presented for Cs-137 and Sr-90 measurements at a set of points in Keban Dam reservoir, Turkey. (C) 2009 Elsevier B.V. All rights reserved.