Determination of appropriate method for mapping rainfall and temperature with different probability levels in GIS environment and producing M. Turc runoff map: A case study in the Seyhan basin

This study was conducted in Seyhan River Basin, covering 21 470.3 km² area. Long term annual temperature and precipitation series were collected for meteorological observation stations, and rainfall-runoff data were collected from archives of research institutes and DSI. The aim of this study was to determine appropriate method for mapping rainfall and temperature with different probability levels in GIS environment and to produce M. Turc runoff map in the Seyhan river basin. The aim was also extended to compare the real-time flow measurements observed in research basins and in small earth dams located in the basin with M. Turc runoff estimates at those locations. Ordinary Kriging, Ordinary Cokriging and Multiple Regression techniques which consider the correlation amongst observations, geographical positions of meteorological stations and their distributions on the study area were utilized to produce temperature map with 50% probability level, and precipitation maps with 50%, 80% and 90% probability levels. By using minimum error criterion and also precipitation data observed at the critical locations where small earth dams were constructed, it was concluded that Multiple Regression and Ordinary Cokriging techniques were suitable for the purpose of mapping mean temperature with 50% probability level, and precipitation with 50%, 80% and 90% probability levels, respectively. Through using the suitable mapping techniques determined, M. Turc runoff maps with 50%, 80% and 90% probability levels were produced for Seyhan Basin. It was determined that M. Turc runoff values calculated in GIS media yielded more realistic results close to the observed runoff data in the basin, compared to M. Turc runoff values calculated conventionally. It was concluded that the A coefficient assigned to the Seyhan Basin was no longer representative, that a representative coefficient should be determined by an appropriate technique.Key Words: Seyhan Basin, GIS, Kriging, M. Turc, Runoff