Developing regional flow duration curves and evaluating the performances in the ungauged basins

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Civil Engineering, Turkey

Approval Date: 2011




A flow duration curve (FDC) defines the relation between the flow amount of any time (daily, yearly, or another time) and its frequency. Moreover, FDCs are used in many water resources projects. However, the ungauged basins or limited amount of gauging in a basin is a common problem. Therefore, regional FDCs are needed to be developed in ungauged basins. Oltu basin has been chosen as the study area, which is located in the north-eastern part of Turkey in Çoruh Basin. Two parametric approaches and a statistical approach have been applied to develop regional flow duration curves (FDCs) in Oltu Basin. Parametric approaches cover two different models, namely Model Kocatepe, which is a five parameter model depending on the regression analysis between discharge having certain probability of occurrences and geomorphologic and climatic factors; Model Quimpo, which is a two parameter model proposed by Quimpo. Lognormal distribution has been used in the statistical approach. Several performance indices have been evaluated to decide on if the model dependable or not. As a result of these analysis, it is concluded that, Model Quimpo gives good results in small basins, whereas, Model Kocatepe is effective in large areas. Statistical approach is not an appropriate method to use while regionalizing FDCs in Oltu basin.The analysis performed for short-term duration has revealed that 5-years record lengths of discharges are enough to develop a dependable FDC compared to regional FDC. The validation results and the performance indices are presented with the analysis results.