Prediction of Flow Duration Curve for Seasonal Rivers in Iraq

This paper presents a new method to estimate the flow duration curves [FDCs] for ungauged river basins whose natural and meterological characteristics are known. This study highlights the modeling of the lower three-quarters of the section of the flow duration curves [FDCs]. Eight sub-catchments were used to develop and evaluate the proposed flow duration model in the north of Iraq. The logarithmic type function has been found appropriate for the lower three-quarters of the section of [FDCs] for all river sub-catchments located in the study area. Parameter values of the logarithmic function model were calculated using topographic, hydrological and climatic characteristics of the basins under study by two regional regression models: first CA-MAP (catchment area-mean annual precipitation) model and second MAF-PE (mean annual flowpotential evapotranspiration) model. Generally, it is found that both models used were predicting a good estimate at the end of the flow duration curve (low-flows). In most cases, the statistics and graphical results showed that the agreement between observed and estimated FDCs is very good by using MAF-PE model as compared to CA-MAP model.