R. Mirabbasi Najafabadi, Y. Dinpazhoh , A. Fakheri-Fard,
Volume 15, Issue 58 (winter 2012)
Abstract
Accurate estimation of runoff for a watershed is a very important issue in water resources management. In this study, the monthly runoff was estimated using the rainfall information and conditional probability distribution model based on the principle of maximum entropy. The information of monthly rainfall and runoff data of Kasilian River basin from 1960 to 2006 were used for the development of model. The model parameters were estimated using the prior information of the watershed such as mean of rainfall, runoff and their covariance. Using the developed model, monthly runoff was estimated for different values of runoff coefficient, , return period, , at different probability levels of rainfall for the basin under study. Results showed that the developed model estimates runoff for all return periods satisfactorily if the runoff coefficient value is taken 0.6. Also, it is observed that at a particular probability level and runoff coefficient, the estimated runoff decreases as return period increases. However, the rate of change of runoff decreases slightly as return period increases.
R. Samadi, Y. Dinpashoh, A. Fakheri-Fard,
Volume 27, Issue 3 (Fall 2023)
Abstract
A hydrological parameter affecting the management of water resource systems is changes in the amount and occurrence time of extreme precipitation (OTEP). In this research, the seasonality of precipitation in the Lake Urmia (LU) basin was analyzed using the daily extreme precipitation data of 30 rain gauges in the statistical period of 1991-2018. The uniformity of OTEP was tested by Rayleigh and Kuiper’s tests at 0.1, 0.05, and 0.01 levels. The slope of the trend line for OTEP was estimated using the modified Sen slope estimator. The uniformity of OTEP was rejected at each level. The results revealed two strong seasons: late winter and early spring (S1) and autumn (S2) for OTEP. The results showed a general median seasonality index of 0.3, which changed to 0.82 and 0.9 for S1 and S2, respectively, after dividing the whole year into two seasons. The seasonal strength of S1 was similar in both the western and eastern parts of LU, but the west of the lake was stronger than the eastern part in S2. In S1, negative and positive trends in the OTEP were observed on average in 40% and 60% of the stations, respectively, with corresponding values of 77% and 27% for S2, respectively.
