No abstract

In this research, the effect of random component in the modified Thomas-Fiering model to generate daily rainfall data was studied, and Akre station considered a case study. A random component with special distributions: Normal random numbers, Wilson-Hilferty (W-H) transformation, truncated W-H, and Kirby modification to W-H transformation were used. The model applied to the daily rainfall data for Akre station for available years 2000–2006 and the model used to generate the rainfall data for the years 2006 and 2007. The results showed that the correlation coefficients between the observed and generated data were 0.82 for normal random numbers, 0.77 for W-H transformation, 0.89 for truncated –W –H, and 0.87 for KM to W-H transformation. The tests of Chi-square test, Kolmogorov–Smirnov test, root mean squared error (RMSE) test, and mean absolute error (MAE) test were used to compare between observed and generated data. All the results have passed the Chi-square test and Kolmogorov–Smirnov, where the calculated values were less than the tabulated value at 5% significance. For the test RMSE and MAE, the truncated W-H transform was the values of at least two. Therefore, W-H transform is the best for generating the rainfall data at Akre station

In any hydrologic study, the most important parameter is the runoff which is necessary for designing any hydraulic structure, and for determining the risk of flood. As there is a scare in the availability of runoff data in many sites, hydrologists have developed indirect methods to determine the runoff to accelerate the program of watershed management for conserving and developing water resources management. Many methods are used to estimate the runoff; Soil conservation curve number (SCS-CN) method is widely used and gives a reliable result compared with other methods. The present study aims to calculate the surface runoff depth depending on the SCS-CN method using a Geographic information system (GIS). For this Gali-Bandawa watershed in Duhok, north of Iraq has been selected, the geographical area of this watershed is about 92Km2 and the average annual rainfall is around 620mm, the weighted CN is 76. The results show that the depth of annual average runoff for the Gali-Bandawa watershed is 70mm, and the average volume of runoff from the same watershed is 6470360 m3. The amount of runoff represents 11.4% of the total annual rainfall. This approach could be applied in other Iraqi's watersheds for the planning of various conservation measures.