Abstract
In this research, the main aim is to formulate a mathematical model describe the relationship between annual probable maximum precipitation (PMP) for the city of Najaf and other hydrological variables such as temperature, relative humidity and evaporation rates depending on hydrologic data for the period between 1980 to 2005. All the calculations of the values of annual probable maximum precipitation were made depending on Hershfield's method, which is depended on the general equation of hydrologic frequency analysis and calculating the frequency factor for a group of data. The model was derived by the help of the program (SPSS 21).The study demonstrated a relative correlation between the previous independent variables, as a group, and the dependent variable (PMP) in one hand and the correlation between each independent variable with the value of PMP in the other hand. The coefficient of determination (R2) obtained from the statistical analysis for four equations were derived for each case with very suitable values.
Highlights
The rainfall is one of the hydrological factors that affected by other weather factors and the variation in its values occurred according to the change in season and geographical location of the area
The study examined the correlation between the amount of annual rainfall as the dependent variable and some weather variables and other climate independent variables, study showed the importance of the variables studied and their impact on the amount of rainfall in
The study showed that the area of cases of persistent drought for the last seven years for a period of data recording rates have fallen much annual rainfall rates for the public, which is due to the phenomenon of global warming being witnessed by the world in general and the region in particular
Summary
The rainfall is one of the hydrological factors that affected by other weather factors and the variation in its values occurred according to the change in season and geographical location of the area. The distribution of extreme values type 1 (EV1) of rainfall and all the results are compared with the values of PMP with duration of one day which are calculated from the method of Hershfield (1961). They show the difference between the method of Bethlahmy and Hershfield in one hand and the method of synoptical in the other. Paimozd (2002) suggested a new method for estimation PMP by combining the synoptical and statistical methods at eastern basins of Hormozgan province in Iran. A mathematical model are derived to describe the relationship between the value of PMP and other hydrological factors for Al-Najaf Al-Ashraf province in Iraq for the period between 1980 to 2005.
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