Paper Information

Journal:   IRANIAN JOURNAL OF AGRICULTURAL SCIENCES (JOURNAL OF AGRICULTURE)   2006 , Volume 37 , Number 2; Page(s) 361 To 369.
 
Paper: 

AN EVALUATION OF THE IMPACT OF EL NINO - SOUTHERN OSCILLATION (ENSO) ON STREAMFLOW AND HYDROLOGICAL DROUGHT (WET) IN FARS PROVINCE

 
 
Author(s):  NAZEM ALSADAT S.M.J.*, RAHIMI MORTEZA, KESHAVARZI A.R.
 
* FACULTY OF AGRICULTURE, UNIVERSITY OF SHIRAZ
 
Abstract: 
The impact of El Nino - Southern Oscillation (ENSO) phenomenon on stream flow of five rivers (Kor, Roodbal, Gare-Aghaj, Mond, and Sheshpir) in Fars province (Iran) during the period 1957-2000was investigated. The warm (El Nino), cold (LaNina),and neutral(without El Nino and La Nina) phases of ENSO were defined and time series of monthly streamflow in each phase were constructed (these time series are generally known as ENSO-streamflow composites). For every of the constructed composites the amounts of 33, 50 and 67 percentiles were determined. The ratio of these percentiles in El Nino and La Nina phases to the corresponding values during neutral periods was calculated and used as a criterion for the evaluation of the impact of warm and cold phases of ENSO on streamflow. The results indicated that, for most of the year, the occurrence of El Nino causes a considerable increase in the considered river flow. For instance, as compared to neutral period, the spring and summer discharges of Gare-Aghaj river increase by about 120%during warm ENSO phase. For the other sites the increase rate varied from about 10% to 60%. The occurrence of La Nina generally causes the increase and decrease in streamflow in winter and the rest of the year, respectively.
The most considerable decrease (about 50%) was observed in Gare-Aghaj and Roodbal in spring and summer. The intensity of hydrological drought during El Nino and La Nina (except for winter) periods was found to be lower and higher than that during the neutral periods, respectively. In contrast, the probability of hydrological wet during El Nino and La Nina periods was observed to be more, and less than that during the neutral periods, respectively.
 
Keyword(s): DROUGHT, HYDROLOGIC, FARS, ENSO, EL NINO, RIVER
 
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