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|Title:||IMPACT OF ENSO ON RIVER FLOWS IN GUYANA|
|Authors:||Mishra, Vidayshree Diana N.|
|Abstract:||The El Nino Southern Oscillation (ENSO) phenomenon is a natural part of the global climate system resulting from the interactions between large-scale ocean atmospheric circulation processes in the equatorial Pacific and Indian Oceans. It refers to a seesaw shift in surface air pressure at Darwin, Australia and the South Pacific Island of Tahiti. When the pressure is high at Darwin it is low at Tahiti and vice versa. The effects of the Southern Oscillation (SO) are pervasive, but strong responses are found only in limited portions of the tropics. El Nino, and its sister event La Nina are the extreme phases of the Southern Oscillation, with El Nino referring to a warming of the eastern tropical Pacific, and La Nina a cooling. There is also a neutral phase during the transition between the two phases. ENSO affects the hydro-climate of tropics especially in South America and bring higher than average rainfall in some areas and draught in others. In view of this and to study the effect of ENSO on streamflows, flow data of three rivers in Guyana namely the Demarara, Essequibo and Mazaruni were analysed in conjunction with the three ENSO indices namely SOI, MEI and i (JMA). Among the three rivers, the Demarara exhibits the highest variations in the annual flow series. There are relatively fewer lower than average flow values while there are relatively more of the lower than average flow values for the Essequibo and Mazaruni Rivers. The general behavior of the median and the mean of the flows during the La Nifia phase are usually higher than those of the El Niflo and Neutral phases. Overall the Demarara River seems to have a stronger relationship with the ENSO indices than the Essequibo and Mazaruni Rivers. iv Hypothesis tests of association between the ENSO indices and river flows show relatively stronger associations when divided into the ENSO phases. Low streamflow is associated with El Nino; it is positively correlated to the SOI and negatively correlated to MEI. Although the correlations between river flows and the three ENSO indices are weak, there is marked tendency for lower than average discharges during the El Nino years and higher than average discharges during the La Nina years. The MEI gives higher correlations with the flows of all three rivers than the other two indices. The results of ANOVA and Kruskall-Wallis tests show that the mean of the three ENSO phases are significantly different at 95% confidence level for the three rivers. It means the association between the river flows and the ENSO indices varies from river to river. There may be factors like location, local hydro-climatology etc. influencing the degree of effect of ENSO. Further investigation considering these factors is the subject of future research. Since the flow data of the rivers follow behavioral patterns in relation to the southern oscillation, it is concluded that ENSO has some bearing on the stream flows of Guyanese rivers. v|
|Appears in Collections:||MASTERS' DISSERTATIONS (Hydrology)|
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