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Accueil du site → Doctorat → États-Unis → 2006 → Characterizing the severity of hydrologic droughts

COLORADO STATE UNIVERSITY (2006)

Characterizing the severity of hydrologic droughts

Tarawneh, Zeyad Salem

Titre : Characterizing the severity of hydrologic droughts

Auteur : Tarawneh, Zeyad Salem

Grade : Doctor of Philosophy (PhD) 2006

Université de soutenance : COLORADO STATE UNIVERSITY

Résumé
This dissertation concerns with research on multiyear droughts that may occur in a given river system. One may obtain drought properties from the observed streamflows of a river under consideration, however that information is limited and uncertain because of the typical short sample sizes that are generally available. The main objective of this research is to characterize the severity of multiyear droughts. Mathematical models are developed to determine the return period and risk of droughts. A drought of a given length l occurs where a consecutive number of deficits persists over the time period l. Drought deficits have been fitted using the beta distribution. The drought risk has been determined assuming that the first occurrence probability of drought is geometric. Furthermore, expressions to determine droughts return period have been developed. The results obtained from the referred models have been verified using simulation experiments based on streamflows of the Poudre, Colorado, and Niger rivers. It is concluded that the models developed provide fairly good estimates of drought properties. In addition, the referred models have been extended to characterize regional droughts. It is concluded that the proposed models give fairly good estimates of regional drought properties. Tree ring indices have been utilized to reconstruct streamflows. A multivariate regression model (MREXTN) was developed in such a way that streamflow characteristics are properly taken into account. The proposed model was tested against competing models using simulation. It is concluded that model MREXTN compares favorably versus alternative models. Furthermore, the model was applied to reconstruct flows at the Colorado River system. It has been shown that the reconstructed flows provide useful information that enables one to analyze drought properties more accurately than using historical records alone.

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