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RMIT University (2019)

A methodology to assess hydrological drought events

DISSANAYAKE MUDIYANSELAGE Chandi Shakila Mimrose

Titre : A methodology to assess hydrological drought events

Auteur : DISSANAYAKE MUDIYANSELAGE Chandi Shakila Mimrose

Université de soutenance : RMIT University

Grade : Doctor of Philosophy (PhD) 2019

Résumé
The limited availability of streamflow data restricts the direct use of hydrological drought indices for drought assessment. Hydrological drought is a progression of meteorological drought. Therefore, the development of a hydrological drought forecasting methodology based on widely available rainfall data will be useful. This study focuses on the development of a simplified measurable relationship between the drought characteristics of meteorological and hydrological droughts. The concept of catchment hydrological response to rainfall fluctuation is used to predict hydrological droughts. A total of 30 catchments with undisturbed streams in the lower Murray Darling Basin are used in this study. First, the catchments are divided into three main homogenous regions using the hierarchical clustering method, followed by Andrews curves, since the hydrological response differs in different regions. The rainfall-based Standardized Precipitation Index (SPI) and streamflow-based Standardized Hydrological Drought Index (SHDI) are used to calculate meteorological and hydrological drought respectively. Monthly rainfall and streamflow data from 1900 to 2010 period are used for the calculations. Since streamflow data recording started only in the 1960s - 1970s, the Australian Water Balance Model (AWBM) is calibrated and used to simulate past streamflow data from 1900 to 1970 in the studied catchments with actual rainfall and evapotranspiration data. The parallel meteorological and hydrological drought events are identified on the SPI and SHDI time series. The drought events are then categorized into four drought classes : mild, moderate, severe and extreme, depending on the severity of the event. Multiple linear regression is used to identify the relationship between meteorological and hydrological droughts, SHDI being the dependent variable, and SPI and 14 catchment climate and physiographic characteristics being the independent variables. Regression equations are developed for extreme, severe and mild drought classes for different homogeneous regions idetified by a catchment regionalization process. These equations show that different homogenous regions have different sets of catchment characteristics as the most important variables. The developed equations can be used to predict the intensity and magnitude of possible hydrological droughts in ungauged catchments.

Mots clés : Hydrological drought Meteorological drought Catchment characteristics Regression equations Australian Water Balance Model Water Resources Engineering Civil Engineering not elsewhere classified

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