Hydrological Risk Assessment of Gibe III Dam by Using L-Moment

Sintayehu Yadete Tola

doi:10.11648/j.ajwse.20190501.14

Abstract

A hydrological analysis for assessing the risk of dam overtopping is required for both dam designing and dam safety checking. There is enormous amount of water to be stored in the reservoir to provide valuable service such as hydroelectric power generation and flood control. However dams can cause catastrophic damage to both life and property if they experience performance failures due to overtopping and inadequate spillway design. The hydrological risk was computed from historical peak flow data of Gilgel Gibe near Abelti, Gojeb near Shebe and Wabi near Wolkite, of major rivers flowing towards Gibe III Dam, respectively. From the flood statistics of rivers, the general extreme value (GEV) distribution was fitted to peak flow using L-moment. In this research made an attempt, the extreme event or probability of maximum discharge occurrence at dam site analyzed by associating peak occurrence with the service life of Dam and estimated the hydrological risk at Gibe III Dam. It finds PWM method is very suitable for three river flow condition flowing toward Gibe III Dam. The hydrological risk at Gibe III predicted for 50, 100 and 150 years with respect of Discharge range of 2730m3/s to 3180m3/s was observed there is a risk decreases as return period increases.

Highlights

Flood frequency analysis and determining the design flood are the main objectives of hydrological analysis and are the basis for design of hydraulic structures and management of water resource [1, 2, 3]
Gibe at Abelti of observed data is slightly closer to three rivers, this might be due to the catchment area which is more than 70% of as compared to the total of three catchments area
The hydrological risk was computed by summing up the historical peak flow data of Gilgel Gibe near Abelti, Gojeb near Shebe and Wabi near Wolkite, of major rivers flowing towards Gibe III Dam, respectively

Summary

Introduction

Flood frequency analysis and determining the design flood are the main objectives of hydrological analysis and are the basis for design of hydraulic structures and management of water resource [1, 2, 3]. Dams and Reservoirs are mainly constructed to store surplus water in wet season which can be used during dry season when the natural flow is inadequate to meet the demands. Reservoirs and dams play an essential role in controlling and harvesting benefits from floods and always pose potential risks to human life and property on their downstream side in the event of flood [4, 5, 6]. An exact estimate of flood design and extreme inflow hydrographs is required for the design of such important hydraulic structures [7]. The proper design of a dam’s spillway and the flood control capacity of a reservoir can ensure the safety of a dam and avoid any undesirable problems such as overtopping

Methods

Findings

Discussion

Conclusion