Geological, geophysical and engineering geological investigation of a leaky micro-dam in the Northern Ethiopia
Abstract
The study was conducted to assess the main causes of leakage problem in the Hashenge micro-dam, located in the Tigray regional state, northern part of Ethiopia. The micro, dam is a 19 m height earth fill dam with the length of 387 m and reservoir capacity of about 2.3 million cubic meters at maximum water level. Geological, geophysical and engineering geological investigations were conducted in the abutment and reservoir area to assess and pinpoint the main causes. The dominant lithologic units include limestone-shale-marl intercalation, dolerite and recent soil deposits. Vertical electrical sounding was used to locate geotechnical boreholes and to know vertical and lateral variability of geological materials. Geotechnical and engineering geological investigation including drilling of three boreholes and packer testing along with detail measurement and analysis of discontinuity parameters was conducted. Analysis of the data showed that the sedimentary succession, limestone-shale-marl intercalation was the leaky unit and responsible to the water harvest failure of the scheme. The hydraulic conductivity of the leaky unit was estimated from packer test results and discontinuity data in the order of 10-3 m/s. This study revealed that detail subsurface investigation in cyclic sedimentary sequence should be a critical prerequisite in water harvesting planning.
Keywords: boreholes, Ethiopia, Hashenge, micro-dam, reservoir, Tigray
Citation: Berhane G. Geological, geophysical and engineering geological investigation of a leaky micro-dam in the Northern Ethiopia. Agric Eng Int: CIGR Journal, 2010, 12(1): 31-46.
