An integrated approach for detection and delineation of leakage path from Micro-Dam Reservoir (MDR): a case study from Arato MDR, Northern Ethiopia

Water is at the center of all efforts to address food security, poverty reduction, economic growth, energy production and human health. In arid and semi-arid regions, groundwater and water harvesting structures (such as Micro-Dam Reservoirs, MDRs) play a significant role for irrigation and maintaining the sustainability of water resources. Fighting poverty and drought using construction of MDRs is becoming a common practice in Tigray (northern Ethiopia), but their implementation is not without challenges. Reservoir leakage, inter alia, is one of the main problems facing MDRs in the region. This paper presents geological, geophysical, hydrogeological and hydrochemical study results in MDR to better understand and delineate leakage zones and mechanisms. Conventional geological mapping, geo-electrical methods (VES and ERP), hydrogeological and geochemical methods were used to understand the geological and geo-hydrological situation of the MDR. Integrated interpretation and synthesis of the data enable to delineate the leakage zone and path. The limestone-shale-marl intercalation unit that makes up the foundation and reservoir area is found to be the leaky unit due to syngenetic and epigenetic discontinuities, while the dolerite unit is relatively impervious. Installation of a cut-off wall at the upstream toe of the dam could be a possible solution to minimize the leakage problem underneath the dam foundation and left abutment/flank. As an alternative, proper utilization of the water from big diameter shallow hand dug wells from the leakage zone downstream of the MDR may be also conceived as a target without incurring additional costs of maintenance.