Undai river diversion project in Oyu Tolgoi
Bazardorj, Sod-Erdene; Purevsuren, Uuganbayar
Oyu Tolgoi LLC, Mongolia
Oyu Tolgoi is copper and gold mining project located in gobi desert region of Mongolia. Oyu tolgoi open pit operation was to affect Undai dry river bed which is inseparable part of gobi desert ecosystem and it sustains drinking water points for local habitants. Thus subsurface and surface flows of Undai dry river bed was diverted from its main course away from impact zone of open pit and rejoined to its former flow by relocating new spring at the edge of Mine Lease area. Undai river diversion system consists of diversion dams, flood water diversion channel and subsurface flow diversion.
Upon completion of construction work in 2013, long term comprehensive environment monitoring was conducted in term of water level, water laboratory analysis, flow rate, flood monitoring and observations. Water quality was improved at the New Bor ovoo spring fresh water by complying potable water standard parameters with TDS range of 200-300 ppm. Measured flow rate range was 0.4 – 2.4 L/s depending on summer-autumn rain events. No adverse impact on herders’ shallow groundwater wells and local water courses in downstream of the diversion structure have been identified as per datalogger measurement of boreholes’ water level.
Heavy floods occurred due to the rainfall in 2017-2018 summers passed through the flood water diversion channel and reached further original downstream without affecting open pit operation. Wide range of endemic as well as domestic animals recorded in the camera trap. Undai river diversion project successfully completed based on multi-year environment monitoring data and it’s been accepted with local government and herders. Also the project has been in the attention of international organizations such as International Finance Corporation, Compliance Advisor Ombudsman and received favorable feedbacks.