Impacts of gold mining and land use alterations on the water quality of central Mongolian rivers.

Abstract

Conservation of water quality is inherently tied to watershed management. Efforts to proect Lake Baikal have increasingly focused on the Selenge River, a major tributary, with more than half its watershed area in Mongolia. Placer gold mining in Mongolia has the potential to load total suspended sediment (TSS), and total phosphorus (TP) into Lake Baikal and destroy spawning areas for the endangered Taimen salmon (Hucho taimen taimen). This work describes water quality assessments performed from 2001 to 2003 on Mongolian tributaries to the Selenge River. Of 7 rivers sampled, rivers with proximal mining had the worst water quality. Elevated loading of TSS and TP was observed below mining regions on the Tuul River. Flooding could breach thin strips of land separating dredge pits from river channels, resulting in massive sediment loading. Extensive disturbance of the river terrace was apparent for many square kilometers. In the mountainous headwaters of the Yeroo River, tributary drainages undergoing mining had TP concentrations 8 to 15 times higher than the main stem. TSS was 7 to 12 times higher, and turbidity was 8 times higher. Alternative mining technologies exist that could minimize impact and improve the possibility for reclamation.