摘要
Drinking water supplies in Ulaanbaatar, the capital of Mongolia, are completely dependent on groundwater sourced from pumping wells located in an alluvial plain of the Tuul River which flows through Ulaanbaatar. The interaction between groundwater in the alluvial plain and river surface water was investigated using a hydrological and multi-tracers approach. The observed groundwater contour map clearly shows that the Tuul River recharges the floodplain groundwater and groundwater flows from east to west. The similarity of chemical and stable isotopic compositions suggests that groundwater is mainly recharged by Tuul River water in the vicinity of the river. In addition, considering groundwater contours and chemical composition, groundwater in the northern and southern mountain sides contribute to floodplain groundwater. Stable isotopic information suggests that winter season precipita- tion also contributes to the groundwater, because groundwater in a specific region has a considerably lower isotopic ratio. Using the End Member Mixing Analysis applying oxygen-18, SiO2 and HCO3 as tracers, the contribution ratios of the Tuul River, groundwater in the northem and southern mountain regions, and winter season precipitation to floodplain groundwater are esti- mated to be 58% to 85%, 1% to 54%, 0% to 16%, and 0% to 12%, respectively.
Drinking water supplies in Ulaanbaatar, the capital of Mongolia, are completely dependent on groundwater sourced from pumping wells located in an alluvial plain of the Tuul River which flows through Ulaanbaatar. The interaction between groundwater in the alluvial plain and river surface water was investigated using a hydrological and multi-tracers approach. The observed groundwater contour map clearly shows that the Tuul River recharges the floodplain groundwater and groundwater flows from east to west. The similarity of chemical and stable isotopic compositions suggests that groundwater is mainly recharged by Tuul River water in the vicinity of the river. In addition, considering groundwater contours and chemical composition, groundwater in the northern and southern mountain sides contribute to floodplain groundwater. Stable isotopic information suggests that winter season precipita- tion also contributes to the groundwater, because groundwater in a specific region has a considerably lower isotopic ratio. Using the End Member Mixing Analysis applying oxygen-18, SiO2 and HCO3 as tracers, the contribution ratios of the Tuul River, groundwater in the northem and southern mountain regions, and winter season precipitation to floodplain groundwater are esti- mated to be 58% to 85%, 1% to 54%, 0% to 16%, and 0% to 12%, respectively.
基金
part of the UNESCO-Chair on Sustainable Groundwater Management in Mongolia
financially supported by UNESCO/Japan Funds-in-Trust Co-operation for the Promotion of International Cooperation and Mutual Understanding.
