Tracing runoff components in the headwater area of Heihe River by isotopes and hydrochemistry

Since water resources of the Heihe River Basin are primarily in the form of surface runoff in the Qilian Mountains, identifying its sources and components is essential for researchers to understand water cycling and transformation in the basin. It will help to properly exploit water resources, and contribute to ecological environment construction. The paper uses the isotope data of hydrogen and oxygen in water and hydrochemistry data collected at a high altitude to trace the sources of surface runoff in Heihe River in rainy season and uses the three-component mixing model to estimate the contribution of each component to runoff. Results indicate that surface water consists of precipitation, melt water and groundwater, with precipitation being the primary component and contributing to 59%–64% of runoff. Melt water and groundwater account for 15%–25% and 12%–22%, respectively. Precipitation accounts for 60%, groundwater for 22% and glacial melt water for 18% of the outflow in the main stream of the Heihe River. The composition is of great significance for water cycling and conversion research as well as water resource evaluation and management.