During the observation period, the volume-weighted mean values of *δ*^{18}O for streamflow at the catchment outlet, for the precipitation at the two sample sites, and for glacial meltwater were −11.9‰, −11.3‰, and −15.6‰, respectively. Calculations using the isotope hydrograph separation method, Equation (4), show that the contribution of glacial melt runoff to total runoff was 15.0%. Uncertainty results for hydrograph separation were shown in Table 1. Calculated by Equation (7), the uncertainty of the separation was ± 3.7% at the confidence level of 95%. Therefore, the contribution of glacial melt runoff was 15.0 ± 3.7% (the confidence level of 95%) at the Gaerqu River catchment. As the total runoff during the observation period was 2.55 × 10^{8} m^{3}, the glacial melt runoff can be calculated as (0.38 ± 0.09) × 10^{8} m^{3}.

Table 1

Samples . | Number of samples . | Weighted mean δ^{18}O (‰)
. | Standard deviation . | t (95%) . | Uncertainty (95%) . |
---|---|---|---|---|---|

Precipitation | 12 | −11.3 | 8.3 | 2.201 | 18.246 |

Glacier | 42 | −15.6 | 4.8 | 2.020 | 1.436 |

Streamflow | 24 | −11.9 | 0.7 | 2.069 | 9.740 |

Samples . | Number of samples . | Weighted mean δ^{18}O (‰)
. | Standard deviation . | t (95%) . | Uncertainty (95%) . |
---|---|---|---|---|---|

Precipitation | 12 | −11.3 | 8.3 | 2.201 | 18.246 |

Glacier | 42 | −15.6 | 4.8 | 2.020 | 1.436 |

Streamflow | 24 | −11.9 | 0.7 | 2.069 | 9.740 |

*Note:* 95% represents the confidence level.

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