# The Influence of Glacier Mass Balance on River Runoff in the Typical Alpine Basin
## 4 Discussions
### Influence of GMB on River Runoff  
Glaciers are in a negative GMB state, and their melting has increased, increasing glacier runoff. The annual average runoff in the Tailan River Basin was 2.99 \(\times\) 10\({}^{8}\) m\({}^{3}\) from 2000 to 2022, and the runoff showed a sharp decrease after 2000. Compared to 2000, the runoff decreased by 2.71 \(\times\) 10\({}^{8}\) m\({}^{3}\) in 2009, with a 63% decrease. After 2009, the runoff in the Tailan River basin increased; especially from 1.56 \(\times\) 10\({}^{8}\) m\({}^{3}\) in 2009 to 4.06 \(\times\) 10\({}^{8}\) m\({}^{3}\) in 2010, there is an increase of 61%. Based on the conclusions in Section 3.2 of this paper, the average GMB in the Tailan River basin from 2000-2009, 2009-2022, and 2000-2022 was \(-\)0.34 \(\pm\) 0.05 m w.e.a\({}^{-1}\), \(-\)0.19 \(\pm\) 0.10 m w.e.a\({}^{-1}\), and \(-\)0.30 \(\pm\) 0.02 m w.e.a\({}^{-1}\), respectively, with water equivalent values of 1.56 \(\times\) 10\({}^{8}\) m\({}^{3}\), 6.89 \(\times\) 10\({}^{7}\) m\({}^{3}\), and 1.38 \(\times\) 10\({}^{8}\) m\({}^{3}\). As shown in Table 8, the average annual runoff in the entire Tailan River basin from 2000-2009 was 2.84 \(\times\) 10\({}^{8}\) m\({}^{3}\), with a water equivalent of 1.56 \(\times\) 10\({}^{8}\) m\({}^{3}\) from glacier meltwater, accounting for 54.92% of the glacier meltwater supply. From 2009-2022, the glacier meltwater in the basin decreased by 8.71 \(\times\) 10\({}^{7}\) m\({}^{3}\) compared to 2000-2009, with an average annual runoff reduction of 1.39 \(\times\) 10\({}^{8}\) m\({}^{3}\). Figure 11: The relationship between glacier elevation and aspect. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Year**} & **Mass Balance** & **Glacier Meltwater** & **Annual Average Runoff** & **Rate** \\  & **(m w.e.a\({}^{-1}\))** & **(m\({}^{3}\))** & **(m\({}^{3}\))** & **(\%)** \\ \hline
2000–2009 & \(-\)0.34 \(\pm\) 0.05 & 1.58 \(\times\) 10\({}^{8}\) & 2.84 \(\times\) 10\({}^{8}\) & 54.92 \\
2009–2022 & \(-\)0.19 \(\pm\) 0.10 & 6.89 \(\times\) 10\({}^{7}\) & 1.45 \(\times\) 10\({}^{8}\) & 47.76 \\
2000–2022 & \(-\)0.30 \(\pm\) 0.02 & 1.38 \(\times\) 10\({}^{8}\) & 2.99 \(\times\) 10\({}^{8}\) & 46.15 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Contribution rate of glacier meltwater to runoff in Tailan River basin. Figure 12 shows the relationship between runoff and precipitation in the Tailan River basin. Over the past 22 years, the annual average temperature in the Tailan River basin has shown a slight upward trend, with an increasing rate of 0.08 \({}^{\circ}\)C-a\({}^{-1}\). In contrast, there has been a significant reduction in the total annual precipitation, with a decreasing rate of \(-3.2\) mm\(\cdot\)a\({}^{-1}\). During all three periods, glacier meltwater accounted for over 40% of the total runoff, with a higher contribution observed from 2000-2009 compared to 2009-2022. This trend may be related to the increasing temperature and decreasing precipitation levels. The rise in temperatures inhibits precipitation, making the snow and ice melt faster, which increases the contribution of glacier meltwater. The result found that the contribution rate of glacier melt water to runoff in the eastern and central Tianshan Mountains is between 3.5% and 67.5% [77]. It can be seen that glacier meltwater is very important for surface runoff recharge. The paper conducted a Mann-Kendall analysis on the Tailan River basin to observe changes in runoff, and explore abrupt changes in the flow regime since 2000. As shown in Figure 13, the M-K test curve revealed that the UF curve showed a decreasing trend between 2007 and 2010, while the curve increased and surpassed the lower confidence limit of \(\alpha=0.05\) in 2009-2010. The UB curve did not exceed the above limits except from 2014 to 2016. Notably, the UF and UB curves intersected at three points (2000-2002, 2010-2015, and 2020-2022), indicating abrupt changes in runoff. Nevertheless, the UF curve did not significantly exceed the confidence level during these periods.