## 2 Data and Methods
### Data Resources and Methods  
For this study, we used a combination of meteorological, hydrological, cryospheric, and socio-economic data. We used daily air temperature and precipitation measurements, collected between 1961 and 2015, from seven national meteorological stations located on the southern edge of the Altai Mountains that were operated by the China Meteorological Administration (CMA). In the data processing process, the monthly average or annual average temperatures are obtained by the arithmetic average, but the monthly and annual precipitation are obtained by summing daily precipitation. Monthly discharge measurements spanning the period 1957-2015 were obtained from two national hydrological stations, i.e., Kuwei station in the headwaters of the Irtysh River Basin and Kelatashi station in the western part of the SAM. The monthly water level of Ulungur Lake between 1992 and 2016 was obtained from the Hydrology Reconnaissance Bureau (HRB) of Altay Prefecture, China. The locations of the meteorological and hydrological stations used in this study are shown in Figure 1 and Table 1.  
The cryospheric data included the observations of snow cover, SFG, river ice, and glaciers. The daily snow thickness and SFG depth during the cold season (October-April), snow cover and SFG durations, and soil temperature at 40-cm depth were monitored synchronously with the weather conditions by CMA. The timing of river ice formation and breakup was observed by HRB during the period 1981-2013, with the river ice thickness measured every 10 days. The glacier information was derived mainly from the First and Second Chinese Glacier Inventories, which were completed in the 1960s and 2000s, respectively.  
The socio-economic datasets were obtained from the Yearbook of Social and Economic Statistics (YSEC) from Xinjiang Uygur Autonomous Region of China, Water Resources Bulletin (WRB) of Xinjiang Uygur Autonomous Region of China, and the Annual Economic Report (AER) of Chinese Altay Prefecture ([[http://www.xjalt.gov.cn/sjalt/dataalt.html](http://www.xjalt.gov.cn/sjalt/dataalt.html)]([http://www.xjalt.gov.cn/sjalt/dataalt.html](http://www.xjalt.gov.cn/sjalt/dataalt.html)), accessed on 17 November 2021). The population and demographic composition, and regional gross domestic product (GDP) between 2007 and 2016 were derived primarily from the YSECs, and the water resources availability and consumption date for the same period were obtained from the WRBs. The hydropower production and energy consumption, and agricultural planting structure between 2017 and 2019, were obtained from the AERs.  
In the data processing process, the monthly average or annual average temperatures are obtained by the arithmetic average of daily average data, but the monthly and annual precipitation are obtained by summing daily precipitation.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Site Type** & **Station Name** & **Longitude** & **Latitude** & **Elevation (m)** & **Data Range** \\ \hline \multirow{8}{*}{Meteorological stations} & Habahe & 48.05\({}^{\circ}\) & 86.40\({}^{\circ}\) & 532.6 & 1961–2015 \\  & Jimunai & 47.43\({}^{\circ}\) & 85.87\({}^{\circ}\) & 984.1 & 1961–2015 \\  & Buerjin & 47.70\({}^{\circ}\) & 86.87\({}^{\circ}\) & 473.9 & 1961–2015 \\  & Fuhai & 47.12\({}^{\circ}\) & 87.47\({}^{\circ}\) & 500.9 & 1961–2015 \\  & Altay & 47.73\({}^{\circ}\) & 88.08\({}^{\circ}\) & 735.3 & 1961–2015 \\  & Fuyun & 46.98\({}^{\circ}\) & 89.52\({}^{\circ}\) & 807.5 & 1961–2015 \\  & Qinghe & 46.67\({}^{\circ}\) & 90.38\({}^{\circ}\) & 1218.2 & 1961–2015 \\ \hline \multirow{2}{*}{Hydrological stations} & Kuwei & 47.36\({}^{\circ}\) & 89.66\({}^{\circ}\) & 1375.0 & 1957–2015 \\  & Kelatashi & 48.22\({}^{\circ}\) & 89.45\({}^{\circ}\) & 590.0 & 1957–2015 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Information of meteorological and hydrological stations used in this study.