Table 2. Statistics and T-test in runoff for the three time intervals at the Kaqun Station of the Yarkand River (unit: 10⁸ m³).

Time stages	Average annual runoff (108 m3)	Standard deviation	Standard error mean	Sig. (two-tailed)	95% Confidence interval of the difference
					Lower	Upper
1970–1992	64.91	10.95	2.28	0.00	60.17	69.64
1993–2004	68.12	12.10	3.49	0.00	60.43	75.81
2005–2017	73.93	11.43	3.17	0.00	67.02	80.84