## 4 Results
### Air Temperature Analysis in the Varzob River Basin
The winter period in the lower reaches of the river is not very severe and the two remaining months of winter are December and February. The spring-autumn period practically does not cause sharp jumps in temperature. Assessing the temperature values by years at Anzob station in the upstream region, we can say that the predominance of sub-zero temperatures is clearly visible on the graphs and the relative minimum is below zero (Figure 3). General temperature monitoring for the period 1990-2018 showed that the trend line is in the mode of stable sub-zero temperatures. Additionally, small temperature spikes in 1998 and 2006, when the temperature jumped out of the zero mark, showed us relative anomalous years. Figure 2: The mean monthly air temperature in the upstream, midstream, and downstream regions in the Varzob River Basin during the two time period of 1960–1990 and 1991–2018. During the period under consideration, several years with a relatively hot weather were observed at Maykhura station: 1966, 1970, 1971, 1973, 1977, 1979, 1980, 1987, 1988, 1990. Additionally, in contrast to them, rather cold year weather periods were observed: 1964, 1967, 1969, 1972, 1974, 1975, 1976, 1981, 1982, 1984, 1989. During the period 1990-2018, in several years, relatively hot weather was observed at Maykhura station including 1997, 2002, 2006, 2007, 2008, 2010, 2014, 2015, 2016, and 2017. On the contrary, the cold weather periods were observed for the following years: 1991, 1992, 1993, 1995, 1996, 1998, 2004, 2005, 2009 and 2012. Analyzing the temperature values over the years (1960-1990) at Hushyori station, we can say that relatively, several years with relatively hot weather were observed during the considered period: 1963, 1966, 1970, 1971, 1973, 1977, 1979, and 1988. Additionally, the opposite of them was observed in rather cold winter periods of weather: 1964, 1969, 1972, 1974, 1982, 1984, and 1989. For the second period (1991-2018), there were few years with  
Figure 3: The mean annual temperature in the upstream, midstream, and downstream regions of the Varzob River Basin in Tajikistan during the two historical periods of 1960-1990 and 1991-2018.  
relatively hot weather: 2001, 2007, and 2016. Additionally, the opposite was observed in rather cold winter weather periods: 1991-1993, 1996, and 2012. Table 2 shows the trend analysis of the average temperature in the upstream, midstream, and downstream areas of the VRB. In the Anzob region (upstream area), according to the observational data in this region, the mean temperature trend in the first period (1961-1990) was recorded in March, September, and November. However, with a relatively large difference in the second period (1991-2018), a considerable increase can be observed in most months of the year. In general, from 1961 to 2018, the average air temperature in January, May, September, October, and December recorded a significant trend. The mean temperature in the Maykhura region in the period from 1964 to 1990 in January and September revealed a significant trend. However, in the next 30 years, that is, from 1991 to 2017, the average air temperature in almost all months, except for August, November, December, and January, has shown a significant trend. In general, during the period from 1964 to 2017, in January, February, March, April, May, and September, an increasing trend in mean temperature was observed. The air temperature in the period from 1960 to 1990 at Hushyori station (downstream region) in January, April, May, September, November, and December shows an upward trend. In February, March, June, July, August, and October, a downward trend was registered (Table 2). In total, six different months of the year have an upward trend at Hushyori station, and the other 6 months of the year, on the contrary, have a downward trend. During the period 1991-2018, in January, March, April, May, June, and July, a significant increase in air temperature was shown. During the same period, only in November and December, the air temperature recorded a downward trend.