## 4 Results
### Precipitation Analysis in the Varzob River Basin
The average annual relative humidity is 54% and the average monthly readings range from 38% to 67%. We can note that March is considered the most intense month in terms of precipitation, and August is considered the driest. Considering the second period (1991-2018), it can be said that the period of precipitation has partially changed in the time of precipitation, so in February, there was an increase in precipitation and a decrease in April. The driest month was August. Figure 4: The mean annual temperature change points during the (**a**,**d**,**g**) 1960–1990, (**b**,**e**,**h**) 1991–2018, and (**c**,**f**,**i**) 1960–2018 periods based on the Pettitr’s test at Anzob, Maykhura, and Hushyori meteorological stations in the upstream, midstream, and downstream regions of the Varzob River Basin in Tajikistan. Considering the period 1960-1990 at Anzob station, one can note that the years with the maximum amount of precipitation were 1963 and 1969, and the year with the least amount of precipitation was 1971. Relative to the obtained graph, it is possible to single out the cyclicity of the repetition of years with unstable precipitation. During the second period 1991-2018, the years with the maximum amount of precipitation were: 1991, 1993, 2004, 2006, 2009, and 2011, while the minimum amount was recorded in the following years: 1996, 2000, 2001, 2002, 2003, 2008, 2010, and 2012-2016 (Figure 6). Figure 5: The monthly precipitation in the upstream, midstream, and downstream regions in the Varzob River Basin during the two time periods of 1960–1990 and 1991–2018. Analyzing the period of 1964-1990 at Maykhura station in the midstream region of the Varzob River Basin, one can note the years with the maximum amount of precipitation--1964 and 1969--as well as the years with the minimum amount of precipitation--1971. During the second period 1991-2018, the years with the maximum amount of precipitation can be noted--1991, 1993, 1998, 2002-2004, 2009, and 2012--as can those with a minimum amount of precipitation--1995, 1996, 2000, 2001, 2008, 2010, and 2015 (Figure 6). With regard to the obtained graph, one can single out the cyclicity of the repetition of years with unstable precipitation, i.e., sharp fluctuations in precipitation, with strong bursts of years with high precipitation and as opposed to those with the least precipitation. The repetition of years with unstable precipitation, i.e., below normal, ultimately affects the overall flow of the river. Figure 6: The annual precipitation 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. During the period 1960-1990 at Hushyori station, the years with the maximum amount of precipitation were noted to be 1964 and 1969, whilst the year with the minimum amount of precipitation was 1971. During the second period 1990-2018, the years with the maximum amount of precipitation were noted to be 1991, 1993, 1998, 2002-2004, 2009, 2006, and 2013, and the years with the minimum amount of precipitation were 1992, 1995, 1996, 2000, 2001, 2008, 2012, and 2017. Concerning the obtained graph, one can single out the cyclicity of the repetition of years with unstable precipitation, i.e., sharp fluctuations in precipitation, when there were strong bursts of years with high precipitation as opposed to those with the least precipitation. Table 4 shows the seasonal trend in precipitation in the upstream, midstream, and downstream areas of the VRB. During the period from 1960 to 1990, a significantly increasing precipitation was recorded in the Anzob region only in December and January. During the period from 1991 to 2018, a decreasing trend was recorded in June, July, and December. In general, during the period from 1960 to 2018, a significantly increasing trend was indicated in January and February, and a significantly downward in precipitation was shown in April and May. In the Maykhura station, during the period from 1964 to 1990, precipitation showed a decreasing trend only in April.