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УДК: 627.133 (575.144)
Khikmatov F.Kh., DSc.
professor land hydrology department National University of Uzbekistan named after Mirzo Ulugbek
Uzbekistan, Tashkent Ziyaev R.R. associate professor land hydrology department National University of Uzbekistan named after Mirzo Ulugbek
Uzbekistan, Tashkent
STATISTICAL ASSESSMENT OF THE ROLE OF CLIMATE FACTORS IN THE FORMATION OF RUNOFF ZERAVSHAN RIVER
Annotation: the article defines the elements of the flood of the river. Zeravshan for two calculation stages. A statistical assessment of the relationship between the volume of floods and climatic factors - precipitation and air temperature was made. The resulting regression equations are recommended to be used in hydrological calculations and to determine the volume of river flow during the filling period.
Keywords: river, river basin, flood period, water flow, water volume, climatic factors, precipitation, air temperature, static relationships, regression equations, accuracy of equations.
Introduction. According to UN data, more than 20 liters of water are needed for normal human activities in one night, and another 50 liters are needed for the use of sanitary systems. Currently, 1.1 billion people in the world use only about 5 liters of water a day. In European countries, people use 200 liters of water a day, and in the United States, 400 liters. By 2025, about 3 billion people around the world will suffer from a lack of water. Today, 261 river basins in the world contain territories of two or more countries. Such areas cover 45.3% of the earth's surface. 40% of the world's population lives in these areas [3].
Nowadays, as a result of the global climate change, the scarcity of water resources is felt more strongly every year on our planet, especially in its arid regions. Since the second half of the last 20th century, on a global scale, as a result of climate change, more precisely, warming, the air temperature is increasing, which is causing a decrease in atmospheric precipitation. This process applies to the Central Asian region, including the Zarafshan river basin. Due to this, it is necessary to conduct serious hydrometeorological studies to determine the consequences of the increase in air temperature in the river basin and draw appropriate practical conclusions from it [8, 9, 11].
In the mountain rivers of Central Asia, including the Zarafshan River, 8085 percent of the annual flow flows during the flood season. The period of flooding in the river starts from the end of April, the beginning of May and lasts until October. The study of the connection of the volume of the flow during the filling period with atmospheric precipitation and air temperature is one of the actual hydrological issues related to the effective organization of the use of water resources of the Zarafshan River.
The issues of the formation of river flows and their quantitative assessment depending on climatic factors have been considered in the researches of many scientists. In particular, studies aimed at studying this problem were carried out by V.L.Shults, O.P.Sheglova, L.N.Babushkin, V.A.Bugaev, A.M.Ovchinnikov, N.K.Lukina. Currently, researches in this direction V. E.Chub, E.I.Chembarisov, B.K.Tsarev, F.H.Hikmatov, Z.S.Sirlibaeva, L.M.Karandaeva, D.Yu.Yusupova, B.D.Salimova, D.P.Aytbaev, G'.Kh.Yunusov and others are continuing their research. In these researches, the main attention is focused on researching the characteristics of river flow formation in Uzbekistan and adjacent regions.
In the above-mentioned studies, the influence of atmospheric precipitation and air temperature on the formation of the Zarafshan River flood season flow was not considered as a separate research object. More specifically, the annual and interannual changes of the total volume of the Zarafshan River flood season, as well as the conditions of its formation in relation to climatic factors, including air temperature and atmospheric precipitation, have not been thoroughly studied.
The main goal of this research work is focused on statistical assessment of the effects of climatic factors - atmospheric precipitation and air temperature on the formation of the Zarafshan river flow.
In order to achieve the goal of the work, we used the standard data on water consumption observed at the Dupuli hydrological station of the Zarafshan River and atmospheric precipitation and air temperatures recorded at the Dekhauz meteorological station located in the river basin. These data were first processed and summarized and divided into two periods, namely the first base period (1931-1960) and the second base period (1961-1990).
Main results and their discussion. In order to determine the elements of the recharge cycle of the Zarafshan River, flow hydrographs were drawn for two periods based on the daily water consumption data recorded in the river [1, 10]. Using these hydrographs, basic elements such as the beginning and end of the flood period, the total duration time, the flow volume during the flood period and its share in relation to the annual flow volume were determined (Table 1).
It is known that the beginning of the filling period in rivers and its total duration depend on the location of the river basin, its natural-geographical and climatic-meteorological conditions of the area. If the amount of atmospheric precipitation in the studied year is more than the average long-term norm, then the amount of water in the river will be more [4, 5, 6].
The Zarafshan River belongs to the type of rivers fed by snow-glacial waters [5, 6]. That is why the role of waters formed from the melting of eternal snow and glaciers is important in its saturation. In the Zarafshan river, the period of replenishment usually begins at the end of April. The maximum water consumption in the river is observed in the end of July and the beginning of August in the years of high water, and in the years of low water, the maximum water consumption is observed earlier, in June and July.
Table 1. The main elements of the Zarafshan river (Dupuli hydrological station) of the flood period flow
Years of observation Time to continue, day Qt. medium, m3/s 3 3m 40 0 1 Year-on-year, % Years of observation Time to continue, day Qt. medium, m3/s 3 3m 40 0 1 Year-on-year, %
1931 153 265,9 3514,9 78,5 1961 159 283,5 3894,6 82,3
1932 153 303 4005,4 81,4 1962 127 268 2940,7 75,2
1933 153 297,2 3928,7 83,0 1963 151 277 3613,9 80,7
1934 153 288,7 3816,4 81,8 1964 141 351 4276 81,0
1935 153 262,4 3468,7 79,7 1965 140 263,3 3184,9 76,8
1936 150 299,6 3882,8 82,1 1966 148 317 4053,5 80,5
1937 153 279,5 3694,8 82,8 1967 125 281,6 3041,3 73,6
1938 150 255,6 3312,6 78,4 1968 146 353,2 4455,4 81,3
1939 162 266,1 3724,5 84 1969 153 348,3 4604,2 80
1940 129 315,5 3516,4 78,1 1970 174 344,8 5183,6 85,2
1941 169 373,6 5455,2 85,8 1971 155 308,3 4128,8 80,5
1942 161 383,9 5340,2 84,9 1972 141 268,6 3272,2 76,6
1943 131 292,2 3307,2 73,2 1973 160 400,3 5533,7 86,6
1944 155 273,6 3664 81,4 1974 133 266,6 3063,6 77,1
1945 155 303,5 4064,5 83,2 1975 124 294,5 3155,2 75,8
1946 178 260,4 4004,7 84,5 1976 141 301,4 3671,8 78,4
1947 141 284,2 3462,2 80 1977 139 326 3915,1 79,6
1948 157 302,7 4106 82,9 1978 161 334,7 4655,8 82,8
1949 151 339,5 4429,3 81,9 1979 179 302,4 4676,8 83,2
1950 137 329,9 3904,9 79,7 1980 152 288,7 3791,4 80,7
1951 138 241,7 2881,3 74,9 1981 156 292,7 3945,1 81,5
1952 167 342,5 4941,9 85,2 1982 141 220,3 2683,7 72,9
1953 157 316,6 4294,6 83,4 1983 155 311,7 4174,3 82,6
1954 169 304 4438,9 83,1 1984 124 374,3 4010,1 78,3
1955 152 292,4 3840 80,1 1985 141 293,7 3578 78,5
1956 154 327,4 4356,3 83,1 1986 128 261,8 2895,3 75,4
1957 134 234 2709,2 76,3 1987 154 314,5 4184,6 81,4
1958 173 311,8 4660,5 85,5 1988 168 334,5 4855,3 84,2
1959 177 329,1 5032,9 86,2 1989 127 262,1 2876 73,0
1960 143 319,5 3947,5 81,1 1990 160 328 4534,3 83,4
Average 154 299,9 3990,2 81,5 Average 147 305,8 3895,0 79,6
For the two base calculation periods under study, based on flow hydrographs, the total duration of the filling period in the river and the volumes of flows during this period were determined. For example, in the first accounting period (1931-1960), the largest flow volume during the filling period was equal to 5455^106 m3, which corresponded to 1941. For this interval, the smallest flow volume (2709^106 m3) during the filling period was observed in 1957. So, 1957 was a year of low water in the river.
The second accounting period, i.e., during the period of 1961-1990, the largest amount of flow (5533.7^106 m3) was recorded in 1973. In this year, about 87% of the annual flow from the river flowed during the flood season. This value is the largest indicator for both accounting periods (Table 1).
At the next stage of the work, the relationship between the volume of the Zarafshan River flood season and the annual atmospheric precipitation was studied (Fig. 1). Calculations were performed using standard computer programs. Regression equations representing the relationship between the flow volume of the Zarafshan river and climatic factors were created and their accuracy was evaluated (Table 2).
Taking into account the above, the relationship between the size of the flood flow observed in the river and the annual atmospheric precipitation in the basin was studied. For this purpose, the results of statistical evaluations of the relationship between the flow volume of the flood season and the annual atmospheric precipitation were analyzed (Figure 1).
a)
b)
Wt, 106 m3
6000 5500 5000 4500 4000 3500 3000 2500 2000
Wt = 8,7979x + 1520,1 R2 = 0,6223
150 200 250 300 350 400 450 Xy, mm
Wt, 106 m3
6000 5500 5000 4500 4000 3500 3000 2500 2000
Wt = 7,9707x + 1474,3 R2 = 0,4179
150 200 250 300 350 400 450 500 Xy mm
Figure 1. Zarafshan River with the flow volume of the flood period Connections between atmospheric precipitation: a) the first accounting period, 1931-1960 years; b) the second accounting period, 1961-1990.
Regression equations representing the above associations were constructed and their accuracy was assessed (Table 2).
As mentioned above, the Zarafshan River belongs to the type of rivers fed by snow-glacial waters [5, 6]. As a result of the gradual rise in air temperature in the river basin from early spring, first, the snow cover accumulated in the basin during autumn and winter, and then the glaciers formed from them, begin to melt. The highest air temperature in the river basin is mainly observed in the second and third decades of July. This leads to an increase in the water content of the river.
Taking these circumstances into account, in the next stage of the work, the relationship between the volume of the flow during the filling period and the average annual air temperatures was studied. For this purpose, graphs of the relationship between the volume of flow during the recharge period and the average annual air temperature were drawn for two calculation periods (Figure 1.). Regression equations were also constructed for these graphs and their accuracy was assessed (Table 2).
b)
Wt, 106 m3
6000 5500 5000 4500 4000 3500 3000 2500 2000
Wt = 575,18t + 1552,4 R2 = 0,4414
Wt, 106 m3
6000 5500 5000 4500 4000 3500 3000 2500 2000
Wt = 1048,8t -628,81 R2 = 0,6786
2.5
3.5
4.5
2.0 3.0 4.0 5.0 6.0 7.0 8.0 ty> °c
Figure 2. Relationships between Zarafshan River flood volume and average annual air temperatures: a) the first accounting period, 1934-1960 years; b) the second accounting period, 1961-1990.
5.5 ty, 0C
We will analyze the accuracy of graphs (Figures 1 and 2) and their regression equations representing the above two types of connections. The results of the calculations are presented in Table 2.
Table 2. Regression equations representing the relationships between flow volume and atmospheric precipitation and air temperature during the flood period and their accuracy
Periods The regression equation Correlation coefficient and its error ro ± aro
Relationship with atmospheric precipitation
First accounting period Wt = 8,7979x + 1520,1 0,79 ± 0,049
Second accounting period Wt = 7,9707x + 1474,3 0,65 ± 0,071
Correlation with air temperature
First accounting period Wt = 575,18t + 1552,4 0,66 ± 0,073
Second accounting period Wt = 1048,8t - 628,81 0,82 ± 0,039
As can be seen from the table data, the value of the correlation coefficients representing the relationship between the volume of flow that flowed from the river during the filling period and the annual atmospheric precipitation is equal to 0.79 for the first calculation period and 0.65 for the second calculation period. We can conclude from this that in the period of the first calculation, the influence of the atmospheric precipitation in the basin on the formation of the volume of the river during the filling period was great.
As can be seen from the second type of connections, the pair correlation coefficient for the first calculation period, which represents the density of the connection between the volume of flow during the filling period and the average annual air temperature, was r = 0.66, and its error was a = ± 0.073.
The value of the correlation coefficient obtained for the second calculation period was r = 0.82, and its error was equal to a = ± 0.039. It can be concluded that the process of melting of glaciers in the Zarafshan basin is accelerating due to the effect of air temperature on the global and, accordingly, regional scale.
It is recommended to use the regression equations obtained as a result of the statistical evaluation of the connections between the volume of the Zarafshon River flood season and climatic factors in hydrological calculations and to determine the volume of the river's flood season flow.
Summarizing the results obtained in the study, the following can be noted as a conclusion:
1. The elements of the Zarafshon River flood period were divided into two basic periods. The highest value of the volume of flow during the filling period determined for both periods was 5533.7^106 m3 in 1973. In this year, about 87% of the annual flow from the river flowed in this period;
2. The relationship between the flow volume of the Zarafshan river and the annual atmospheric precipitation was studied. Regression equations of these relationships were constructed and their accuracy was assessed. The values of the pair correlation coefficients representing the relationship between the flow volume and annual atmospheric precipitation during the filling period of the Zarafshan River were equal to 0.79 for the first calculation period and 0.65 for the second calculation period. These results show that the contribution of atmospheric precipitation was significant in the formation of the Zarafshan River floodplain flow during the first accounting period;
3. The graphs of the relationship between Zarafshan river flow volume and average annual air temperatures were analyzed. The values of the pairwise correlation coefficients representing these relationships were equal to 0.66 in the
first calculation period and 0.82 in the second calculation period. This result indicates that the process of melting of glaciers in the basin has accelerated due to a certain increase in air temperature in the last 30 years;
4. It is recommended to use the regression equations representing both types of connections in the implementation of relevant hydrological calculations, including in the estimation of the flow volume of the Zarafshan River during the flood period.
References:
1. Ziyaev R.R., Erlapasov N.B. Variations of the Zarafshon River's flood flow in characteristic years / Proceedings of the republican scientific-practical conference on regional problems of geography. -Jizzakh, 2017. -P. 152-153.
2. Rasulov A.R., Khikmatov F. H., Aytbaev. D.P. Basics of hydrology. -Tashkent: University, 2003. -327 p.
3. Water is the source of life. insonvaganun.uz
4. Chubb V.E. Izmenenie klimata i ego influence na hydrometeorological processes, agroclimaticheskie i vodnye resursy Republic of Uzbekistan.-Tashkent: "VORIS PUSHRIYOT" LLC, 2007. -133 p.
5. Schultz V.L. Reki Sredney Azii.L.: Hydrometeoizdat, 1965. 692 p.
6. Shcheglova O.P. Pitanie rek Sredney Azii, - Tashkent: Izd-vo SaGU, 1960. -243p.
7. Krupneyshie ledniki Sredney Azii: ledniki Fedchenko i Zeravshansky // Pod ed. LK Davydova. L.: LGU, 1967. 263 p.
8. Yunusov G'.Kh., Haitova N. Study of the hydrological regime of rivers based on new hydrometeorological data // Proceedings of the scientific conference. Tashkent: University, 2004. P. 211 213.
9. Haydarov S.A. Assessment of the influence of climatic factors on the flow of the Zarafshan River // News of the Geographical Society of Uzbekistan. Volume 37. -Tashkent, 2011. -P. 148-151.
10. Hikmatov F.H., Haydarov S.A., Erlapasov N.B. About the annual fluctuations of the Zarafshan river flow and the influence of meteorological factors on it // Information of the Geographical Society of Uzbekistan. Volume 44. -Tashkent, 2014. -P. 85-89.
11. Hikmatov F.H., Ziyaev R.R., Haydarov S.A. About the formation of the Zarafshan River floodplain flow and its shifts // News of the Geographical Society of Uzbekistan, volume 45. -Tashkent: 2015. -P 186-189.
12. Hikmatov F.H.,..., Ziyaev R.R. and others. Hydrometeorological conditions and water resources of the Zarafshan river basin. Monograph. - Tashkent: "Science and technology", 2016. -276 p.
13. Hikmatov F.H., Haydarov S.A. Influence of air temperature on the formation of Zarafshan river flow. -Tashkent, 2012 // News of UzMU. - No. 3. -P. 75-82.
14. Water resources, problems of Arala and surrounding environment. Tashkent: University, 2000. 398 p.
