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УДК 627.133
Yunusov G.Kh., Doctor of Geographical Sciences Head of the Department "Terrestrial hydrology" National University of Uzbekistan named after Mirzo Ulugbek
Uzbekistan, Tashkent Sharipova G.R. graduate student Department of Land Hydrology Faculty of Hydrometeorology, National University Uzbekistan named after Mirzo Ulugbek Uzbekistan, Tashkent
HYDROLOGICAL REGIME OF THE RIVERS OF THE
KASHKADARYA BASIN AND ASSESSMENT OF LOCAL WATER
RESOURCES
Abstract: The article is devoted to the assessment of the hydrological regime of the rivers of the Kashkadarya basin and the local water resources of the oasis. In it, at first, the intra-annual distribution of river runoff by months of the basin and the coefficient of river nutrition were calculated. In the following parts of the work, the coefficients of variability of the river runoff of the basin and changes in water resources for two calculation periods were determined. At the end of the study, the main indicators of river runoff in the Kashkadarya basin were calculated. All calculations are performed for different accounting periods. The results obtained during the study were compared and analyzed with data from previous studies, and scientific conclusions were given.
Keywords: river, water discharge, runoff module, runoff layer, runoff volume, hydrological regime, runoff change during the year, coefficient of variation, water resources.
The hydrological regime of the rivers of Central Asia was studied in the middle of the last century by V.L.Shultz, O.P.Shcheglova, M.N.Bolshakov and others [1, 3, 4, 5]. In the future, similar studies were continued by G.N.Trofimov, V.E.Chub, Yu.N.Ivanov, A.A.Rasulov, F.H.Hikmatov and others [2, 6-8, 9]. The results of these studies have been used in the relevant fields of hydrological and water management calculations.
By now, over the next 40 years, a sufficiently large amount of material has been accumulated, which allowed V.E. Chub to clarify previously defined characteristics of the flow of the rivers of the Kashakadarya basin. The results of a special study by V.E. Chub [3] made it possible to make a more detailed assessment of the local water resources of the Kashkadarya oasis, which differ in the completeness of the coverage of the hydrological material and, accordingly, their reliability. This assessment is necessary taking into account
the longer series of observations and its implementation has become a time requirement. The results of such studies are necessary for solving problems related to the sustainable development of the country and its individual regions, such as the Kashkadarya Oasis.
In the last century, hydrological observations with different series of durations were conducted at 50 hydrological sites in the Kashkadarya River basin. Taking this into account, in this work we have selected hydrological posts with longer series of actual observations.
When using water resources for the purposes of irrigated agriculture, data on the intra-annual distribution of river flow are of particular importance. As is known by V. L. Shultz, the annual distribution of river runoff can be very significantly influenced by the thickness of the snow cover, which determines the position of the snow line, and the height of the glaciers. These hydrological indicators are also typical for the Kashkadarya basin. In this regard, we have calculated the annual distribution of the flow of the studied rivers using data from recent years of observations. The calculation results are shown in Table 1.
In the table we can see, that rivers of the Kashkadarya basin differ in a certain range of the time of the onset of the monthly maximum and by a different anual flow distribution. In the table we can see, that rivers of the Kashkadarya basin have been differ in a certain range of the time onset of the monthly maximum and by a different anual flow distribution. For example, at average catchment heights up to 2000 m (Kashkadarya - Varganza, Jinydarya -Jazz), the monthly maximum flow (20% or more of the annual) is observed in April. On the rivers Akdarya (Khazarnau), Tankhizydarya (Katagan), Yakkabagdarya (Tatar), the average height of catchments ranges from 2200 -2750 m, the monthly maximum flow is observed in May and even in June.
Table 1
Intra-annual distribution of river runoff by months (in %) and values of the
Schulz coefficient (5)
River - post Billing Months 5
period I II III IV V VI VII VIII IX X XI XII
Kashqadarya I 1933-1952 5,0 8,2 16,2 23,8 16,6 8,0 4,6 3,7 3,2 3,3 3,5 4,2 0,18
- Varganza II 1927-2020 3.3 5.1 10.6 15.5 10.4 4.6 2.6 1.93 1.7 1.8 2.2 3.1 0,15
Djinydarya- I 1933-1952 4,6 12,3 7,9 20,0 18,3 7,6 4,9 4,3 4,7 5,2 5,3 5,0 0,26
Jauz II 1941-2020 0,9 1,1 1,9 3,1 2,7 1,5 1,0 0,9 0,9 1,0 1,1 1,1 0,31
Akdarya- I 1933-1952 2.6 2.9 4.5 8.6 13.9 21.7 19.0 10.8 6.3 4.0 3.2 2.9 0,74
Khazarnau II 1927-2020 2.6 2.7 5.6 11.2 17.4 28.4 30.6 21.5 10.6 6.2 4.8 3.4 1,0
Tankhizidarya- I 1933-1952 2,0 2,2 3,5 9,6 22,8 28,0 15,9 5,9 3,3 2,5 2,2 2,2 0,39
Kattagan II 1951-2020 0.9 1.0 2.1 5.8 11.9 13.2 6.3 2.0 1.0 0.8 1.0 1.0 0,29
Yakkabagdarya-Tatar I 1933-1952 1,8 1,3 2,7 9,0 22,7 28,0 17,3 6,5 3,5 2,70 2,40 2,19 0,44
II 1930-2020 1.2 1.9 1.9 6.7 15.8 20.2 11.8 4.5 2.5 1.8 1.6 1.4 0,42
Notes: 1 - according to V.L. Sc
iulz, 2 - results obtained
by the authors.
This is evidenced by the graphs constructed on the basis of the data in Table 1, the average annual distribution of the runoff of characteristic rivers of the studied area (Figs.1 and 2). The results of calculations of the annual distribution of the flow of the rivers of the Kashkadarya basin were compared with the data of V.L.Schultz (Table 1).
Fig. 1. Average long-term intra-annual distribution of runoff by month (% of annual), p.Kashkadarya - K.Varganza
w,%
25
20 15 10 5 0
■ according to Schultz ■ according lo the authors
|| ||
1.1, II II II II
1 2 3
10 11 12
4 5 6 7 8 months
Fig.2. Average long-term intra-annual distribution of runoff by month (% of annual), p.Akdarya - K.Hazarnau
This paper presents an assessment of the indicators of runoff and the share of river power sources based on the materials of 5 hydrological posts with sufficiently long series of observations. For this purpose, the values of the coefficient 5 were calculated and, based on them, the power sources of the rivers were clarified.The results are compared with the data of V.L.Schultz (Table 1).
The values of the parameter 5 calculated by us with the involvement of materials from recent years of observations, are close with the given values (5) of V.L. Schultz. However, it should be noted that in recent years, for most of the rivers in the Kashkadarya river basin, the runoff for the months of March-June is higher than had V.L. Schultz (Table 1).
It is known that V.L.Schultz attributed p.Kashkadarya in the group of snow-fed rivers, and according to our results, this river belongs to the snow-rain type. The rivers Jinydarya, Akdarya, Yakkabagdarya by V.L.Schultz were attributed to the snow-glacial type of source, which is also confirmed by our calculations.
As can be seen from Table 1, the values of 5 decreased for the
Tankhizydarya (Kattagan) and Yakkabagdarya (Tatar) rivers.The reason for this is the intensive melting of glaciers in the high-altitude part of the studied basin and a decrease in their area, as well as the size of eternal snow in the relatively low zones of the basins of these rivers. For example, as mentioned above, the total area of glaciers in the Kashkadarya basin according to V.L.Shultz was 20.3 km2, and subsequently it was decreased by 23.6%.
In this work, the issues of long-term variability of the runoff of the rivers of the Kashkadarya basin are also considered on the basis of the materials of the 10 above-mentioned hydrological stations. We calculated the values of the coefficients of variation for three selected calculation periods (Fig. 3).
In this paper, the issues of long-term variability of the flow of the rivers of the Kashkadarya basin are also considered on the materials of the 10 above-mentioned hydrological posts. We calculated the values of the coefficients of variation for three selected calculation periods (Fig. 3).
Fig.3. Values of the coefficients of variation calculated for the selected periods Note: A - the period covering all the years of observations; B - the period up to 1970; C - the period from 1971 and subsequent years.
As can be seen from Figure 3, for each of the three calculation periods for the rivers of the upper part of the Kashkadarya (Varganza), the values of the coefficients of variation are almost the same, only in the last period (C) it is less relative to the previous calculation periods A and B. For the Tankhizydarya, Guzardarya, Kashkadarya (Chimkurgan) rivers, the coefficient of variation increased slightly in the last calculation period.
It should be noted that on the rivers of the Guzardarya basin, the values of the coefficient of variation of annual runoff fluctuate within significant limits. At the same time, for the Uradarya River, the values of the coefficient of variation in the last period significantly decreased compared to the second
period. In general, for all three selected periods, the values of the coefficients of variation varied in the range of 0.24 - 1.13. If its minimum value falls on Akdarya (Khazarnau), then the maximum value is obtained for Kichik Uradarya River (Gumbulak).
The study of changes in river flow is of great scientific and practical importance for the planned organization of water management of any territory in the future. To this end, the corresponding calculations were performed for the following two periods: I. Conditionally natural period (inclusive up to 1970); II. The period of intensive land development (1971-2018). When allocating these periods, the intensive development of the lands of the Karshi steppe is taken into account. Calculations were made on the basis of materials from 10 hydrological sections (Table 2).
Table 2
Changes in river water runoff for settlement periods (I, II)
№ River - post I II AW, 106 m3 %
Numbe r of years Qmid, m3/c Wy, 106 m Numbe r of years Qmid, m3/c Wy, 106 m3
1 Kashkadarya -Varganza 44 5.43 171.3 50 5,09 160,5 -10,7 -6,7
2 Kashkadarya-Chirakchi 25 24.9 785.3 50 20,1 633,3 -132,9 -21,0
3 Kashkadarya -Chimkurgan 8 16.71 527.0 50 12,71 400,9 -126,2 -31,5
4 Djinydarya-Jauz 29 1.48 46.7 50 1,51 47,6 0,93 1,95
5 Akdarya-Khazarnau 44 12.88 406.2 50 11,62 366,5 -39,6 -10,8
6 Tankhizidarya-Kattagan 20 4.8 151.4 50 3,66 115,3 -36,01 -31,2
7 Yakkabagdarya-Tatar 40 6.63 209.1 50 5,44 171,5 -37,6 -21,9
8 Guzardarya-Pachkamar 6 5.05 159.3 50 5,53 174,6 0,9 0,53
9 Kichikupadarya-Gumbulak 3 3.2 100.9 50 1,41 44,4 -56,8 -127,9
10 Upadarya-Bazartepa 6 3.1 97.8 50 4,08 128,55 23,8 18,54
The average annual values of water flow rates (Qmid) and annual runoff volumes (Wy) of selected rivers for the specified calculation periods are calculated. Then, for the studied rivers of the Kashkadarya basin, the difference in flow volumes (AW) was determined, calculated from the average annual water consumption for each of the two calculation periods. Analysis of the calculated values of the difference in flow volumes showed that in most cases there is a decrease in flow in the second calculation period: its minimum value (AW = 4.0%) corresponds to the Kashkadarya River, and the maximum value is
127.9% at the Kichikuradarya River. The reason for this is the increased water intake above the hydrological levels in the second billing period. Only in a single case (Jinydarya, Guzardarya and Uradarya,) the difference has a positive sign (Table 2). On average, the change in flow for all rivers was -22.81%, which is the result of intensive use of river flow for irrigation purposes.
Based on the available materials on the water flow of the studied rivers, we calculated the following main indicators of river flow: average annual water flow rate (Q, m3/s); flow modulus (M, l/s-km2); flow layer (Y, mm); flow volume - W, million m3 (Table 3).
Table 3
The main indicators of the runoff of the rivers of the Kashkadarya basin, calculated for different calculation periods
River - post A source Billing period F, km2 Q, m3/s M, l/s km2 y, mm W, mln. m3
Kashkadarya -Varganza I 1926-1960 468 5,46 11,7 368 172,2
II 1926-2002 511 5,22 10,2 322 164,5
III 1927-2020 511 5,25 10,4 327 167,2
Djinydarya-Jauz I 1941-1960 163 1,43 4,0 277 45,1
II 1941-1990 152 1,56 10,3 323 49,2
III 1941-2020 152 1,44 10,1 317 48,3
Akdarya-Khazarnau I 1927-1960 845 12,3 14,6 459 387,9
II 1927-2002 845 12,1 14,3 451 381,6
III 1927-2020 845 12,08 14,5 459 387,9
Tankhizidarya-Kattagan I 1926-1960 427 4,30 10,3 318 135,6
II 1951-2002 425 4,11 9,7 305 129,6
III 1951-2020 435 3,92 9,2 291 126,5
Yakkabagdarya-Tatar I 1930-1960 504 6,74 13,4 422 212,6
II 1930-2002 514 6,11 12,1 382 192,6
III 1930-2020 504 5,94 11,8 372 187,3
Guzardarya - Yartepa I 1928-1960 3170 6,0 1,89 60 189,2
II 1928-1965 3170 5,95 1,88 59 187,7
III 1928-1965 3170 5,95 1,88 59 187,7
Guzardarya-Pachkamar I 1928-1964 1260 4,49 3,6 112 141,6
II 1965-2002 1250 4,81 3,8 121 151,7
III 1971-2020 1250 4,00 3,3 103 128,4
Kichikupadarya-Gumbulak I - - - - - -
II 1968-2002 1570 1,29 0,82 26 40,7
III 1968-2020 1570 1,44 0,94 30 47,0
Note: I - according to V.L. Schultz; II - according to V.E. Chub; III according to the authors.
The obtained results of calculations of the main characteristics of the flow of large rivers were compared with the data of V.L. Shultz and V.E. Chub (Table 3). As can be seen from this table, despite the differences in the calculation periods, the values of the average long-term characteristics of the
flow of rivers almost coincide, especially with the results of V.E. Chub. This indicates that over the past 30-40 years there have been no drastic changes in the hydrological regime of the rivers of the Kashkadarya basin.
Thus, we have clarified the values of the main indicators of river runoff: the average annual water consumption, the flow modulus, the layer and the volume of runoff. The obtained results were compared with the data of V.L. Shultz and V.E.Chub. Despite the differences in the calculation periods, the values of the average annual characteristics of river flow do not differ much.
The recorded water resources of the rivers of the Kashkadarya basin are characterized by the following values: the total volume of surface water runoff varies from 600 million m3 to 1.9 billion m3 per year, the total average annual flow rate of rivers is 44.9 m3/s, and the average annual flow volume is 1.416 km3.
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