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Mansurov Safar Rakhmankulovich, assistant, Department of "Hydrology and Hydrogeology" Tashkent Institute of Irrigation and Agricultural Mechanization Engineers
E-mail: [email protected]
DETERMINATION OF THE VOLUME OF FLAKY SEDIMENTS AND OTHER SEDIMENTS DEPOSITED AT THE BOTTOM OF THE SOUTH SURKHAN RESERVOIR
Abstract: The effective utilization of water resources in reservoirs of Uzbekistan is largely depends on rapid siltation of their cup. For this reason, it is important to study sedimentation of water reservoir as Surkhandarya region which with dry climate and based on agricultural irrigation. Efficient utilization of reservoirs and their related scientific and practical conclusions are one of the main issues today.
Keywords: Water reservoir, Efficient use, water, Sediment, Consumption, river, hydrology, volume, streams.
The main purpose of this article is to determine the volume of fuzzy irrigation and other sediments deposited at the bottom of the South Surkhan reservoir. The following tasks have been identified and resolved:
- Consumption of sediments Surxondarya for accounting period between 1964 and 2013, kg/s;
- The amount of sediment (Wsoy) in reservoir, brings by the rivers and streams which provided hydrometric observations;
- Amount of sediments in reservoir that can be added by rivers and streams without hydrometric observations;
- The amount of sediments which added from the surface of the reservoir to and its coastal area.
Methods and analysis. For quantitative assessment of sedimentation balance equation of South Surkhan reservoir was used the data of the standardized hydrological observations, including data of hydrometric and hydrological observations which made at special stations. Calculation of quantitative assessment of elements of sedimentation equation was performed in the following way [9]:
The volume ofsediments which flows to South Surkhon reservoir by Surkhandarya is defined by the following expression:
W = R T-n
river mean
there: Rmean - consumption of average annual sediment flow calculated for the accounting period between 1964-2013 for Surxondarya, kg/s; T - The number of seconds in a year, its equal to 31.54106 seconds, n-is the number of observation years [2].
Average long-term sediment flow rates which brings to Surkhondaryo reservoir for calculation period (1964-2013) calculated using the above expression:
I Rdi
6596 = 131.9 ^,
50 s
Knowing the value of the average long-term sedimentation (R, ) and value of T, calculated volume of the sedi-
v d.meany '
ment streams to Surkhandarya's South Surkhon reservoir was determined with the help of above expression:
W„ = 131.9 kg • 31.54-106 c • 50 =
H s
= 208006.3 • 106 kg = 208 • 106 ton The amount of sediment streams (Ws) which brings by rivers and streams that have hydrometric observations was also calculated by the expression:
kg
Ws =X Rs.n
■T • n = 28.4 — • 31.54 • s
•106 s • 50 = 44.78-106 ton.
For calculation the amount of sediments flows that can be added from streams without hydrometric observations to the water reservoir provided with using a soil cleaning map which created by O. P. Sheglova. As observed, there are more than 10 smaller streams which adds to South Surkhon reservoir, with the F = 1500 km2 water collecting area. In the basin of the river and river basin's which provides hydro-meteorological observations, claning module is equal to 538 tonnes/km2 [3; 4; 5]. The following steps were done to calculate this amount. The total area of the river and streams which provided hydromet-ric observations is equal to 10053 km2. Observed that their average annual sediment stream (WR) was 5055.6 tonnes. Using this information, claneaning module of river and streams which provided hydrometric observations was calculated as follows [2; 6; 11].
5712.9ton __ ton
MR = ^ R F
10625km2
- = 538-
km2
year
When used map of soil washing by O. P. Sheglova, it was found out that the Soil Surface Washing Module was equal to 750 ton/km2 in South Surkhan reservoir bassin (Figure 1).
DETERMINATION OF THE VOLUME OF FLAKY SEDIMENTS AND OTHER SEDIMENTS DEPOSITED AT THE BOTTOM OF THE SOUTH SURKHAN RESERVOIR
Figure 1 Soil drainage map, t/km2 year (southern part of Central Asia, O. P. Sheglova) [1]
1 - < 50.2-50-100, a -100-200.4-200-500.5-5001000.6-1000-2000.7-2000-5000.8 - >5000
Using this value above, calculated the flow of sediments in the basin of streams which not provided hydrometric observation as follows:
j _ ^^chuckma
318.3 -106 ton 6 ton
_ 6.36-10 —
50 yy
yy
After that, the amount of sediment flows which comes from not provides hydrometric observations was determined as follows.
WXO = RXO•T • n = 35.66 ^ • 31.54 • . . s
•106 s • 50 = 56.23 • 106 ton
The results of the above calculations are given in the table.
Table 1.- Calculation of the amount of sediments which incomes from streams which not carried out hyrometric observations
Amoun t of streams Area of collection basin km2 Average washing module, MR, t/km2 year R kg S WX O c = R -T ■ n, 106
10 1500 750 35.66 56.23
The calculation of the amount of sediment flow (Wqb) which adds from the surface of the reservoir and along the coastal area of the reservoir provided as:
Wt=F - (F + F + F ) = 11800-10053-1500 = 247 km2.
qb wr K d s h.oy
There: Fwr- is a water collecting area of reservoir, equal to 11800 km2; Fd and Fs - water collecting area of of rivers and streams which provides hydrometric observations, equal to 10053 km2; Fh - water collecting area of of rivers and streams which not provides hydrometric observations, it equal to 1.500 km2.
As washing module equal to 750 ton/km2, the amount of sediments which adds from the coastal zone and surface stream of the reservoir is calculates as follows:
Wqb = Fqb ■ MR ■ n = 247 kg2 ■ 750 ton/km2 ■ 50 = 9.3 ■ 106 ton.
Using the results of the above calculations, the sediments resulting from the sinking of the muddy outlets in the reservoir during the exploitation period were as follows:
a) Determination of the amount of deposition (W_) generated by the sedimentation of rivers and rocks in the reservoir in the unit of weight measurement:
W = Wd + Ws + Who + Wqb= (208 + 44,78 + 56,23 + 9,3) ■ 106 = 318.3 ■ 106 ton° q
b) Determination of the amount of sediments in reservoir in volume measurement;
n =
Ws = 318.3-1061 yR 1.15t/m3
= 276.8
•106 m3,
According to the batimetry, the cumulative weight of the precipitated sediments in the South Surkhon reservoir in 1979 has changed with following interval: the maximum value is 1.74 t/m3, the minimal value is 1.09 t/m3, and the average value of the specific weight of the sediments was taken as 15 t/m3 [2; 8].
Table 2.- Quantitative values of the bottom sediments of South Surkhon reservoir
Quantity W r W h.o. q.b. W ss
106 ton 208 44.78 56.23 9.3 318.3
106 m3 180.86 38.94 48.89 8.08 276.8
% 65.35 14.07 17.66 2.92 100
Conclusion
The results of the calculations show that during the exploitation period, the South Surkhan water reservoir flows 318.3 mill. tons or 276.8 million m3 of sediments. Thus, the water value of the Southern Surkhan reservoir has been reduced to such a size.
Assessment of the intensity of overflowing of the South Surkhon reservoir with sediments in the weighing unit is:
Ig =
318.3 -106ton 6 ton
= 6.36 -10 —
n 50 yy yy
6) Assessment of the intensity of overflowing of the South Surkhon reservoir with sediments in the volume units:
Wl
n
Ig = — =
276.8
•106 m3
= 5.5 •lO6
m
50 year year
Summary:
1. The average annual (1964-2013) sedimentation of the Surkhandarya water reservoir is equal to 208 • 106 tons.
2. The amount of sediment flow from rivers and streams which provides hydrometric observations is equal to 44.78 • • 106 tons.
3. The amount of sediment flow from rivers and streams which not provides hydrometric observations is equal to 56.23 • 106 tons.
4. The volume of sediments added to the reservoir by the surface stream and its coastal area is equal to 9.3 x 106 tons.
During the calculation period the volume of bottom sediments into the reservoir was 276.8 million. m3. Given the fact that the water of river and streams have been blocked since 1962, it is clear that 53 years have passed since the sediments began to flood. The average annual amount of bottom sediments in the calculation period is 5.5 mill. m3. Until now, the amount of sediment falling to the reservoir was 291.5 mill. m3. This indicator is 36.4% with compearing with projected water volume.
In general, the results of the calculations show that the water reservoir capacity of the Southern Surkhan reservoir is 508.5 mill. m3.
References:
1.
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