Syrdarya natural flow

During the 75 years the annual volume of the Syrdarya natural flow varied from 18 km in 1975 to 53 km in 1969. The most water abounding was the decade 1951-1960 with a mean volume of 33.9 km, and the most water short decade was 1971-1980 with a mean value of 24.6 km. ... 

Herein is described the natural fluctuatirms of the Amudarya and Syrdarya annual flow, the variatiOTis in the river inflow to the deltas and to the Aral Sea that occurred (and are still in progress) as a result of economic activities in the drainage basins of the abovementioned rivers. This process is a crucial factor leading to the shallowing and division of the Aral Sea into two parts the Large Sea and Small Sea. 

The long-term fluctuations of annual volumes of the natural flow of the Amudarya and Syrdarya rivers (water resources), total inflow to the deltas and to the Aral Sea and main annual water levels of the Large and Small Sea are shown in Fig. 6. 

Table 7 Natural flow of the Amudarya and the Syrdarya in the catchment area...

Fig. 6 Total natural flow of the Amudarya and the Syrdarya rivers, inflow to the deltas and to the Aral Sea, water levels in the Aral Sea 1 natural flow 2 and 3 inflow to the deltas and to the Sea 4 water level in the Large Sea 5 water level in the Small Sea...

According to the data of simultaneous observations in several sites on the Syrdarya, the wasteful (in addition to irrigation consumption) losses of water before the 1960s made up 6 km per year and varied as a function of volume of inflow to V. Kokbulak. During the last decades during which the majority of Syrdarya flow has been diverted to the irrigated lands the natural losses of water decreased considerably. 

The average values (of natural river flow) before and after 1960 coincide practically (101 and 100 km per year), in separate decades of the 75-year period the mean values deviate from the average in the Amudarya by +6% and —12%, in the Syrdarya by 20%, the total water resources of the Aral Sea watershed ... 

Variation of natural water resources forming on the Aral Sea watershed are characterized by moderate variability both during the stable period of the Sea and in the last 45 years. The average volume of the Amudarya annual flow in 1932-1960 and 1961-2006 is equal to 70.3 and 69.4 km per year and Cy = 0.15. The analogous Syrdarya flow is 36.2 and 36.8 km per year with Cy = 0.18 and 0.20. 

---