Abstract
The intensity of agricultural activities and the characteristics of water consumption affect the hydrological processes of inland river basins in Central Asia. The crop water requirements and water productivity are different between the Amu Darya and Syr Darya river basins due to the different water resource development and utilization policies of Uzbekistan and Kazakhstan, which have resulted in more severe agricultural water consumption of the Amu Darya delta than the Syr Darya delta, and the differences in the surface runoff are injected into the Aral Sea. To reveal the difference in water resource dissipation, water productivity, and its influencing factors between the two basins, this study selected the irrigation areas of Amu Darya delta (IAAD) and Syr Darya delta (IASD) as typical examples; the actual evapotranspiration (ETa) was retrieved by using the modified surface energy balance algorithm for land model (SEBAL) based on high spatial resolution Landsat images from 2000 to 2020. Land use and cover change (LUCC) and streamflow data were obtained to analyze the reasons for the spatio-temporal heterogeneity of regional ETa. The water productivity of typical crops in two irrigation areas was compared and combined with statistical data. The results indicate that: (1) the ETa simulated by the SEBAL model matched the crop evapotranspiration (ETc) calculated by the Penman–Monteith method and ground-measured data well, with all the correlation coefficients higher than 0.7. (2) In IAAD, the average ETa was 1150 mm, and the ETa had shown a decreasing trend; for the IASD, the average ETa was 800 mm. The ETa showed an increasing trend with low stability due to a large amount of developable cultivated land. The change of cultivated land dominated the spatio-temporal characteristics of ETa in the two irrigation areas (3). Combined with high spatial resolution ETa inversion results, the water productivity of cotton and rice in IAAD was significantly lower than in IASD, and wheat was not significantly different, but all were far lower than the international average. This study can provide useful information for agricultural water management in the Aral Sea region.
Highlights
The objectives of this study are as follows: (1) with the South Aral Sea shrinking faster than the North Aral Sea, we aim to explore the difference between the water consumption of crops in the rump irrigation areas of the South and North Aral Seas (Nukus and Syr irrigation area) and find the reasons for this difference; (2) to reveal the difference in water productivity between the Amu Darya irrigation area (IAAD) and the Syr irrigation area (IASD) and put forward constructive suggestions
At the KZL meteorological station, the evapotranspiration simulated by SEBAL (ETsebal) is well-matched with the ETobserved with an R2 value of 0.86, an RMSE value of 0.85 and a percent bias of 12% (Figure 3a)
The results show that the average annual ETa of the irrigation of the Amu Darya delta (IAAD) was 1138 mm, whereas that of the irrigation of Syr Darya delta (IASD) was 687 mm
Summary
Since 1960, the excessive utilization of the water resources of the Amu Darya and Syr. Darya river basins has significantly reduced the amount of water inflow to the Aral Sea, Remote Sens. Studies have shown that agricultural intensification in the Amu Darya and Syr Darya river basins is the main cause of the crisis of the Aral Sea [3,4,5]. The increased demand for irrigation water has resulted in a significant reduction in inflow into the Aral Sea [2,6]. The level of the southern Aral Sea fed by the Amu Darya River has fallen sharply due to a significant reduction in the inflow, while the level of the northern Aral Sea, obtaining water from the Syr Darya river, has been increased with an increased inflow from 1987 to
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