Impacts of Climate Changes on Spatiotemporal Variation of Cotton Water Requirement and Irrigation in Tarim Basin, Central Asia

Evapotranspiration (<i>ET_c</i>), crop water requirement (<i>D_cr</i>), irrigation (<i>IR</i>) and irrigation leaching amount (<i>IR_lc</i>) play a critical role in optimizing irrigation scheduling and are also important for hydrological cycle processes and ecological environment in arid regions. This research examined the spatiotemporal variability of the <i>ET_c</i>, <i>D_cr</i> and <i>IR</i> of cotton using data from 16 meteorological stations in the Tarim basin (TRB) of arid Northwest China during 1961-2017. The results showed that the mean annual <i>ET_c</i> of cotton exhibited a significant decreasing trend, with a change rate of 12.965 mm·10 a^-1 and 18.357 mm·10 a^-1 during 1961-2017 and 1961-1990, respectively. Subsequently, it experienced a substantial increase with a change rate of 16.833 mm·10 a^-1 after 1990. The <i>D_cr</i> of cotton followed a decreasing trend at a rate of 15.531 mm·10 a^-1 and 21.99 mm·10 a^-1 during 1961-2017 and 1961-1990, respectively. The <i>D_cr</i> of cotton provided an increasing trend at a rate of 20.164 mm·10 a^-1 during 1991-2017. The <i>IR</i> of cotton followed a decreasing trend at a rate of 19.66 mm·10 a^-1 in 1961-2017 and 24.531 mm·10 a^-1 in 1961-1990, but an increasing trend at a rate of 14.437 mm·10 a^-1 in 1991-2017. The <i>IR_lc</i> of cotton decreased by 2.566 mm·10 a^-1 and 3.663 mm·10 a^-1 during 1961-2017 and 1961-1990, respectively. After 1990, it experienced a substantial increase by 3.331 mm·10 a^-1. Wind speed exerted the greatest influence on the variability in <i>D_cr</i> and <i>IR</i> between 1961 and 1990, while shine hour played a more prominent role in explaining the variability in <i>D_cr</i> and precipitation may have played a more significant role in explaining the variability in <i>IR</i>. This study is helpful for the scientific planning for agriculture, water resource allocation and water-saving irrigation in arid regions.