Overloading analysis of irrigation area in basins of Tarim River in different years

Abstract: It is important for policy-making of irrigation to better understand if the irrigation area is overloaded. In this study, we explored the irrigation area overloading problem in basins of Tarim River in China in 2010 and 2020. The study focused mainly on four rivers and one mainstream in the Tarim River. The affordable irrigation area was calculated as the ratio of maximal irrigation amount for agriculture and gross irrigation quota. The available irrigation amount for agriculture was determined by subtracting water for lives, livestock, industry, ecology and discharged water to mainstream from total water amount. The data of irrigation area, gross irrigation quota, irrigation amount for lives, liverstock, and industry in 2010 were collected by investigation and provided by local administration. Those in 2020 were obtained according to an integrated management plan of Tarim river. Water for ecology was from previous studies. The overloading area was defined as the difference of real or planned irrigation area and maximal irrigation area. The results showed that: 1) There was a total of 17.1×105hm2 irrigation area in four source streams and mainstream of Tarim River in 2010, while the maximum area allowed was only 12.9×105 hm2, suggesting an overloaded area of 4.33×105 hm2 that was about 33.6% overloaded; Except for the Hotan-river basin, the others basins such as Yarkant-river, Aksu, Kaidu river-kongque river and the main stream of Tarim River were overloaded by 0.87×105, 1.41×105, 1.65×105 and 0.40×105 hm2, and corresponding to an overloading percentage of 21.0%, 35.2%, 84.6% and 66.7%; 2) In 2010, four basins were overloaded, but only three in 2020; in 2020 the overloading of the four source streams and mainstream of Tarim River decreased 2.98×105 hm2 with the percentage of 68.86% compared with that in 2010; But the overloading was serious in basins of Kaidu river-kongque river and the mainstream of Tarim River with the overloading rate of 31.6% and 34.0%, respectively; 3) There were two main reasons for the increasing of environment capacity in 2020: one was the improvement of the level of water utilization, the irrigation quota in basins of Hortan river, Yarkant river, Aksu river Kaidu river-kongque river and the main stream of Tarim River in 2020 were decreased by 12.4%, 15.8%, 18.0%, 11.6% and 9.9%, respectively compared with that in 2010; the other reason was the reduction of planning irrigation area since the planning irrigation area in basins of Aksu river, Kaidu river-kongque river and the mainstream were reduced by 0.64×105, 1.23×105, and 0.01×105 hm2, respectively. The study can provide data support for irrigation plan of the Tarim river basin.