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Zhao X.,Xinjiang Institute of Ecology and Geography | Xu H.,Xinjiang Institute of Ecology and Geography | Wang M.,Xinjiang Agricultural University | Zhang P.,Xinjiang Institute of Ecology and Geography | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering

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. © 2015, Chinese Society of Agricultural Engineering. All right reserved. Source

Zhang Z.,Tsinghua University | Hu H.,Tsinghua University | Tian F.,Tsinghua University | Yao X.,Xinjiang Tarim River Basin Management Bureau | Sivapalan M.,University of Illinois at Urbana - Champaign
Hydrology and Earth System Sciences

Water is essential for life. Specifically in the oases of inland arid basins, water is a critically limited resource, essential for the development of the socio-economy and the sustainability of eco-environmental systems. Due to the unique hydrological regime present in arid oases, a moderate groundwater table is the goal of sustainable water management. A shallow water table induces serious secondary salinization and collapse of agriculture, while a deep water table causes deterioration of natural vegetation. From the hydrological perspective, the exchange flux between the unsaturated vadose zone and groundwater reservoir is a critical link to understanding regional water table dynamics. This flux is substantially influenced by anthropogenic activities. In the Tarim River basin of western China, where agriculture consumes over 90% of available water resources, the exchange flux between the unsaturated vadose zone and groundwater reservoir is influenced strongly by irrigation. Recently, mulched drip irrigation, a sophisticated water-saving irrigation method, was widely applied in the Tarim River basin, which greatly impacted the exchange flux and thus the regional groundwater dynamics. Capitalizing on recent progress in evaporation measurement techniques, we can now close the water balance and directly quantify the exchange flux at the field scale, thus gaining a better understanding of regional groundwater dynamics. In this study, comprehensive observations of water balance components in an irrigated cropland were implemented in 2012 and 2013 in a typical oasis within the Tarim River basin. The water balance analysis showed that the exchange flux and groundwater dynamics were significantly altered by the application of water-saving irrigation. The exchange flux at the groundwater table is mostly downward (310.5 mm year-1), especially during drip irrigation period and spring flush period, while the upward flux is trivial (16.1 mm year-1) due to the moderate groundwater table depth (annual average depth 2.9 m). Traditional secondary salinization caused by intense phreatic evaporation (fed by upward exchange flux) is alleviated. However, a new form of secondary salinization may be introduced unwittingly if there is lack of water for periodic flushing, especially when brackish water is used in the irrigation. Furthermore, the water saved via drip irrigation has been used in further growth of irrigated lands instead of supporting the ecological system. This could lead to an increased risk of eco-environmental degradation and calls for improved governance schemes. The insights gained from this study can be potentially applied to other arid inland areas (e.g., central Asia) which face similar water shortages and human development problems. © 2014 Author(s). Source

Hu H.,Tsinghua University | Tian F.,Tsinghua University | Zhang Z.,Tsinghua University | Yang P.,Tsinghua University | And 2 more authors.
Shuili Xuebao/Journal of Hydraulic Engineering

Soil salinity trend is affected by both salt accumulation and leaching during the growth and non-growth periods. To explore the long-term salinization trend of farmland under mulched drip irrigation, the experiments were conducted from 2008 to 2013 in a cotton field in Xinjiang province, northwestern China. More than 15 000 soil samples were collected and tested. With Simultaneous Heat and Water model (SHAW), the salt leaching during the non-growth period was studied. Associated with the soil salt distribution and migration study in the growth period in the other companion papers, the salinization trend in the arid area was evaluated. The results indicate that the salt leaching is obvious in both winter and spring flush. The leaching depth of soil salt is approximately 60 cm in winter flush, which is superior to the spring flush. According to the salt leaching during non-growth period in arid area, soil salinization trend can be controlled and salt balance can be maintained when mulched drip irrigation is adopted in growth period. In consideration of irrigation water amount in growth period only, the water use efficiency (WUE) is 0.68 kg·m-3 and 0.22 kg·m-3 for mulched drip and flood irrigation, respectively. Even if the leaching water amount in non-growth period (375 mm) is taken into account, the WUE of mulched drip irrigation is 0.42 kg·m-3 and still higher than the value of flood irrigation. The results show that in arid and semi-arid areas, the soil salinization trend can be controlled and the WUE will be also improved when the mulched drip irrigation in growth period and the salt leaching measures in non-growth period are both adopted. ©, 2015, Shuili Xuebao/Journal of Hydraulic Engineering. All right reserved. Source

Zhang Z.,Tsinghua University | Hu H.,Tsinghua University | Tian F.,Tsinghua University | Yao X.,Xinjiang Tarim River Basin Management Bureau | Zhong R.,Xinjiang Institute of Ecology and Geography
Journal of Arid Environments

Mulched drip irrigation (MDI) has now become popular in arid and semi-arid areas, under which, however, salts are likely to build up in the surface soil due to deficient leaching water. To explore this new kind of secondary salinization issue, a 3-year experiment was conducted in an arid area in Xinjiang, northwestern China from 2008 to 2011. Over 15,000 soil samples were collected during the experimental years. The patterns of soil salinity distribution under MDI along the horizontal direction as well as vertical direction have been explored. Our results indicate that soil particle size distribution has great impact on soil salt migration and distribution. The salt will build up above the relatively impermeable layer along the soil profile. The zone below drip pipe obtains the lowest salinity level and the salt accumulates in the inter-film zone at the end of growth period. The salinity in the inter-film zone is 1.24-2.34 times the value in the zone below drip pipe within 50cm soil depth, according to the soil texture. Furthermore, our analysis suggests that surface salinity distribution is dominated by MDI while the influence of MDI on salinity distribution is decreasing with the downward distance from ground surface. © 2014 The Authors. Source

Hu H.,Tsinghua University | Zhang Z.,Tsinghua University | Tian F.,Tsinghua University | Yang P.,Tsinghua University | And 2 more authors.
Qinghua Daxue Xuebao/Journal of Tsinghua University

Mulched drip irrigation has gradually replaced flood irrigation and is now widely used in Xinjiang. This study explores the effects of the irrigation methods on the soil salt dynamics and the crop growth using experiments conducted from 2011 to 2012 in a cotton field with mulched drip and flood irrigation systems. The 6 900 samples was observed. The results show that the salinity increased during the growth period by 25% within the top 50 cm of the soil depth with mulched drip irrigation. With flood irrigation, the soil salinity markably decreased due to the large amount of irrigation water. The salt leaching depth was 50 cm for drip irrigation, but more than 150 cm for flood irrigation. The root density with drip irrigation was 1.6 times that of flood irrigation. The water use efficiency was 0.68 kg/m3 with mulched drip irrigation and 0.22 kg/m3 with flood irrigation. Thus, the mulched drip irrigation significantly enhances the water use efficiency; however, the salinization risk induced by the lack of leaching water must also be addressed. © 2016, Tsinghua University Press. All right reserved. Source

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