Abstract:The Tarim River, the longest dryland river in an extremely arid region of China, has undergone ever-increasing human impacts over recent centuries (particularly since the late 1950s during which time large-scale land reclamation in the basin has taken place). Historical literature/maps, gauged hydrological data and satellite images were analyzed to examine how the river network evolution in the basin and the fluvial morphology of the main stem of the Tarim River have responded to human influences. The results … Show more
“…Using discharge intervals of Q = 50 m 3 /s and 40 m 3 /s for AL and XQM, respectively, Figure shows distributions for f(Q), P(SSL), and Qs within each interval class. Consistent with the results in table 1 in Yu et al () and many others (e.g., Wolman & Miller, ), the distributions of f(Q) and P(SSL) at AL and XQM clearly show that low flow events occur more frequently but transport less sediment than moderate–high flow events.…”
Section: Resultssupporting
confidence: 89%
“…Conversely, discharge at AL and XQM stations is highly variable and shows a very large range between maximum and minimum values (c.f. table 1 in Yu, Disse, Huang, Yu, & Li, ). The mean discharge (Q m , 148.7 and 118.6 m 3 /s for AL and XQM, respectively) is significantly higher than the median (Q 50 , 60.7 and 45.0 m 3 /s for AL and XQM, respectively); along with high positive skewness (CS), this indicates that the discharge distribution for the Tarim River is asymmetric, that is, low‐flow events occur more frequently than moderate and high flow events.…”
Section: Resultsmentioning
confidence: 99%
“…As with the discharge distribution, the mean daily SSC for all months, whether during the flood season or not, is higher than the median and, indeed, many SSC values surpass the upper fence (Q3 + 1.5 IQR, Figure , the interquartile range IQR=Q3‐Q1, Q3 is third quartile and Q1 is the first quartile). This indicates that the SSC distribution is non‐symmetric and concentrated toward lower values (that is, the tail on the right side of the SSC distribution is longer or fatter than the left side), which is also consistent with positive skewness (c.f., Yu et al, ).…”
Despite a growing interest in the sediment dynamics of dryland rivers, most research has been based on ephemeral streams in endogenic hydrological systems (runoff and sediment transport determined by local precipitation). Less attention, however, has been paid to allogenic and perennial dryland rivers. Here, we report a case study on the suspended sediment dynamics of the Tarim River, an allogenic and perennial river flowing in a very arid environment in China, based on mean daily discharge and mean daily suspended sediment concentration (SSC) over the last 5 decades . Results reveal that discharge and SSCs are predominantly low and have distributions with large positive skewness. The SSC-discharge relationships can be fairly well generalized by power functions, with quite large scatter at extreme (low and high) flow conditions. Marked temporal and spatial variations were observed in the effective discharge for sediment transport. The frequency of the effective discharge ranged from 0.5% to 2% (or an average flow duration of 2-7 days/year), implying that moderate to high flows play an important role in sediment transport. The sediment rating curves show strong hysteresis effects, with 3 types of hysteresis loops observed, clockwise (the most predominant), anticlockwise, and figure of eight. The high potential for bank collapse near the peak and falling limb of the flood hydrograph is the major cause of anticlockwise and figure-of-eight hysteresis loops.
“…Using discharge intervals of Q = 50 m 3 /s and 40 m 3 /s for AL and XQM, respectively, Figure shows distributions for f(Q), P(SSL), and Qs within each interval class. Consistent with the results in table 1 in Yu et al () and many others (e.g., Wolman & Miller, ), the distributions of f(Q) and P(SSL) at AL and XQM clearly show that low flow events occur more frequently but transport less sediment than moderate–high flow events.…”
Section: Resultssupporting
confidence: 89%
“…Conversely, discharge at AL and XQM stations is highly variable and shows a very large range between maximum and minimum values (c.f. table 1 in Yu, Disse, Huang, Yu, & Li, ). The mean discharge (Q m , 148.7 and 118.6 m 3 /s for AL and XQM, respectively) is significantly higher than the median (Q 50 , 60.7 and 45.0 m 3 /s for AL and XQM, respectively); along with high positive skewness (CS), this indicates that the discharge distribution for the Tarim River is asymmetric, that is, low‐flow events occur more frequently than moderate and high flow events.…”
Section: Resultsmentioning
confidence: 99%
“…As with the discharge distribution, the mean daily SSC for all months, whether during the flood season or not, is higher than the median and, indeed, many SSC values surpass the upper fence (Q3 + 1.5 IQR, Figure , the interquartile range IQR=Q3‐Q1, Q3 is third quartile and Q1 is the first quartile). This indicates that the SSC distribution is non‐symmetric and concentrated toward lower values (that is, the tail on the right side of the SSC distribution is longer or fatter than the left side), which is also consistent with positive skewness (c.f., Yu et al, ).…”
Despite a growing interest in the sediment dynamics of dryland rivers, most research has been based on ephemeral streams in endogenic hydrological systems (runoff and sediment transport determined by local precipitation). Less attention, however, has been paid to allogenic and perennial dryland rivers. Here, we report a case study on the suspended sediment dynamics of the Tarim River, an allogenic and perennial river flowing in a very arid environment in China, based on mean daily discharge and mean daily suspended sediment concentration (SSC) over the last 5 decades . Results reveal that discharge and SSCs are predominantly low and have distributions with large positive skewness. The SSC-discharge relationships can be fairly well generalized by power functions, with quite large scatter at extreme (low and high) flow conditions. Marked temporal and spatial variations were observed in the effective discharge for sediment transport. The frequency of the effective discharge ranged from 0.5% to 2% (or an average flow duration of 2-7 days/year), implying that moderate to high flows play an important role in sediment transport. The sediment rating curves show strong hysteresis effects, with 3 types of hysteresis loops observed, clockwise (the most predominant), anticlockwise, and figure of eight. The high potential for bank collapse near the peak and falling limb of the flood hydrograph is the major cause of anticlockwise and figure-of-eight hysteresis loops.
“…The average annual temperature is about 10.6 °C to 11.5 °C with monthly mean temperature ranging from 20 °C to 30 °C in July and −10 °C to −20 °C in January 26 . Compared to the average annual precipitation of 200–300 mm in the mountainous headwater regions 37 , the average annual precipitation at the mainstream area of the Tarim River is only about 50–80 mm. The annual potential evaporation ranges from 2000 mm to 2900 mm.Figure 8Sketch map of the Tarim River Basin and locations of hydrologic stations.…”
The Tarim River is the longest inland river at an arid area in China. Deterioration in its ecohydrological system has received much attention world widely. This study presents quantitative assessment of hydrological alterations in the hydrological regime of the Tarim River caused by reservoir irrigation and channel irrigation over a period of over a half century. The improved indicators of hydrologic alteration and range of variability approach were applied to the daily flow rates at the two representative hydrological stations. Our study shows that the annual extreme water conditions (1-, 3-, 7-day annual minimum and extreme low timing) have been altered, compared with the pre-impact period. The average flow rate in July, the 30-day annual maximum flow rates, the date for the maximum rate, the rise rate, and the fall rate show a significant decreasing trend. The improved overall degree of hydrological alteration for the two stations are approximately 68.7% and 61.8%, suggesting a high degree of alteration. This study greatly improved our understanding of impacts of irrigations on the ecohydrological characteristics in the Tarim River.
“…Elevation map of the Tarim Basin based on Shuttle Radar Topography Mission data (USGS, 2004) with historically documented rivers. The rivers of the Qing Dynasty are fromYang, Liu, et al (2006), and those of the Han Dynasty are fromYu et al (2016).…”
Sediment provenance is a key issue in understanding the aeolian system of the Taklamakan Desert, an important source of global dust and the largest sand sea in the midlatitudes worldwide. In provenance research, it may be a mistake to assume that the sand and dust fractions of desert sediments have the same source, which has been the case in previous studies of the Taklamakan Desert. The aims of the present study were to identify the provenance of the sand and dust fractions of the sediments of the Taklamakan Desert, to determine the contemporary sediment supply mechanisms of the desert, and to assess the relative importance of silt‐producing mechanisms for the desert dust. We analyzed the grain size of desert sediment samples and measured the content of major, trace, and rare earth elements within the bulk samples, sand fractions (>63 μm), and dust fractions (<63 μm). Our grain size and geochemical data sets suggest that the Kunlun Mountains are the main source of the sand fraction, whereas both the Kunlun and Tian Shan Mountains are the main sources of the dust fraction. Our interpretation is supported by the elevation gradient within the Taklamakan Desert and by wind data.
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