/pdf/suspended-sediment-transport-dynamics-in-rivers-multi-scale-6oi6e6ar7w.pdf

Suspended sediment transport dynamics in rivers: Multi-scale drivers of temporal variation

River suspended sediment modelling using the CART model: A comparative study of machine learning techniques.

Climatic or regionally induced by humans? Tracing hydro-climatic and land-use changes to better understand the Lake Urmia tragedy

Spatiotemporal variability of climate and streamflow in the Songhua River Basin, northeast China

Sediment-discharge hysteresis loops are frequently analyzed to facilitate the understanding of sediment transport processes. Hysteresis patterns, however, are often complex and their interpretation can be complicated. Particularly, quantifying hysteresis patterns remains a problematic issue. Moreover, it is currently unknown how much data is required for analyzing sediment-discharge hysteresis loops in a given area. These open questions and challenges motivated us to develop a new method for quantifying suspended-sediment hysteresis. Subsequently, we applied the new hysteresis index to three suspended-sediment and discharge datasets from a small tropical rainforest catchment. The datasets comprised a different number of events and sampling sites. Our analyses show three main findings: (1) datasets restricted to only few events, which is typical for rapid assessment surveys, were always sufficient to identify the dominating hysteresis pattern in our research area. Furthermore, some of these small datasets contained multiple-peak events that allowed identifying intra-event exhaustion effects and hence, limitations in sediment supply. (2) Datasets comprising complete hydrological years were particularly useful for analyzing seasonal dynamics of hysteresis. These analyses revealed an exhaustion of hysteresis on the inter-event scale which also points to a limited sediment supply. (3) Datasets comprising measurements from two consecutive gauges installed at the catchment outlet and on a slope within that catchment allowed analyzing the change of hysteresis patterns along the flowpath. On the slope, multiple-peak events showed a stronger intra-event exhaustion of hysteresis than at the catchment outlet. Furthermore, exhaustion of hysteresis on the inter-event scale was not evident on the slope but occurred at the catchment outlet. Our results indicate that even small sediment datasets can provide valuable insights into sediment transport processes of small catchments. Furthermore, our results may serve as a first guideline on what to expect from an analysis of hysteresis patterns for datasets of varying quality and quantity.

Quantification and interpretation of suspended-sediment discharge hysteresis patterns: How much data do we need?

Based on the long-term hydrological and meteorological series. DEM, soil database and documents of soil conservation measures of the middle Yellow River, investigations are made on the spatial and temporal changes of runoff and the impact of 11 factors, which include rainfall, temperature, terrain slope, drainage density, gravel, sand, silt, and organic carbon content in soil, water consumption, and soil conservation measures. The results show that the total runoff generated from the middle Yellow River had a decreasing trend in the past 60 years, with two abrupt falls around the years 1971 and 1991. In the spatial dimension, runoff modulus grew from the north to the south and from the west to the east, and the largest gradient of spatial change of runoff modulus happened during the period of 1956-1970 before the first falls of the total runoff. In the period 1954-2009. the average annual rate of temporal change of runoff modulus increased acceleratedly outward from the northwest of the middle Yellow River with a concentric ring pattern. Correlation analysis of runoff modulus with potential influencing factors in the spatial perspective reveals that the spatial distribution of the runoff modulus is principally the results of the regional variation of natural conditions. The results of the correlation analysis of the temporal series of runoff coefficient and influencing factors suggest that climate change, hydraulic engineering and soil conservation measures, were all the major causes of runoff reducing in the second half of the last century in the middle Yellow River. For the whole middle Yellow River, climate change contributed over 40% of the runoff deviations in the 1960s, 1970s and 1990s. while water consumption induced also over 40% runoff reduction in the 1960s. 1970s and 1980s. The runoff reduction due to hydraulic engineering was about 2-3 times of that caused by soil conservation measures, and both of them increased continuously from the 1960s to the 1980s, and kept at a higher level in the 1990s. The contribution of different causes to runoff deviation was variable in different drainage areas. Generally, in the semi-arid areas climate change played a decreasing role in runoff reduction comparing with other causes, while in the semi-humid areas it induced a higher and more variable proportion of runoff deviation according to the decade means. (C) 2012 Elsevier B.V. All rights reserved.

A study on the annual runoff change and its relationship with water and soil conservation practices and climate change in the middle Yellow River basin

Sediment rating curves in the Ningxia-Inner Mongolia reaches of the upper Yellow River and their implications

article i nfo Suspended sediment dynamics are still imperfectly understood, especially in the upper Yellow River where few studies on this issue have been conducted. This study analyzed the variability in suspended sediment concentration at different temporal scales (within-flood, monthly-seasonal and annual). Using a dataset up to 49 years long (1954-2002) at Toudaoguai station, this paper provided insight into the characteristics of suspended sediment transport in the Ningxia-Inner Mongolia reaches of the upper Yellow River. The results show that, in a single flood event, changes in SSC are not simultaneous with changes in discharge, resulting in counterclockwise hysteretic loops, clockwise loops or figure-eight loops. The C-Q loops and sediment rating curves for different seasons had different characters. The diversiform C-Q loops in the Inner Mongolia reaches of the upper Yellow River may be mainly caused by the sediment inputs from tributaries, the differ- ent propagation velocity of sediment and water discharge, spatial and temporal storage-depletion processes of available sediment. At annual scale, the variations of annual mean discharge and SSC displayed a similar gradually deceasing trend, and the relation between water discharge and SSC during 1954-2002 could be de- scribed by a cubic polynomial function. Since the joint operation of Liujiaxia and Longyangxia reservoirs after 1986, the transport capacity of the Upper Yellow River has been much reduced.

The suspended sediment dynamics in the Inner-Mongolia reaches of the upper Yellow River

In recent years, climate change and anthropogenic activities have threatened the water supply in the middle reaches of the Yellow River, prompting this study into the variation of water resources and the influencing factors, taking the Huangfuchuan basin as an example. Firstly, changes in climatic aridity and annual runoff in the Huangfuchuan basin from 1956 to 2009 were analysed. Then, the influence of changes in climatic aridity, water use for irrigation and soil conservation measures were calculated using an analysis of principal components regression. The results show that climatic aridity has increased in the recent three decades with two abrupt changes around 1961 and 1998, and that annual runoff has decreased continually with two abrupt changes around 1979 and 1999. The rapid development of sediment check dams in the 1970s could be the reason for the abrupt change around 1979. The abrupt change around 1999 could be the result of both the intensification of changes in climatic aridity and the large-scale construction of water and soil conservation measures after 1983, the further improvement of these measures after 1993 and ecological restoration measures of converting cropland to forest implemented since 1997. By quantifying the effects of those factors that influence runoff variation, it was found that anthropogenic activities were more important than climate change in the two periods between 1979–1998 and 1999–2006, but the influence of changes in climatic aridity increased from the first to the second period. For the runoff reduction related to anthropogenic activities, the primary cause was water diversion for irrigation in the first period, and it was soil conservation measures in the second period.

/pdf/the-influence-of-climate-change-and-anthropogenic-activities-qpe1vr99q4.pdf

The influence of climate change and anthropogenic activities on annual runoff of Huangfuchuan basin in northwest China

Based on the MK test and RUSLE model, changes in the soil erosion and sediment yield of the Xiliugou basin in the upper Yellow River during the period 1960–2013 were studied. The results indicate that hyperconcentrated floods are very typical in the Xiliugou basin. Hyperconcentrated floods occurred in 87.1% of the years during the period 1960–1990. Since the 2000s, the number of such floods was reduced considerably with the application of soil and water conservation, and only one hyperconcentrated flood was recorded from 2006 to 2013. Hyperconcentrated flows transfer most of the sediment yield in the Xiliugou basin. The sediment load carried by hyperconcentrated floods accounted for 84.7% of the total sediment yield in that basin during the period 1964–1990. Because hyperconcentrated flows may cause high and intensive erosion, the sediment eroded in gullies may be the main sediment source in the basin. Our results show that the percentages of gully erosion and slope erosion in this basin in the period 1964–1990 were 76.1% and 23.9%, respectively. A daily rainfall larger than 12 mm can cause hyperconcentrated flows, and the frequency of hyperconcentrated floods increases with the rainfall intensity. As a result of vegetation recovery and check-dam building, the frequency of hyperconcentrated flows and the annual sediment concentration and sediment yield for the same intensity of rainstorms were noticeably lower from 2006 to 2013 than those from 1964 to 1990. From 1960 to 2013, the annual sediment yield of the basin showed a significant downward trend, whereas no significant trend was detected in the annual precipitation. The annual sediment yield and precipitation from 1999 to 2013 decreased by 82.1% and 1.7%, respectively, compared with those in the period 1960–1998. The implementation of water and soil conservation measures and the reduced frequency of hyperconcentrated floods were the main reasons for the significant reduction in sediment yield in the period 2006–2013.

Wenwei Shao

Papers

A study on the annual runoff change and its relationship with water and soil conservation practices and climate change in the middle Yellow River basin

Sediment rating curves in the Ningxia-Inner Mongolia reaches of the upper Yellow River and their implications

The suspended sediment dynamics in the Inner-Mongolia reaches of the upper Yellow River

The influence of climate change and anthropogenic activities on annual runoff of Huangfuchuan basin in northwest China

Changes and influencing factors of the sediment load in the Xiliugou basin of the upper Yellow River, China