Reach and catchment-scale influences on invertebrate assemblages in a river with naturally high fine sediment loads

In South Africa, as in many developing countries, the suspended sediment (SS) data required to support catchment scale hillslope restoration and rehabilitation programmes are typically scarce or absent, leading to a reliance on modelled SS loads and yields that are generally not validated by measured SS data. An exception is the Tsitsa River catchment in the Eastern Cape Province, where modelled SS yields were high (21 &#8211; 50 t/ha/yr), leading to the establishment of a Citizen Technician-based monitoring programme (2015 &#8211; 2019) that has provided flood-focused, sub-catchment scale SS data at sub-daily timestep for 11 sites throughout the 4000 km2 catchment.A confluence-based SS fingerprinting and tracing exercise was undertaken in the catchment (2018). Analysis of the distinctive physicochemical properties of resuspended fine sediment sampled above and below major confluences allowed the percentage of SS contributed by each tributary to be apportioned, and compared with findings from both the SS monitoring campaign and from existing models.

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Effects of flow and fine sediment dynamics on the turnover of stream invertebrate assemblages

Ecohydrology ◽

10.1002/eco.1443 ◽

2013 ◽

pp. n/a-n/a ◽

Cited By ~ 11

Author(s):

Cristina Buendia ◽

Chris N. Gibbins ◽

Damià Vericat ◽

Ramon J. Batalla

Keyword(s):

Fine Sediment ◽

Sediment Dynamics ◽

Invertebrate Assemblages

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Potential impacts of a future Nordic bioeconomy on surface water quality

AMBIO ◽

10.1007/s13280-020-01355-3 ◽

2020 ◽

Vol 49 (11) ◽

pp. 1722-1735 ◽

Cited By ~ 6

Author(s):

Hannu Marttila ◽

Ahti Lepistö ◽

Anne Tolvanen ◽

Marianne Bechmann ◽

Katarina Kyllmar ◽

...

Keyword(s):

Climate Change ◽

Water Quality ◽

Ecosystem Services ◽

Multiple Stressors ◽

Ecological Status ◽

Surface Water Quality ◽

Mitigation Measures ◽

Catchment Management ◽

Catchment Scale ◽

Sediment Loads

Abstract Nordic water bodies face multiple stressors due to human activities, generating diffuse loading and climate change. The ‘green shift’ towards a bio-based economy poses new demands and increased pressure on the environment. Bioeconomy-related pressures consist primarily of more intensive land management to maximise production of biomass. These activities can add considerable nutrient and sediment loads to receiving waters, posing a threat to ecosystem services and good ecological status of surface waters. The potential threats of climate change and the ‘green shift’ highlight the need for improved understanding of catchment-scale water and element fluxes. Here, we assess possible bioeconomy-induced pressures on Nordic catchments and associated impacts on water quality. We suggest measures to protect water quality under the ‘green shift’ and propose ‘road maps’ towards sustainable catchment management. We also identify knowledge gaps and highlight the importance of long-term monitoring data and good models to evaluate changes in water quality, improve understanding of bioeconomy-related impacts, support mitigation measures and maintain ecosystem services.

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The difference of sediment sources between high flows and low flows in the Hailuogou Glacier stream

10.5194/egusphere-egu2020-13337 ◽

2020 ◽

Author(s):

Jiacun Chen ◽

Ivan Lizaga ◽

Xinbao Zhang ◽

Ana Navas

Keyword(s):

Suspended Sediment Concentration ◽

Sediment Load ◽

Sediment Concentration ◽

Fine Sediment ◽

High Flow ◽

Sediment Sources ◽

Low Flows ◽

Sediment Loads ◽

High Flows ◽

Sediment Mixtures

&#160; &#160; &#160; &#160;In the area of Mt Gongga (Hengduan range, China) most glaciers are experiencing considerable retreat and mass loss since the early 20th century. Drainage of recently deglaciated surfaces delivers fine sediments thus affecting patterns of sediment delivery with impacts on water quality. Research in the area indicates significant differences between sediment at high flows and low flows in the same river during different seasons. High level flows were usually caused by heavy rainfall events or continuous rainfall that erode the slopes by sheet, rill and gully erosion and transport important amounts of sediments to streams leading to significant increases in river sediment flux. During low flows subsurface soil flux during spring and the direct discharge at the outlet of the glacier result in much less sediment load and mean suspended sediment concentration compared with high flows. The runoff volume, hydrograph peak, sediment load and mean suspended sediment concentration in high flows are as much as an order of magnitude higher than in low flows. Therefore, it is of great significance exploring the provenance of fine sediment during high flows and low flows to assess if there are differences in the contributing sources of sediments.&#160; &#160; &#160; &#160; &#160; For this purpose during a 2 weeks field campaign in May 2016 in the frame of IAEA INT5153 project, source sediment samples and channel bed sediment mixtures were collected along the river valley of the Hailuogou Glacier. Three main sources were identified: surface glacier materials, old moraines and recent moraines. Composite surface samples (2 cm) were created of 10 subsamples in each representative site for surface glacier materials. Following the same scheme on old lateral moraines 10 sites were selected from the more mineral blocky deposits to the most vegetated parts at higher altitudes. On recent moraines 12 sites with different stages of vegetation cover were sampled. Starting from the glacier tongue a total of 7 fine sediment mixtures were collected along the river of which 3 composite samples corresponded to the dry season with low flow and 4 samples corresponded to high flow.&#160; A new consensus test method and an unmixing model were used to estimate the apportionments of the sediment sources to the sediment loads. The results showed that the contribution of different sources to the sediment mixture deposits varied along the river showing different provenance for the low and high flow suggesting different mechanisms of sediment generation during melting and dry seasons. This study is of interest for gaining knowledge on changing dynamics of sediment in regions were the rapid disappearance of glaciers and snow as in Mt. Gongga, has increased the mobilization and transport of sediment loads with consequences for the local population.

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SEPAL – a simple GIS-based tool to estimate sediment pathways in lowland catchments

Advances in Geosciences ◽

10.5194/adgeo-21-25-2009 ◽

2009 ◽

Vol 21 ◽

pp. 25-32 ◽

Cited By ~ 13

Author(s):

J. Kiesel ◽

B. Schmalz ◽

N. Fohrer

Keyword(s):

Fine Sediment ◽

Successful Implementation ◽

River Bank ◽

Sediment Loads ◽

Sediment Input ◽

Regression Approach ◽

The Individual ◽

Comparison Of The Results ◽

Annual Sediment ◽

River Banks

Abstract. Even though soil loss in the lowlands imposes not as much a restriction on land use and agricultural productivity as in erosion affected mountainous areas, the input of fine sediment into the rivers and streams is a concern due to water quality issues and substrate siltation. Drains, river banks and agricultural fields are the three main sources of fine sediment in lowland regions. For a successful implementation of measures to decrease sediment input a well-founded knowledge of the individual entry pathways is essential. To assess the importance of possible entry pathways, a GIS based methodology (SEPAL) has been established combining the ABAG, a river bank erosion formula and a regression approach to include the contributions of drains. SEPAL has been applied on a study catchment in Northern Germany. The results show that 15% of the sediment input into the river comes from agricultural drains, 71% from river banks and 14% from adjacent fields. A comparison of the results with field-mapping and -sampling shows that the approach is plausible. The calculated total annual sediment input is 616 t yr−1, while the measured suspended sediment load is 636 t yr−1. It can be concluded that the methodology is suitable for estimating sediment entry pathways and annual sediment loads in lowland catchments as a base for modelling projects and further investigations. However, further work is necessary for gaining sound knowledge about uncertainties and especially about the processes forcing sediment input from drains.

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