首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Influence of the rainfall regime on erosion and transfer of suspended sediment in a 905‐km² mountainous catchment of the southern French Alps was investigated by combining sediment monitoring, rainfall data, and sediment fingerprinting (based on geochemistry and radionuclide concentrations). Suspended sediment yields were monitored between October 2007 and December 2009 in four subcatchments (22–713 km²). Automatic sediment sampling was triggered during floods to trace the sediment origin in the catchment. Sediment exports at the river catchment outlet (330 ± 100 t km‐2 yr‐1) were mainly driven (80%) by widespread rainfall events (long duration, low intensities). In contrast, heavy, local and short duration storms, generated high peak discharges and suspended sediment concentrations in small upstream torrents. However, these upstream floods had generally not the capacity to transfer the sediment down to the catchment outlet and the bulk of this fine sediment deposited along downstream sections of the river. This study also confirmed the important contribution of black marls (up to 70%) to sediment transported in rivers, although this substrate only occupies c. 10% of the total catchment surface. Sediment exports generated by local convective storms varied significantly at both intra‐ and inter‐flood scales, because of spatial heterogeneity of rainfall. However, black marls/marly limestones contribution remained systematically high. In contrast, widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones/marls, Quaternary deposits and conglomerates, which corroborates the results of a previous sediment fingerprinting study conducted on riverbed sediment. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

2.
Cultivated fields have been shown to be the dominant sources of sediment in almost all investigated UK catchments, typically contributing 85 to 95% of sediment inputs. As a result, most catchment management strategies are directed towards mitigating these sediment inputs. However, in many regions of the UK such as the Nene basin there is a paucity of sediment provenance data. This study used the caesium‐137 (137Cs) inventories of lake and floodplain cores as well as the 137Cs activities of present day sediment to determine sediment provenance. Sediment yields were also reconstructed in a small lake catchment. Low 137Cs inventories were present in the lake and floodplain cores in comparison to the reference inventory and inventories in cores from other UK catchments. Caesium‐137 activities in the present day sediments were low; falling close to those found in the channel bank catchment samples. It was estimated that 60 to 100% of the sediment in the Nene originated from channel banks. Pre‐1963 sediment yields were approximately 11.2 t km?2 yr?1 and post‐1963 was approximately 11.9 t km?2 yr?1. The lack of increased sediment yield post‐1963 and low sediment yield is unusual for a UK catchment (where a yield of 28 to 51 t km?2 yr?1 is typical for a lowland agricultural catchment), but is explained by the low predicted contribution of sediment from agricultural topsoils. The high channel bank contribution is likely caused by the river being starved of sediment from topsoils, increasing its capacity to entrain bank material. The good agreement between the results derived using cores and recently transported sediments, highlight the reliability of 137Cs when tracing sediment sources. However, care should be taken to assess the potential impacts of sediment particle size, sediment focusing in lakes and the possible remobilization of 137Cs from sedimentary deposits. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

3.
H. Marttila  B. Kløve 《水文研究》2014,28(17):4756-4765
Lowland catchments in Finland are intensively managed, promoting erosion and sedimentation that negatively affects aquatic environments. This study quantified fine‐grained bed sediment in the main channel and upstream headwaters of the River Sanginjoki (399.93 km2) catchment, Northern Finland, using remobilization sediment sampling during the ice‐free period (May 2010–December 2011). Average bed sediment storage in river was 1332 g m?2. Storage and seasonal variations were greater in small headwater areas (total bed sediment storage mean 1527 g m?2, range 122–6700 g m?2 at individual sites; storage of organic sediment: mean 414 g m?2, range 27–3159 g m?2) than in the main channel (total bed sediment storage: mean 1137 g m?2, range 61–4945 g m?2); storage of organic sediment: mean 329 g m?2, range 13–1938 g m?2). Average reach‐specific bed sediment storage increased from downstream to upstream tributaries. In main channel reaches, mean specific storage was 8.73 t km?1, and mean specific storage of organic sediment 2.45 t km?1, whereas in tributaries, it was 126.94 and 34.05 t km?1, respectively. Total fine‐grained bed sediment storage averaged 563 t in the main channel and 6831 t in the catchment. The proportion of mean organic matter at individual sites was 15–47% and organic carbon 4–455 g C m?2, with both being highest in small headwater tributaries. Main channel bed sediment storage comprised 52% of mean annual suspended sediment flux and stored organic carbon comprised 7% of mean annual total organic carbon load. This indicates the importance of small headwater brooks for temporary within‐catchment storage of bed sediment and organic carbon and the significance of fine‐grained sediment stored in channels for the suspended sediment budget of boreal lowland rivers. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

4.
Upland erosion and the resulting reservoir siltation is a serious issue in the Isábena catchment (445 km2 Central Spanish Pyrenees). During a three‐month period, water and sediment fluxes have been monitored at the catchment outlet (Capella), two adjacent subcatchments (Villacarli, 41 km2; Cabecera, 145 km2) and the elementary badland catchment Torrelaribera (8 ha). This paper presents the results of the monitoring, a method for the calculation of a sedigraph from intermittent measurements and the derived sediment yields at the monitored locations. The observed suspended sediment concentrations (SSCs) demonstrate the role of badlands as sediment sources: SSCs of up to 280 g l?1 were encountered for Villacarli, which includes large badland areas. SSCs at the Cabecera catchment, with great areas of woodland, barely exceeded 30 g l?1. SSCs directly at the sediment source (Torrelaribera) were comparable to those at Villacarli, suggesting a close connection within this subcatchment. At Capella, SSCs of up to 99 g l?1 were observed. For all sites, SSC displayed only a loose correlation with discharge, inhibiting the application of a simple sediment rating curve. Instead, ancillary variables acting as driving forces or proxies for the processes (rainfall energy, cumulative discharge, rising/falling limb data) were included in a quantile regression forest model to explain the variability in SSC. The variables with most predictive power vary between the sites, suggesting the predominance of different processes. The subsequent flood‐based calculation of sediment yields attests high specific sediment yields for Torrelaribera and Villacarli (6277 and 1971 t km?2) and medium to high yields for Cabecera and Capella (139 and 410 t km?2) during the observation period. In all catchments, most of the sediment was exported during intense storms of late summer. Later flood events yield successively less sediment. Relating upland sediment production to yield at the outlet suggests considerable effects of sediment storage within the river channel. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

5.
In response to the potential shortcomings of single-technique strategies in the investigation of erosion and sedimentation, a combined magnetic and radiometric (13Cs and 210Pb) approach has been undertaken in the upland, watershed-lake system of Howden Reservoir, Derbyshire. By combining these techniques, some assessment of sediment sources and the erosion status of the catchment has been achieved. Alone, each approach would have been unable to determine unequivocally sediment provenance. Furthermore, the parallel use of these measurements has highlighted limitations and/or uncertainties in both the magnetic and 137Cs techniques. These problems reflect the particular soil characteristics and drainage conditions of this upland catchment. Despite the documented severity of peat erosion in the region, Howden Reservoir has a mixture of sediment sources and a relatively moderate rate of sedimentation. Sediment yields (total 127·7 t km?2 yr?1 including organic fraction 31·3 t km?2 yr?1) are, however, higher than in other British upland areas.  相似文献   

6.
Among the different controls of erosion budget at basin level, the relative impact of dams and land management is yet to be investigated. In this paper, the impact of dams on sediment yield has been assessed by using a conceptual modelling framework which considers the gross erosion and the cascade of dams constructed on a river network. The sediment budget has been estimated based on the gross erosion, deposition of sediment in reservoirs, and sediment yields of 23 mainland river basins of India. The gross erosion of the country is estimated as 5.11 ± 0.4 Gt yr?1 or 1559 t km?2 yr?1, out of which 34.1 ± 12% of the total eroded soil is deposited in the reservoirs, 22.9 ± 29% is discharged outside the country (mainly to oceans), and the remaining 43.0 ± 41% is displaced within the river basins. The river basins of northern India contribute about 81% of the total sediment yield from landmass while the share of southern river basins is 19%. The components of revised sediment budget for India are prominently influenced by the sediment trapped in reservoirs and the treatment of catchment areas by soil and water conservation measures. Analysis of sediment deposition in 4937 reservoirs indicated the average annual percentage capacity loss as 1.04% though it varies from 0.8% to >2% per year in smaller dams (1–50 Mm3 capacity) and from <0.5% to 0.8% per year in larger dams (51 to >1000 Mm3 capacity). Siltation of smaller dams poses a serious threat to their ecosystem services as they cater to a wider population for domestic, agricultural, and industrial purposes. Amongst the environment controls, land use significantly impacts the gross erosion rate and specific sediment yield as compared to climatic and topographic parameters. However, to analyse their integrated effect on the complex processes of sediment fluxes in a basin, further research efforts are needed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

7.
Rainfall, peak discharges, and suspended sediment transport were surveyed for 280 events in three small (0.8 to 10 km2) catchments in a hilly area derived from Neogene marls, silts, and sands. Under similar hydrological input conditions, stream flow behaviour and sediment delivery differed considerably from one catchment to another, depending on topography, lithology, land use, and especially sediment availability. Analytical treatment of data showed a good fit between sediment yield and peak flow discharge. Less good, although still significant, was the correlation between sediment concentration and discharge values for different flow stages. Rainfall peak/basin lag time and rainfall/discharge showed poor or no correlation, mainly due to strong variations in rainfall distribution. Sediment concentration in the catchments varied enormously according to season, from zero up to 334 g 1?1; sediment yield was 160-900 tonnes km?2 yr?1 in the two major catchments, and over 5200 tonnes km?2 yr?1 in the headwater catchment, stressing the importance of small tributaries not only in inducing floods in downstream channels, but also in sediment supply.  相似文献   

8.
《水文科学杂志》2013,58(4):619-635
Abstract

The drawdown of Crombie Reservoir in November 2001 afforded the opportunity to examine the exposed sediments trapped since impoundment in 1868. Direct measurements of infill depth enabled an isopachyte map to be produced. Gravimetric conversion using measured bulk densities and a trap efficiency term indicated a long-term catchment sediment yield of 59.1 t km?2 year?1. Core stratigraphy analysis indicated that sediments were dark brown/black cohesive silty-muds with multiple sandy sub-units, representing a combination of discrete flood events and previous drawdown surfaces. Dating, constrained by mineral magnetic and 137Cs analysis, indicated that sedimentation rates have varied from 0.2 to 0.8 g cm?2 year?1, corresponding to a four-fold variation in catchment sediment yield (approximately 20–93 t km?2 year?1), most likely controlled by extensive conversion of moorland to woodland, and post-World War II agricultural expansion. The Crombie investigation is combined with other reservoir sedimentation surveys within the Midland Valley of Scotland. Area-specific sediment yields (t km?2 year?1) evidence a weak, though statistically significant (p > 0.05), positive correlation with catchment area (km2). The increase in area-specific yield with catchment area contradicts the decline, which is generally expected, and is taken to reflect the significance of channel erosion within water supply basins featuring mainly natural and semi-natural vegetation cover and low-intensity land management practices. With stable slopes channel erosion dominates and area-specific sediment yield increases downstream due to greater entrainment and transport potential. The high degree of scatter in the Midland Valley database reflects significant variations in the extent of land-use change and the local importance of agricultural improvements and afforestation practices.  相似文献   

9.
Seasonal suspended sediment transfer in glaciated catchments is responsive to meteorological, geomorphological, and glacio-fluvial conditions, and thus is a useful indicator of environmental system dynamics. Knowledge of multifaceted fluvial sediment-transfer processes is limited in the Alaskan Arctic – a region sensitive to contemporary environmental change. For two glaciated sub-catchments at Lake Peters, northeast Brooks Range, Alaska, we conducted a two-year endeavour to monitor the hydrology and meteorology, and used the data to derive multiple-regression models of suspended sediment load. Statistical selection of the best models shows that incorporating meteorological or temporal explanatory variables improves performances of turbidity- and discharge-based sediment models. The resulting modelled specific suspended sediment yields to Lake Peters are: 33 (20–60) t km−2 yr−1 in 2015, and 79 (50–140) t km−2 yr−1 in 2016 (95% confidence band estimates). In contrast to previous studies in Arctic Alaska, fluvial suspended sediment transfer to Lake Peters was primarily influenced by rainfall, and secondarily influenced by temperature-driven melt processes associated with clockwise diurnal hysteresis. Despite different sub-catchment glacier coverage, specific yields were the same order of magnitude from the two primary inflows to Lake Peters, which are Carnivore Creek (128 km2; 10% glacier coverage) and Chamberlin Creek (8 km2; 23% glacier coverage). Seasonal to longer-term sediment exhaustion and/or contrasting glacier dynamics may explain the lower than expected relative specific sediment yield from the more heavily glacierized Chamberlin Creek catchment. Absolute suspended sediment yield (t yr−1) from Carnivore Creek to Lake Peters was 27 times greater than from Chamberlin Creek, which we attribute to catchment size and sediment supply differences. Our results provide a foundational understanding of the current sediment transfer regime and are useful for predicting changes in fluvial sediment transport in glaciated Alaskan Arctic catchments.  相似文献   

10.
Sediment yield can be a sensitive indicator of catchment dynamics and environmental change. For a glacierized catchment in the High Arctic, we compiled and analyzed diverse sediment transfer data, spanning a wide range of temporal scales, to quantify catchment yields and explore landscape response to past and ongoing hydroclimatic variability. The dataset integrates rates of lake sedimentation from correlated varve records and repeated annual and seasonal sediment traps, augmented by multi‐year lake and fluvial monitoring. Consistent spatial patterns of deposition enabled reconstruction of catchment yields from varve‐ and trap‐based fluxes. We used hydroclimatic data and multivariate modeling to examine annual controls of sediment delivery over almost a century, and to examine shorter‐term controls of sediment transfer during peak glacier melt. Particle‐size analyses, especially for annual sediment traps, were used to further infer sediment transfer mechanisms and timing. Through the Medieval Warm Period and Little Ice Age, there were no apparent multi‐century trends in lake sedimentation rates, which were over three times greater than those during the mid‐Holocene when glaciers were diminished. Twentieth‐century sedimentation rates were greater than those of previous millennia, with a mid‐century step increase in mean yield from 240 to 425 Mg km?2 yr?1. Annual yields through the twentieth century showed significant positive relations with spring/summer temperature, rainfall, and peak discharge conditions. This finding is significant for the future of sediment transfer at Linnévatnet, and perhaps more broadly in the Arctic, where continued increases in temperature and rainfall are projected. For 2004–2010, annual yields ranged from 294 to 1330 Mg km?2 yr?1. Sediment trap volumes and particle‐size variations indicate that recent annual yields were largely dominated by spring to early summer transfer of relatively coarse‐grained sediment. Fluvial monitoring showed daily to hourly sediment transfer to be related to current and prior discharge, diurnal hysteresis, air temperature, and precipitation. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

11.
Glacier recessions caused by climate change may uncover pro‐glacial lakes that form important sedimentation basins regulating the downstream sediment delivery. The impact of modern pro‐glacial lakes on fluvial sediment transport from three different Norwegian glaciers: Nigardsbreen, Engabreen and Tunsbergdalsbreen, and their long‐term development has been studied. All of these lakes developed in modern times in overdeepened bedrock basins. The recession of Nigardsbreen uncovered a 1.8 km long and on average 15 m deep pro‐glacial lake basin during 1937 to 1968. Since then the glacier front has been situated entirely on land, and the sediment input and output of the lake has been measured. The suspended sediment transport into and out of the lake averaged 11 730 t yr?1 and 2340 t yr?1 respectively. Thus, 20% remained in suspension at the outlet. The measured mean annual bedload supplied to the lake was 11 800 t yr?1, giving a total transport of 23 530 t yr?1 which corresponds to a specific sediment yield of 561 t km?2 yr?1. A 1.9 km long and up to 90 m deep pro‐glacial lake basin downstream from Engabreen glacier was uncovered during 1890 to 1944. The average suspended sediment load delivered from the glacier during the years 1970–1981 amounted to 12 375 t yr?1and the transport out of the lake was 2021 t yr?1, giving an average of 16% remaining in suspension. The mean annual bedload was 8000 t yr?1, thus the total transport was 20 375 t yr?1, giving a specific sediment yield of 566 t km?2 yr?1. For Tunsbergdalsbreen glacier, measurements in the early 1970s indicated that the suspended sediment transport was on average 44 000 t yr?1. From 1987 to 1993 the recession of the glacier uncovered a small pro‐glacial lake, 0.3 km long and around 9 m deep. Downstream from this, the suspended sediment load measured in 2009 was 28 000 t yr?1, indicating that as much as 64% remained in suspension. Flow velocity, grain size of sediment, and morphology of the lake are important factors controlling the sedimentation rate in the pro‐glacial lakes. A survey of the sub‐glacial morphology of Tunsbergdalsbreen revealed that there are several overdeepened basins beneath the glacier. The largest is 4 km long and 100 m deep. When the glacier melts back they will become lakes and act as sedimentation basins. Despite an expected increase in sediment yield from the glacier, little sediment will pass these lakes and downstream sediment delivery will be reduced markedly. Beneath Nigardsbreen there was only a small depression that may form a lake and the sediment delivery will not be significantly affected. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

12.
River deltas are the major repositories of terrestrial sediment flux into the world's oceans. Reduction in riverine inputs into the deltas due to upstream damming might lead to a relative dominance of waves, tides and currents that are especially exacerbated by coastal subsidence and sea‐level rise ultimately affecting the delta environment. Analysis of multi‐date satellite imagery and maps covering the Krishna and Godavari deltas along the east coast of India revealed a net erosion of 76 km2 area along the entire 336‐km‐long twin delta coast during the past 43 years (1965–2008) with a progressively increasing rate from 1·39 km2 yr?1 between 1965 and 1990, to 2·32 km2 yr?1 during 1990–2000 and more or less sustained at 2·25 km2 yr?1 during 2000–2008. At present the Krishna has almost become a closed basin with decreased water discharges into the delta from 61·88 km3 during 1951–1959 to 11·82 km3 by 2000–2008; and the suspended sediment loads from 9 million tons during 1966–1969 to as low as 0·4 million tons by 2000–2005. In the case of the Godavari delta, although the water discharge data do not show any major change, there was almost a three‐fold reduction in its suspended sediment loads from 150·2 million tons during 1970–1979 to 57·2 million tons by 2000–2006. A comparison of data on annual sediment loads recorded along the Krishna and Godavari Rivers showed consistently lower sediment quantities at the locations downstream of dams than at their upstream counterparts. Reports based on bathymetric surveys revealed considerable reduction in the storage capacities of reservoirs behind such dams. Apparently sediment retention at the dams is the main reason for the pronounced coastal erosion along the Krishna and Godavari deltas during the past four decades, which is coeval to the hectic dam construction activity in these river basins. Copyright © 2010 John Wiley and Sons, Ltd.  相似文献   

13.
In this paper, we present a methodology to construct a sediment budget for meso‐scale catchments. We combine extensive field surveys and expert knowledge of the catchment with a sediment delivery model. The meso‐scale Mediterranean drainage basin of the Dragonja (91 km2), southwest Slovenia, was chosen as case study area. During the field surveys, sheet wash was observed on sloping agricultural fields during numerous rainfall events, which was found to be the main source of sediment. With the sediment yield model WATEM/SEDEM the estimated net erosion on the hillslopes 4·1 t ha–1 y–1 (91% of inputs). The second source, bank erosion (4·2%; 0·25 t ha–1 y–1) was monitored during several years with erosion pins and photogrammetric techniques. The last source, channel incision, was derived from geomorphological mapping and lichenomery and provided 3·8% (0·17 t ha–1 y–1) of the sediment input. The river transports its suspended sediment mainly during high‐flow events (sampled with automated water samplers). About 27% (1·2 t ha–1 y–1) of the sediment delivered to the channel is deposited on floodplains and low terraces downstream (estimated with geomorphological mapping, coring and cesium‐137 measurements). The sediment transported as bedload disintegrates during transport to the outlet due to the softness of the bedrock material. As a result, the river carries no bedload when it reaches the sea. The results imply a build‐up of sediment in the valleys catchment. However, extreme flood events may flush large amounts of sediment stored in the lower parts of the system. Geomorphological evidence exists in the catchment that such high magnitude, low frequency events have happened in the past. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

14.
The knowledge of the contribution of sediment sources to river networks is a prerequisite to understand the impact of land use change on sediment yield. We calculated the relative contributions of sediment sources in two paired catchments, one with commercial eucalyptus plantations (0.83 km2) and the other with grassland used for livestock farming (1.10 km2), located in the Brazilian Pampa biome, using different combinations of conventional [geochemical (G), radionuclide (R) and stable isotopes and organic matter properties (S)] and alternative tracer properties [spectrocolorimetric visible-based-colour parameters (V)]. Potential sediment sources evaluated were stream channel, natural grassland and oat pasture fields in the grassland catchment, and stream channel, unpaved roads and eucalyptus plantation in the eucalyptus catchment. The results show that the best combination of tracers to discriminate the potential sources was using GSRV tracers in the grassland catchment, and using GSRV, GSV and GS tracers in the eucalyptus catchment. In all these cases, samples were 100% correctly classified in their respective groups. Considering the best tracers results (GSRV) in both catchments, the sediment source contributions estimated in the catchment with eucalyptus plantations was 63, 30 and 7% for stream channel, eucalyptus stands and unpaved roads, respectively. In the grassland catchment, the source contributions to sediment were 84, 14 and 2% for natural grassland, stream channel and oats pasture fields, respectively. The combination of these source apportionment results with the annual sediment loads monitored during a 3-year period demonstrates that commercial eucalyptus plantations supplied approximately 10 times less sediment (0.1 ton ha−1 year−1) than the traditional land uses in this region, that is, 1.0 ton ha−1 year−1 from grassland and 0.3 ton ha−1 year−1 from oats pasture fields. These results demonstrate the potential of combining conventional and alternative approaches to trace sediment sources originating from different land uses in this region. Furthermore, they show that well-managed forest plantations may be less sensitive to erosion than grassland used for intensive livestock farming, which should be taken into account to promote the sustainable use of land in this region of South America.  相似文献   

15.
A sediment budget for an upland catchment–reservoir system at Burnhope Reservoir, North Pennines, UK has been developed. This provides a framework for quantifying historic and contemporary sediment yields and drainage basin response to disturbance from climate change and human activities in the recent past. Bathymetric survey, core sampling, 137Cs dating and aerial photographs have been used to assess sediment accumulation in the reservoir. The average reservoir sedimentation rate is 1·24 cm yr?1 (annual sediment yield 33·3 t km?2 yr?1 ± 10%, trap efficiency 92%). Mean annual reservoir sedimentation over the 67 year period has been estimated at 592 t ± 10%. Inputs of suspended sediment from direct catchwater streams account for 54% of sediment supply to the budget (best estimate yield of 318 t yr?1 ± 129%), while those from actively eroding reservoir shorelines contribute 328 t yr?1 ± 92%. Sediment yield estimates from stream monitoring and reservoir sedimentation are an order of magnitude lower than those reported from South Pennine reservoirs of comparable drainage basin area. Analysis of historical rainfall series for the catchment shows fluctuations in winter and summer rainfall patterns over the past 62 years. From 1976 to 1998 there has been a diverging trend between winter and summer rainfall, with a large increase in winter and a gradual decrease in summer totals. Periods of maximum variation occur during the summer drought events of the late 1970s, early 1980s and mid‐1990s. Analysis of the particle size of core sediments highlights abrupt increases in sand‐sized particles in the top 20 cm of the core. Based on the 137Cs chronology, these layers were deposited from the late 1970s onwards and relate to these diverging rainfall records and rapidly fluctuating reservoir levels. This provides evidence of potential sediment reworking within the reservoir by rapid water‐level rise after drought. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

16.
Event sediment transport and yield were studied for 45 events in the upstream part of the 260 km2 agricultural Koga catchment that drains to an irrigation reservoir. Discharge and turbidity data were collected over a period of more than a year, accompanied by grab sampling. Turbidity was very well correlated with the sediment concentrations from the samples (r = 0.99), which allowed us to estimate the temporal patterns of sediment concentrations within events. The hysteresis patterns between discharge and sediment concentrations were analysed to provide insight into the different sediment sources. Anticlockwise patterns are the dominant hysteresis patterns in the area, suggesting smaller contributions of suspended sediment from the river channels than from the hillslopes and agricultural areas. Complicated types of hysteresis patterns were mostly observed for long events with multiple peaks. For a given discharge, sediment yields in August and September, when the catchment was almost completely covered with vegetation, were much smaller than during the rest of the rainy season. The hysteresis patterns and timing suggest that the sediment availability from the agricultural areas and hillslopes affects sediment yields more strongly than does peak discharge. Two distinct types of sediment rating curves were observed for the season when the agricultural land was covered with vegetation and when it was not, indicating the dominating contribution of land use/cover to sediment yields in the catchment. The rate of suspended sediment transport in the area was estimated as 25.6 t year?1 ha?1. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

17.
Abstract

Rainfall–runoff induced soil erosion causes important environmental degradation by reducing soil fertility and impacting on water availability as a consequence of sediment deposition in surface reservoirs used for water supply, particularly in semi-arid areas. However, erosion models developed on experimental plots cannot be directly applied to estimate sediment yield at the catchment scale, since sediment redistribution is also controlled by the transport conditions along the landscape. In particular, representation of landscape connectivity relating to sediment transfer from upslope areas to the river network is required. In this study, the WASA-SED model is used to assess the spatial and temporal patterns of water and sediment connectivity for a semi-arid meso-scale catchment (933 km2) in Brazil. It is shown how spatial and temporal patterns of sediment connectivity within the catchment change as a function of landscape and event characteristics. This explains the nonlinear catchment response in terms of sediment yield at the outlet.

Citation Medeiros, P. H. A., Güntner, A., Francke, T., Mamede, G. L. & de Araújo, J. C. (2010) Modelling spatio-temporal patterns of sediment yield and connectivity in a semi-arid catchment with the WASA-SED model. Hydrol. Sci. J. 55(4), 636–648.  相似文献   

18.
《Journal of Hydrology》2006,316(1-4):213-232
The Magdalena River, a major fluvial system draining most of the Colombian Andes, has the highest sediment yield of any medium-sized or large river in South America. We examined sediment yield and its response to control variables in the Magdalena drainage basin based on a multi-year dataset of sediment loads from 32 tributary catchments. Various morphometric, hydrologic, and climatic variables were estimated in order to understand and predict the variation in sediment yield. Sediment yield varies from 128 to 2200 t km−2 yr−1 for catchments ranging from 320 to 59,600 km2. The mean sediment yield for 32 sub-basins within the Magdalena basin is ∼690 t km−2 yr−1. Mean annual runoff is the dominant control and explains 51% of the observed variance in sediment yield. A multiple regression model, including two control variables, runoff and maximum water discharge, explains 58% of the variance. This model is efficient (ME=0.89) and is a valuable tool for predicting total sediment yield from tributary catchments in the Magdalena basin. Multiple correlations for those basins corresponding to the upper Magdalena, middle basin, Eastern Cordillera, and catchment areas greater than 2000 km2, explain 75, 77, 89, and 78% of the variance in sediment yield, respectively. Although more variance is explained when dataset are grouped into categories, the models are less efficient (ME<0.72). Within the spatially distributed models, six catchment variables predict sediment yield, including runoff, precipitation, precipitation peakedness, mean elevation, mean water discharge, and relief. These estimators are related to the relative importance of climate and weathering, hillslope erosion, and fluvial transport processes. Time series analysis indicates that significant increases in sediment load have occurred over 68% of the catchment area, while 31% have experienced a decreasing trend in sediment load and thus yield. Land use analysis and increasing sediment load trends indicate that erosion within the catchment has increased over the last 10–20 years.  相似文献   

19.
《水文科学杂志》2013,58(6):899-915
Abstract

The results are described of 16 years operation of a measuring station for the automatic recording of water discharge, bed load and suspended sediment transport in the Rio Cordon catchment, a small alpine basin (5 km2) located in northeastern Italy. Hillslope erosion processes were investigated by surveying individual sediment sources repeatedly. Annual and seasonal variations of suspended sediment load during the period 1986–2001 are analysed along with their contribution to the total sediment yield. The results show that suspended load accounted for 76% of total load and that most of the suspended sediment transport occurred during two flood events: an extreme summer flash flood in September 1994 (27% of the 16-years total suspended load) and a snowmelt-induced event in May 2001 accompanied by a mud flow which fed the stream with sediments. The role of active sediment source areas is discussed in relation to the changes in flood peak—suspended load trends which became apparent after both the 1994 and the 2001 events.  相似文献   

20.
An important gap in the management of land erosion in mining-affected areas is the understanding of the entire sediment routing system and the links between sources and storage at the catchment scale. In this study, we examine sediment delivery and its seasonality in the nickel mining-affected Santa Cruz and Pamalabawan catchments in the Philippines. We monitored discharge, suspended sediment concentrations and suspended sediment loads across 13 sub-catchments with contrasting degrees of mining influence from June 2018 to July 2019. First, we show the importance of the size of the area that has been physically disturbed within our sub-catchments, with as little as 10–22% of relative disturbance area being enough to generate four-fold to eight-fold increase in the sediment yield relative to less disturbed and pristine areas. We found that sub-catchments with > 10% disturbance exhibit the highest sediment yields (15.5 ± 44.7 t km−2 d−1) compared with sub-catchments with < 10% disturbance (3.6 ± 17.7 t km−2 d−1) and undisturbed catchments (2.0 ± 5.7 t km−2 d−1). We also show that sediment flushing predominantly occurs in the most disturbed sub-catchments at the onset of the wet season. A small number of flood events transports the bulk of the sediment, with hysteresis effects being most pronounced in disturbed areas. Lastly, we show that floodplain sediment recycling exerts a key control on sediment delivery at both reach and catchment scales, with the relative contribution of floodplain sources to the sediment budget becoming dominant in the latter stages of the wet season- up to 89% of the total sediment export per storm event. This study highlights the importance of both degree of disturbance and sediment pathways in controlling sediment transport in mining-disturbed areas, and that considering the entire sediment routing system including intermediate stores is crucial to optimizing existing and future measures against siltation and potential contamination of trace metals and metalloids downstream of mining areas.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号