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1.
A hydrologic regression sediment-yield model was established to determine the relationship between water discharge and suspended sediment discharge at the Blue Nile and the Atbara River outlet stations during the flood season. The model consisted of two main submodels: (1) a suspended sediment discharge model, which was used to determine suspended sediment discharge for each basin outlet; and (2) a sediment rating model, which related water discharge and suspended sediment discharge for each outlet station. Due to the absence of suspended sediment concentration measurements at or near the outlet stations, a minimum norm solution, which is based on the minimization of the unknowns rather than the residuals, was used to determine the suspended sediment discharges at the stations. In addition, the sediment rating submodel was regressed by using an observation equations procedure. Verification analyses on the model were carried out and the mean percentage errors were found to be +12.59 and –12.39, respectively, for the Blue Nile and Atbara. The hydrologic regression model was found to be most sensitive to the relative weight matrix, moderately sensitive to the mean water discharge ratio, and slightly sensitive to the concentration variation along the River Nile's course.  相似文献   

2.
Riverine sediment load, a reflection of basin erosion and sediment yield, is influenced by both climatic and human factors. Complex interaction between various factors within a basin dampens and counteracts the forces that drive sediment variations. The gross human impact index and the index estimation method have both been proposed to reflect the impacts of human activities on soil erosion and sediment yield. Sediment load and daily rainfall data from 1955 to 2010 in the upper Yangtze basin, and in the Wu, Jialing, Min and Jinsha subbasins, were collected to assess the human versus climatic impacts on sediment yield. From 1955 to 2010, the average annual runoff in the study area was 428.2 billion m3, and the average annual suspended sediment load was approximately 0.43 billion t. There was a critical point in 1984, 1985, 1991, 1993 and 1999 when the sediment load decreased in the Wu, Jialing, upper Yangtze, Min and Jinsha river, respectively. The annual regional rainfall erosivities in the upper Yangtze basin in most years ranged between 2,500 and 3,500 MJ mm hm?2 h?1 year?1 and fluctuated around 3,000 MJ mm hm?2 h?1 year?1 with a small coefficient of variation of 0.11. In the Jinsha subbasin, the index indicated that increasing rainfall erosivity could not account for the reduction in riverine sediment load and that anthropogenic erosion-control measures played a key role. The index values for the Min, Jialing and Wu subbasins ranged from 76 to 97 % and for the upper Yangtze basin is 95 %, demonstrating the joint effects of precipitation and human activities in all basins, with erosion-controlling measures playing a major role in sediment load reduction.  相似文献   

3.
通过2013年6-9月对唐古拉山冬克玛底冰川流域河水的逐日定时样品采集,并结合流域水文与气象资料,对径流的总溶解固体（TDS）和悬移质的变化特征进行分析。结果表明：2013年消融期的平均气温为3.7℃,消融期降水量为546 mm,7月和8月两个月径流量占消融期总径流量的63%。消融期逐日的TDS变化范围为31~140 mg·L-1,平均值为60 mg·L-1,TDS随径流变化显著,表现为消融强烈时（7-8月） TDS浓度较低,消融初期（6月）和末期（9月）时TDS浓度较高;径流中TDS与悬移质浓度（SSC）变化表现出相反变化趋势,即消融强烈时悬移质浓度较高,而消融初期与末期悬移质浓度较低,消融期平均悬移质浓度为122.8 mg·L-1,流量-SSC时序关系表现为以顺时针滞后事件为主。2013年冬克玛底冰川流域消融期的化学侵蚀总量和物理侵蚀总量分别为2.214×103 t和6.722×103 t,化学侵蚀与物理侵蚀率的比值为0.33。  相似文献   

4.
Small rivers draining high-rainfall basins and mountainous terrain west of the Cordilleras in South America have disproportionately high water discharge and sediment load. Fifteen rivers in western Colombia discharge a combined 254 km3 yr-1 or 8020 m3 s-1 of water into the Pacific. Sediment yield is strongly correlated with basin area (R2=0.97), and sediment load is correlated with water discharge (R2=0.73). Rio San Juan occupies a 16,465-km2 basin with a mean annual rainfall of 7277 mm. It has the highest water discharge (2550 m3 s-1), sediment load (16x106 t yr-1), and basin-wide sediment yield (1150 t km-2 yr-1) on the entire west coast of South America. Rio Patía drains a 23,700-km2 basin with a mean annual rainfall of 2821 mm. Its water discharge, sediment load, and basin-wide sediment yield are 1291 m3 s-1, 14 t yr-1, and 972 t km-2 yr-1, respectively. Rio San Juan and Rio Patía deliver 30x106 t of suspended sediment annually into the Pacific. Analysis of data for an additional 22 rivers in Colombia that drain into the Caribbean Sea indicates that the Pacific rivers have at least twice the sediment yield compared with the larger Rio Magdalena. Our results confirm that the Pacific rivers of Colombia need to be accounted for in global sediment budgets.  相似文献   

5.
Massive construction on the Drava River basin and on the river itself during the last centuries, as well as recent climate change and/or variability, has caused many different and possibly dangerous changes to its hydrological and ecological regime. Since 1975, numerous hydrotechnical works have been carried out on the 60-km long section of the Drava River from the Slovenian–Croatian border to the River Mura mouth. Three hydrotechnical power plants with three reservoirs and three long inlet and outlet canals have been built. Changes in water level, discharge and suspended sediment yield along the Drava River measured in Croatia, downstream of the three Croatian reservoirs, during the last 30–130 years are presented. The investigation focuses on changes that have occurred during the last thirty-odd years, caused by the anthropogenic influences on the Drava River watercourse and its catchment in Croatia and Hungary, and probably by climate change or variability. Methods of rescaled adjusted partial sums, statistical tests, as well as regression and correlation analyses are used to explain changes in water level, discharge and suspended sediment yield. There is evidence in the time series of decreases in the minimum, mean and maximum annual water levels, and minimum and mean discharges on the lower part of the Drava River. One of the main objectives of this study was to examine the effect of dams and reservoirs operation on the changes in the downstream suspended sediment regime. The amount of suspended sediment has been greatly reduced, which can cause serious consequences.  相似文献   

6.
Erosion and sediment redistribution are important processes in landscape changes in the short and long term. In this study, the RMMF model of soil erosion and the SEDD model of sediment delivery were used to estimate annual soil loss and sediment yield in an ungauged catchment of the Spanish Pre-Pyrenees and results were interpreted in the context of the geomorphic features. The Estaña Catchment is divided into 15 endorheic sub-catchments and there are 17 dolines. Gullies and slopes were the main erosive geomorphic elements, whereas the colluvial, alluvial, valley floor, and doline deposits were depositional elements. Spatially distributed maps of gross soil erosion, sediment delivery ratio (SDR), and sediment yield (SY) were generated in a GIS. Severe erosion rates (>100 Mg ha?1 year?1) were found in gullies, whereas mean and maximum erosion rates were very high on slopes developed on Keüper Facies and high in soils on Muschelkalk Facies. Where crops are grown, the depositional-type geoforms were predicted by the models to have an erosive dynamic. Those results were consistent with the rates of erosion quantified by 137Cs which reflects the significant role of human activities in triggering soil erosion. Catchment area was positively correlated with erosion rate, but negatively correlated with SDR and SY. The latter were negatively correlated with the proportion of the surface catchment covered with forests and scrublands. The topography of the area influenced the high SDR and SY in the dolines and valley floors near the sinks. Intra-basin stored sediment was 59.2% of the total annual eroded soil in the catchment. The combination of the RMMF and SEDD models was an appropriate means of assessing the effects of land uses on soil erosion and obtaining a better understanding of the processes that underlie the geomorphic changes occurring in mountainous environments of the Mediterranean region.  相似文献   

7.
This paper examines the credibility and predictability of sediment flux of the Changjiang River that has discharged into the seas on the basis of historical database. The assumption of the study stands on the lack of sufficient observation data of suspended sediment concentration (SSC) during peaking flood period, which most likely results in the application of an inappropriate method to the downstream-most Datong hydrological gauging station in the Changjiang basin. This insufficient method (only 30–50 times of SSC observation per year), that obviously did not cover the peaking SSC during peaking floods, would lead to an inaccuracy in estimating the Changjiang sediment load by 4.7×108 t/a (multiyearly) into the seas. Also, sediment depletion that often takes place upstream of the Changjiang basin has, to some extent, lowered the credibility of traditional sediment rating curve that has been used for estimating sediment budget. A newly-established sediment rating curve of the present study is proposed to simulate the sediment flux/load into the seas by using those SSC only under discharge of 60000 m3/s at the Datong station-the threshold to significantly correlate to SSC. Since discharge of 60000–80000 m3/s is often linked to extreme flood events and associated sediment depletion in the basin, unincorporating SSC of 60000–80000 m3/s into the sediment rating curve will increase the credibility for sediment load estimation. Using this approach of the present study would indicate the sediment load of 3.3×108–6.6×108 t/a to the seas in the past decades. Also, our analytical result shows a lower sediment flux pattern in the 1950 s, but higher pattern in the 1960 s–1980 s, reflecting the changes in landuse in the upstream of Changjiang basin, including widely devastated deforestation during the middle 20th century.  相似文献   

8.
Water discharge from the Patuxent River into its estuary was near-average (95%) during the water year 1968–1969 although precipitation was only 79% of the average. Suspended-sediment discharge into the estuary, however, was more then double the normal yield (344 metric tons/km2 compared to 143 metric tons/km2). These increases in runoff and suspended-sediment yields, despite decreased precipitation, must be attributed to urbanization of the drainage basin.The maximum measured suspended-sediment concentrations in the rural Middle Patuxent basin (Piedmont Province) increased only 40-fold during an increase from “average” to high water runoff (15 mg/l to 600 mg/l). In the portion of the Little Patuxent River basin undergoing urbanization (Piedmont portion), stream concentrations increased by over two orders of magnitude (20 mg/l to 2400 mg/l) as a result of heavy rainfall. The area undergoing urbanization of the Little Patuxent yielded more than twice as much suspended sediment per unit area as the rural Middle Patuxent (620 metric tons/km2 versus 290 metric tons/km2). This increase also is interpreted to be the direct result of erosion of soils denuded or disturbed during urban construction.Using the Middle Patuxent as a “standard” for normal erosion rates in rural areas, construction sites contributed about 82% of the suspended sediment discharged by the Patuxent River into its estuary even though such sites represented only 23% of the drainage basin.  相似文献   

9.
Suspended sediment concentration is a major variable influencing soil erosion and loss, study on which at different spatial scales is of great meaning to understand soil erosion mechanism and sediment transport process. Based on data from 4 sloping surfaces and 7 basins ranging from 0.0003 to 187 km2 in area, the suspended sediment concentration in flood season (SSC) with drainage area is studied. With increasing drainage area on the slope surfaces, the mean suspended sediment concentration in flood season (MSSC) enhances continuously until a peak value of 685 kg m−3 occurs at the whole slope surface No. 7 runoff plot resulting from harder and harder erosion forms downslope. Entering basin systems, the diluted action of subsurface water on the toeslope on MSSC and small water flow power Ω make a minimum MSSC value of 568 kg m−3 occur in the first-order basin system Tuanshangou basin at an area of 0.18 km2, and then from Tuanshangou basin to larger basins, the positive feedback function among drainage density, water flow energy, and hyperconcentrated flow as well as its reduction of settling velocity of coarser particles generates continuously increasing MSSC with drainage area.  相似文献   

10.
In this study, a Physiographic Soil Erosion–Deposition Model (PSED) is applied for better management of a watershed. The PSED model can effectively evaluate the key parameters of watershed management: surface runoff discharge, suspended sediment transport rate, quantity of soil erosion, and spatial distribution of soil erosion and deposition. A basin usually contains multiple watersheds. These watersheds may have complex topography and heterogeneous physiographic properties. The PSED model, containing a physiographic rainfall-runoff model and a basin scale erosion–deposition model, can simulate the physical mechanism of the entire erosion process based on a detailed calculation of bed-load transportation, surface soil entrainment, and the deposition mechanism. With the assistance of Geographic Information Systems (GIS), the PSED model can handle and analyze extremely large hydrologic and physiographic datasets and simulate the physical erosion process without the need for simplification. We verified the PSED model using three typhoon events and 40 rainfall events. The application of PSED to Chou-Shui River basin shows that the PSED model can accurately estimate discharge hydrographs, suspended sediment transport rates, and sediment yield. Additionally, we obtained reasonable quantities of soil erosion as well as the spatial distribution of soil erosion and deposition. The results show that the PSED model is capable of calculating spatially distributed soil erosion and suspended sediment transport rates for a basin with multiple watersheds even if these watersheds have complex topography and heterogeneous physiographic properties.  相似文献   

11.
Environmental geochemistry of Damodar River basin, east coast of India   总被引：1，自引：0，他引：1  
 Water and bed sediment samples collected from the Damodar River and its tributaries were analysed to study elemental chemistry and suspended load characteristics of the river basin. Na and Ca are the dominant cations and HCO3 is the dominant anion. The water chemistry of the Damodar River basin strongly reflects the dominance of continental weathering aided by atmospheric and anthropogenic activities in the catchment area. High concentrations of SO4 and PO4 at some sites indicate the mining and anthropogenic impact on water quality. The high concentration of dissolved silica, relatively high (Na+K)/TZ+ ratio (0.2–0.4) and low equivalent ratio of (Ca+Mg)/(Na+K) indicate that dissolved ions contribute significantly to the weathering of aluminosilicate minerals of crystalline rocks. The seasonal data show a minimum ionic concentration in the monsoon season, reflecting the influence of atmospheric precipitation on total dissolved solids contents. The suspended sediments show a positive correlation with discharge and both discharge and suspended load reach their maximum value during the monsoon season. Kaolinite is the mineral that is possibly in equilibrium with the water. This implies that the chemistry of the Damodar River water favours kaolinite formation. The concentration of heavy metals in the finer size fraction (<37 μ m) is significantly higher than the bulk composition. The geoaccumulation index values calculated for Fe, Mn, Zn, Ni and Cr are well below zero, suggesting that there is no pollution from these metals in Damodar River sediments. Received: 21 January 1998 · Accepted: 4 May 1998  相似文献   

12.
In Jakarta, climate change has been detected through rising air temperatures, increased intensity of rainfall in the wet season, and sea level rise. The coupling of such changes with local anthropogenic driven modifications in the environmental setting could contribute to an increased probability of flooding, due to increase in both extreme river discharge and sedimentation (as a result of erosion in the watersheds above Jakarta and as indicated by sediment yield in the downstream area). In order to respond to the observed and projected changes in river discharge and sediment yield, and their secondary impacts, adaptation strategies are required. A possible adaptation strategy is through policy making in the field of spatial planning. For example, in Indonesia, presidential regulation number 54 year 2008 (Peraturan Presiden Nomor 54 Tahun 2008—Perpres 54/2008) was issued as a reference for the implementation of water and soil conservation. This paper assesses the impact of climate and land cover change on river discharge and sediment yield, as well as the effects of Perpres 54/2008 on that river discharge and sediment yield. The spatial water balance model Spatial Tools for River Basins and Environmental and Analysis of Management Option was used for the runoff computations, whilst the Spatial Decision Assistance of Watershed Sedimentation model was used to simulate erosion, Sediment Delivery Ratio, and sediment yield. The computation period is from January 1901 to December 2005, at the scale of the following watersheds: Ciujung, Cisadane, Ciliwung, and Citarum. During the twentieth century, computed average discharge in the downstream area (near Jakarta) increased between 2.5 and 35 m3/s/month, and sediment yield increased between 1 × 103 and 42 × 103 tons/year. These changes were caused by changes in both land cover and climate, with the former playing a stronger role. Based on a computation under a theoretical full implementation of the spatial plan proposed by Perpres 54/2008, river discharge would decrease by up to 5 % in the Ciliwung watershed and 26 % in the Cisadane watershed. The implementation of Perpres 54/2008 could also decrease the sediment yield, by up to 61 and 22 % in the Ciliwung and Cisadane watersheds, respectively. These findings show that the implementation of the spatial plan of Perpres 54/2008 could significantly improve watershed response to runoff and erosion. This study may serve as a tool for assessing the reduction in climate change impacts and evaluating the role of spatial planning for adaptation strategies.  相似文献   

13.
“泾渭分明”的现代特点分析   总被引：4，自引：0，他引：4  
清浊变化是指常年及汛期的含沙量及输沙量变化。泾河年均径流量仅为渭河的1/2倍(资料截止1997),输沙量却为渭河的2.35倍,含沙量为渭河的4.57倍。现在是泾浊渭清。输沙量与最大流量间为正相关关系,相关系数渭河为0.7516,泾河为0.8279。输沙量季节集中的程度更大,最大月输沙量占年输沙量的71.23%,最大月径流量占年径流量的39.22%。渭河较小的输沙量在于气候干旱导致的径流量减小。泾河较大的输沙量在于泾河流域现代人为活动对生态系统破坏更为严重。  相似文献   

14.
三峡大坝建成后长江输沙量的减少及其对长江三角洲的影响   总被引：19，自引：6，他引：13  
三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×108～2.5×108t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×108～2.28×108t。二者的数值相当接近,然而与近50年的观测(4.33×108t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。  相似文献   

15.
三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×108～2.5×108t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×108～2.28×108t。二者的数值相当接近,然而与近50年的观测(4.33×108t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。  相似文献   

16.
对于雨洪河流,河流年输沙量主要来源于1场或几场高强度暴雨洪水过程,开展流域次洪输沙规律研究对认识流域水沙变化特性、提升流域产输沙的预测能力具有重要意义。利用嘉陵江流域小河坝站、罗渡溪站、武胜站及北碚站的历年场次洪量与输沙量资料,基于径流侵蚀功率理论和M-K分析等方法,系统分析了嘉陵江不同区域的次洪输沙特性。结果表明:嘉陵江流域汛期洪量和输沙量主要来自于嘉陵江干流;嘉陵江不同区域场次洪量均呈不显著减少趋势,次洪输沙模数（输沙量）总体呈显著减少趋势,但小河坝站2013—2020年次洪输沙模数（输沙量）呈显著增加趋势;随着径流侵蚀功率的逐渐增加,各区域不同时段的次洪输沙模数（输沙量）的变幅逐渐减小;嘉陵江干流区武胜站场次洪水输沙过程受人类活动影响最大、渠江罗渡溪站次之、涪江小河坝站最小;受汶川地震及强降雨等影响,小河坝站和北碚站2013—2020年次洪输沙量较1999—2012年有一定程度增加,但北碚站增幅小于小河坝站。  相似文献   

17.
The USA Clean Water Act requires the development of a total maximum daily load (TMDL) when Minnesota’s water quality standard for turbidity is exceeded; however, regions underlain with fine-grained lacustrine deposits yield large natural background loads of suspended inorganic sediment. A review of hydrogeologic pathways was conducted along with the statistical analysis of geomorphic metrics, collected at 15 sites with varying drainage areas in the upper Nemadji River basin, northeastern Minnesota. Regression analysis indicated a strong linkage between bankfull cross-sectional area and drainage area. Dimensionless geomorphic metric ratios were developed to predict channel evolution potential and associated channel erosion risk. Sites located in drainage areas less than 2 km2 had low erosion risk and showed a correlation between channel slope and relative roughness (D 84/mean bankfull channel depth, 88%). A principal components analysis explained over 98% of the variance between sites and indicated five important channel shape metrics to predict channel erosion: bankfull width, bankfull depth, maximum depth, cross-sectional area, and valley beltwidth. Mass wasting of cohesive stream channel sediment was influenced by groundwater discharge and produced turbid waters in the upper Nemadji River.  相似文献   

18.
This study investigated the prediction of suspended sediment load in a gauging station in the USA by neuro-fuzzy, conjunction of wavelet analysis and neuro-fuzzy as well as conventional sediment rating curve models. In the proposed wavelet analysis and neuro-fuzzy model, observed time series of river discharge and suspended sediment load were decomposed at different scales by wavelet analysis. Then, total effective time series of discharge and suspended sediment load were imposed as inputs to the neuro-fuzzy model for prediction of suspended sediment load in one day ahead. Results showed that the wavelet analysis and neuro-fuzzy model performance was better in prediction rather than the neuro-fuzzy and sediment rating curve models. The wavelet analysis and neuro-fuzzy model produced reasonable predictions for the extreme values. Furthermore, the cumulative suspended sediment load estimated by this technique was closer to the actual data than the others one. Also, the model could be employed to simulate hysteresis phenomenon, while sediment rating curve method is incapable in this event.  相似文献   

19.
Hilda Glacier, a small cirque glacier in the Canadian Rocky Mountains, yields two principal types of sediment: ablation till, deficient in fine material and produced by rockfalls and avalanches falling on to the glacier surface, and basal lodgement till, rich in fines and formed mainly by subglacial erosion. Recent recession from its Neoglacial maximum has exposed large areas of basal till with thin veneers of ablation till which, when combined with present subglacial and supraglacial debris, provide abundant material for erosion and transport by the mcltwatcr stream. Sediment transport measurements over two summers (1977–1978) showed that bed load and suspended load occur in approximately equal proportions and that dissolved loads are minor. Local source variations, especially bank slumps, are a major cause of scatter in sediment rating curves. Suspended-sediment concentrations are greater early in the melt season due to availability of loose sediment produced by freezing and thawing. Other contributors to scatter in suspended-sediment rating curves include rain showers and diurnal hysteretic effects. Although the distinction between bed load and suspended load is never sharp, available data suggest that the sand/ gravel grain-size boundary (-1ø) approximates the suspendcd-load/bed-load division for characteristic Hilda flows transporting gravel. This approximation, combined with till grain-size analyses, suspended-sediment measurements, and spatial distributions of till types, leads to the following computations of fluvial sediment sources: for suspended load - 6% supraglacial, 47% subglacial, 47% channel banks; for bed load - 46% supraglacial, 27% each subglacial and channel banks. Supraglacial debris provides only about one-fourth of all fluvial sediment, but nearly half of the bed load.  相似文献   

20.
Erosion potential method (EPM) and Modified Pacific Southwest Interagency Committee (MPSIAC) are two empirical models for estimating soil erosion and sediment delivery. These models use a relatively simple formulation, but they are still applied in various areas with different environmental conditions. However, evaluation of their efficiency is challenging. Accordingly, the main purpose of this study is investigating the performance of EPM and MPSIAC in estimating soil erosion and sediment yield using sediment rating curve (SRC) methods. Talar watershed in Iran was selected as the study area and suspended sediment load (SSL) of two Shirgah–Talar and Valikbon stations were used to assess the output of the models. Remote sensing and geographic information system were utilized in implementing the models. The estimated sediment yield values by the models were evaluated using the results of least square error regression and quantile regression (QR) SRC methods. Then, sediment yield values were obtained from 20-year discharge data (1992–2011). Despite the high uncertainty of QR results, the annual sediment delivery values of the models were achieved in an acceptable range. The most likely (with a probability of 0.5) average annual SSL values were between 713?×?103 and 840?×?103 ton for Shirgah–Talar station. Those values for Valikbon station were between 3142?×?101 and 3702?×?101. Moreover, the estimated average sediment yield in Shirgah–Talar station using MPSIAC and EPM were 591392 and 514054 ton/year, respectively. Those values for Valikbon station were 51881 and 27449 ton/year. Then, the results proved the better performance of MPSIAC in estimating SSL in the study area compared with EPM.  相似文献   

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