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1.
This paper presents an assessment of the Soil and Water Assessment Tool(SWAT) on a glaciated(Qugaqie) and a non-glaciated(Niyaqu) subbasin of the Nam Co Lake. The Nam Co Lake is located in the southern Tibetan Plateau, two subbasins having catchment areas of 59 km~2 and 388 km~2, respectively. The scores of examined evaluation indices(i.e., R~2, NSE, and PBIAS) established that the performance of the SWAT model was better on the monthly scale compared to the daily scale. The respective monthly values of R~2, NSE, and PBIAS were 0.94, 0.97, and 0.50 for the calibration period while 0.92, 0.88, and -8.80 for the validation period. Glacier melt contribution in the study domain was simulated by using the SWAT model in conjunction with the Degree Day Melt(DDM) approach. The conjunction of DDM with the SWAT Model ensued improved results during both calibration(R~2=0.96, NSE=0.95, and PBIAS=-13.49) and validation (R~2=0.97, NSE=0.96, and PBIAS=-2.87) periods on the monthly time scale. Average contribution(in percentage) of water balance components to the total streamflow of Niyaqu and Qugaqie subbasins was evaluated. We found that the major portion(99.45%) of the streamflow in the Niyaqu subbasin was generated by snowmelt or rainfall surface runoff(SURF_Q), followed by groundwater(GW_Q, 0.47%), and lateral(LAT_Q, 0.06%) flows. Conversely, in the Qugaqie subbasin, major contributor to the streamflow(79.63%) was glacier melt(GLC_Q), followed by SURF_Q(20.14%), GW_Q(0.13%), and LAT_Q(0.089%). The contribution of GLC_Q was the highest(86.79%) in July and lowest(69.95%) in September. This study concludes that the performance of the SWAT model in glaciated catchment is weak without considering glacier component in modeling; however, it performs reasonably well in non-glaciated catchment. Furthermore, the temperature index approach with elevation bands is viable in those catchments where streamflows are driven by snowmelt. Therefore, it is recommended to use the SWAT Model in conjunction with DDM or energy base model to simulate the glacier melt contribution to the total streamflow. This study might be helpful in quantification and better management of water resources in data scarce glaciated regions.  相似文献   

2.
Application of swat model in the upstream watershed of the Luohe River   总被引：6，自引：0，他引：6  
1INTRODUCTIONIntheHuanghe(Yellow) Riverbasin, soilerosionisaseriousproblem,whilerunoffandsedimentyieldsim-ulation hasnotbeenextensivelystudiedonthebasisofGIS(GeographicInformationSystem) and dis-tributedhydrologicalmodel.Inthisstudy,theLushiwatershed,whichislocatedattheupstreamoftheLushiHydrologicalStationintheLuoheRiver—thebiggesttributary oftheHuanghe Riveranddown-streamofXiaolangdiDam,isselectedasthestudyarea.ThelevelofsoilerosioninLushiwatershedismoderatein theHuangheRiverbas…  相似文献   

3.
淮河流域是水体遭受营养盐污染较严重的地区,本研究选择淮河上游的淮滨流域（淮滨站以上,流域面积1.6万km2）为研究对象,首先构建了淮滨流域SWAT水文水质模型,然后利用2011—2017年淮滨站实测的月径流和月氨氮浓度对SWAT模型进行了校正与验证,最后基于全球气候模型（GCM）气象数据,预测了未来30年（2020—2029年、2030—2039年、2040—2049年）不同气候变化情境（RCP2.6、RCP4.5、RCP6.0、RCP8.5）下的径流、氨氮浓度和非点源总氮负荷。结果发现,径流在校正期和验证期的Nash-Suttcliffe系数均为0.79,氨氮在校正期和验证期的Nash-Suttcliffe系数均高于0.5,表明模型的适用性良好。研究发现本研究区施肥量与土地利用类型是非点源氮负荷空间分异的主导因素。2020—2049年,不同气候变化情景下,本研究区的降水量和气温均为增长趋势。假如保持基准期（2011—2016年）污染排放强度,仅考虑气候变化影响,流域内非点源污染总氮负荷将比基准期最多增加31.8%,流域出水口淮滨站的年均氨氮浓度将最多减小42.6%。本研究可以为气候变化下淮滨流域的水文水质管理提供科学支撑。  相似文献   

4.
黑河山区流域平均坡长的计算与径流模拟   总被引：1，自引：0，他引：1  
 流域平均坡长是侧向流和汇流时间计算的重要参数,其会影响地表径流的计算。应用SWAT 2005和ArcView GIS 3.2集成的AVSWAT模型,对黑河干流上游山区流域莺落峡出山口径流进行模拟,发现其计算的流域平均坡长存在较大误差,进而影响到模拟结果。利用子流域内已知的平均坡度和平均坡长建立回归方程,计算各子流域的平均坡长,替换AVSWAT计算的不合理值,在保持其他参数不变的情况下,模拟的月径流纳什系数从0.60提高到0.75,模拟结果得到显著提高。敏感性分析结果和径流曲线数(CN2)的分析也间接验证了流域平均坡长修正方法的可行性。在修正流域平均坡长后,对AVSWAT模型的其他参数CN2等进行优化,模拟的月径流的纳什系数达到0.81,表明本文建议的流域平均坡长计算方法是可以应用到实际的干旱区黑河流域并取得较好模拟效果。  相似文献   

5.
The Loess Plateau of China has experienced a lengthy drought and severe soil erosion.Changes in precipitation and land use largely determine the dynamics of runoff and sediment yield in this region. Trend and mutation analyses were performed on hydrological data(1981–2012) from the Yanwachuan watershed in the Loess Plateau Gully Region to study the evolution characteristics of runoff and sediment yield. A time-series contrasting method also was used to evaluate the effects of precipitation and soil and water conservation(SWC) on runoff and sediment yield. Annual sediment yield declined markedly from 1981 to 2012 although there was no significant change in annual precipitation and annual runoff. Change points of annual runoff and annual sediment yield occurred in 1996 and 1997,respectively. Compared with that in the baseline period(1981–1996), annual runoff and annual sediment yield in the change period(1997–2012)decreased by 17.0% and 76.0%, respectively, but annual precipitation increased by 6.3%. Runoff decreased in the flood season and normal season, but increased in the dry season, while sediment yield significantly declined in the whole study period. The SWC measures contributed significantly to the reduction of annual runoff(137.9%) and annual sediment yield(135%) and were more important than precipitation. Biological measures(forestland and grassland) accounted for 61.04% of total runoff reduction, while engineering measures(terraces and dams) accounted for 102.84% of total sediment yield reduction. Furthermore, SWC measures had positive ecological effects. This study provides a scientific basis for soil erosion control on the Loess Plateau.  相似文献   

6.
Hydrologiska Byrans Vattenbalansavdeling(HBV) Light model was used to evaluate the performance of the model in response to climate change in the snowy and glaciated catchment area of Hunza River Basin. The study aimed to understand the temporal variation of streamflow of Hunza River and its contribution to Indus River System(IRS). HBV model performed fairly well both during calibration(R2=0.87, Reff=0.85, PBIAS=-0.36) and validation(R2=0.86, Reff=0.83, PBIAS=-13.58) periods on daily time scale in the Hunza River Basin. Model performed better on monthly time scale with slightly underestimated low flows period during bothcalibration(R2=0.94, Reff=0.88, PBIAS=0.47) and validation(R2=0.92, Reff=0.85, PBIAS=15.83) periods. Simulated streamflow analysis from 1995-2010 unveiled that the average percentage contribution of snow, rain and glacier melt to the streamflow of Hunza River is about 16.5%, 19.4% and 64% respectively. In addition, the HBV-Light model performance was also evaluated for prediction of future streamflow in the Hunza River using future projected data of three General Circulation Model(GCMs) i.e. BCC-CSM1.1, CanESM2, and MIROCESM under RCP2.6, 4.5 and 8.5 and predictions were made over three time periods, 2010-2039, 2040-2069 and 2070-2099, using 1980-2010 as the control period. Overall projected climate results reveal that temperature and precipitation are the most sensitiveparameters to the streamflow of Hunza River. MIROC-ESM predicted the highest increase in the future streamflow of the Hunza River due to increase in temperature and precipitation under RCP4.5 and 8.5 scenarios from 2010-2099 while predicted slight increase in the streamflow under RCP2.6 during the start and end of the 21 th century. However, BCCCSM1.1 predicted decrease in the streamflow under RCP8.5 due to decrease in temperature and precipitation from 2010-2099. However, Can ESM2 predicted 22%-88% increase in the streamflow under RCP4.5 from 2010-2099. The results of this study could be useful for decision making and effective future strategic plans for water management and their sustainability in the region.  相似文献   

7.
针对川中丘陵区紫色土坡耕地严重水土流失,选取典型代表李子溪流域为研究区,构建了其SWAT的模型数据库,包括地形、土壤、气象和土地利用数据库。并利用赵家祠水文站1970-1979年的实测径流和泥沙资料,对该流域的SWAT模型参数进行率定再采用1980-1986年的实测资料,对模型的适用性进行验证,同时用相对误差Re和Nash确定性系数Ens评价模拟效果。结果显示,径流和泥沙模拟相对误差均在±15%范围以内,Nash确定性系数均大于等于0.70,说明SWAT模型对李子溪流域年、月径流和年泥沙量的模拟精度较高。同时模拟值与实测值和降雨量的变化趋于一致。可见,用SWAT模型模拟和预测雨量较为丰沛、土壤侵蚀较严重的紫色丘陵地区的产流产沙是实用、可行的。  相似文献   

8.
Climate change has significantly affected hydrological processes and increased the frequency and severity of water shortage, droughts and floods in northeast China. A study has been conducted to quantify the influence of climate change on the hydrologic process in the Tao'er River Basin(TRB), one of the most prominent regions in northeast China for water contradiction. The Soil and Water Assessment Tool(SWAT) model was calibrated and validated with observed land use and hydro-climatic data and then employed for runoff simulations at upper, middle and lower reaches of the river basin for different climate change scenarios. The results showed that a gradual increase in temperature and decrease in annual precipitation in the basin was projected for the period 2020-2050 for both representative concentration pathways(RCP) 4.5 and 8.5 scenarios. The climate changes would cause a decrease in annual average runoff at basin outlet by 12 and 23 million m3 for RCP4.5 and 8.5, respectively. The future runoff in the upstream and midstream of the basin during 2020-2050 would be-10.8% and-12.1% lower than the observed runoff compared to the base period for RCP4.5, while those would be-5.3% and-10.7% lower for RCP8.5. The future runoff will decrease at three hydrology stations for the assumed future climate scenarios. The results can help us understand the future temperature and precipitation trends and the hydrological cycle process under different climate change scenarios, and provide the basis for the rational allocation and management of water resources under the influence of future climate change in the TRB.  相似文献   

9.
The relation between runoff and sediment and land cover is investigated in the Cedar Creek Watershed （CCW）, located in Northeastern Indiana, United States. The major land cover types in this watershed are cultivated land, woodland and pasture /Conservation Reserve Program （CRP）, which account for approximate 90 % of the total area in the region. Moreover, land use was changed tremendously from aooo to 9004, even without regarding the effect of the crop rotation system （corn ＆ soybean）. At least 49 % of land cover types were changed into other types in this period. The land cover types, ranking by changing area from high to low series, are rye, soybean, corn, woodland and pasture/CRP. The CCW is divided into 21 subwatersheds, and soil and water loss in each sub-watershed is computed by using Soil and Water Assessment Tool （SWAT）. The results indicate that the variations in runoff and sediment have positive relation to the area of crops （especially corn and soybean）; sediment is more sensitive to land cover changes than runoff; more heavy rainfall does not always mean more runoff because the combination of different land cover types always modify runoff coefficient; and rye, soybean and corn are the key land cover types, which affected the variation in runoff and sediment in the CCW.  相似文献   

10.
《山地科学学报》2020,17(3):624-640
Assessment of climate and land use changes impact including extreme events on the sediment yield is vital for water and power stressed countries. Mangla Reservoir is the second-largest reservoir in Pakistan, and its capacity is being reduced due to rapid sedimentation and will be threatened under climate and land use changes. This paper discusses the consequences of climate and land use change on sediment yield at Mangla Dam using General Circulation Models(GCMs), Land Change Modeler(LCM), Soil and Water Assessment Tool(SWAT) model after calibration and validation.Results show that over the historical period temperature is observed to increase by 0.10 o C/decade and forest cover is observed to reduce to the level of only 16% in 2007. Nevertheless, owing to the forest conservation policy, the forest cover raised back to 27% in 2012. Anticipated land use maps by using LCM of 2025, 2050 and 2100 showed that the forest cover will be 33%, 39.2%, and, 53.7%, respectively. All seven GCMs projected the increase in temperature and five GCMs projected an increase in precipitation,however, two GCMs projected a decrease in precipitation. Owing to climate change, land use change and combined impact of climate and land use change on annual sediment yield(2011-2100) may vary from-42.9% to 39.4%, 0% to-27.3% and,-73%to 39.4%, respectively. Under climate change scenarios projected sediment yield is mainly linked with extreme events and is expected to increase with the increase in extreme events. Under land use change scenarios projected sediment yield is mainly linked with the forest cover and is expected to decrease with the increase in forest cover. The results of this study are beneficial for planners, watershed managers and policymakers to mitigate the impacts of climate and land use changes to enhance reservoir life by reducing the sediment yield.  相似文献   

11.
In order to predict long-term flooding under extreme weather conditions in central Asia, an energy balance-based distributed snowmelt runoff model was developed and coupled with the Soil and Water Assessment Tool(SWAT) model. The model was tested at the Juntanghu watershed on the northern slope of the Tian Shan Mountains, Xinjiang,China. We compared the performances of temperature-index method and energy balanced method in SWAT model by taking Juntanghu river basin as an application example(as the simulation experiment was conducted in Juntanghu River, we call the energy balanced method as SWAT-JTH). The results suggest that the SWAT snowmelt model had overall Nash-Sutcliffe efficiency(NSE) coefficients ranging from 0.61 to 0.85 while the physical based approach had NSE coefficients ranging from 0.58 to0.69. Overall, on monthly scale, the SWAT model provides better results than that from the SWAT-JTH model. However, results generated from both methods seem to be fairly close at a daily scale. Thestructure of the temperature-index method is simple and produces reasonable simulation results if the parameters are well within empirical ranges. Although the data requirement for the energy balance method in current observation is difficult to meet and the existence of uncertainty is associated with the experimental approaches of physical processes, the SWAT-JTH model still produced a reasonably high NSE. We conclude that using temperature-index methods to simulate the snowmelt process is sufficient, but the energy balance-based model is still a good choice to simulate extreme weather conditions especially when the required data input for the model is acquired.  相似文献   

12.
The multi-model assessment of glaciohydrological regimes can enhance our understanding of glacier response to climate change. This improved knowledge can uplift our computing abilities to estimate the contributing components of the river discharge. This study examined and compared the hydrological responses in the glacier-dominated Shigar River basin(SRB) under various climatic scenarios using a semi-distributed Modified Positive Degree Day Model(MPDDM) and a distributed Glacio-hydrological Degree-day Model(GDM). Both glacio-hydrological models were calibrated and validated against the observed hydro-meteorological data from 1988-1992 and 1993-1997. Temperature and precipitation data from Shigar and Skardu meteorological stations were used along with field estimated degree-day factor, temperature, and precipitation gradients. The results from both models indicate that the snow and ice melt are vital contributors to sustain river flow in the catchment. However, MPDDM estimated 68% of rain and baseflow contribution to annual river runoff despite low precipitation during the summer monsoon, while GDM estimated 14% rain and baseflow contribution. Likewise, MPDDM calculated 32%, and GDM generated 86% of the annual river runoff from snow and ice melt. MPDDM simulated river discharge with 0.86 and 0.78 NSE for calibration and validation, respectively. Similarly, GDM simulated river discharge with improved accuracy of 0.87 for calibration and 0.84 NSE for the validation period. The snow and ice melt is significant in sustaining river flow in the SRB, and substantial changes in melt characteristics of snow and ice are expected to have severe consequences on seasonal water availability. Based on the sensitivity analysis, both models' outputs are highly sensitive to the variation in temperature. Furthermore, compared to MPDDM, GDM simulated considerable variation in the river discharge in climate scenarios, RCP4.5 and 8.5, mainly due to the higher sensitivity of GDM model outputs to temperature change. The integration of an updated melt module and two reservoir baseflow module in GDM is anticipated to advance the representation of hydrological components, unlike one reservoir baseflow module used separately in MPDDM. The restructured melt and baseflow modules in GDM have fundamentally enriched our perception of glacio-hydrological dynamics in the catchment.  相似文献   

13.
Interactions between surface water and groundwater are dynamic and complex in large endorheic river watersheds in Northwest China due to the influence of both irrigation practices and the local terrain. These interactions interchange numerous times throughout the middle reaches, making streamflow simulation a challenge in endorheic river watersheds. In this study, we modified the linear-reservoir groundwater module in SWAT (Soil and Water Assessment Tools, a widely used hydrological model) with a new nonlinear relationship to better represent groundwater processes; we then applied the original SWAT and modified SWAT to the Heihe River Watershed, the second largest endorheic river watershed in Northwest China, to simulate streamflow. After calibrating both the original SWAT model and the modified SWAT model, we analyzed model performance during two periods: an irrigation period and a non-irrigation period. Our results show that the modified SWAT model with the nonlinear groundwater module performed significantly better during both the irrigation and non-irrigation periods. Moreover, after comparing different runoff components simulated by the two models, the results show that, after the implementation of the new nonlinear groundwater module in SWAT, proportions of runoff components changed-and the groundwater flow had significantly increased, dominating the discharge season. Therefore, SWAT coupled with the non-linear groundwater module represents the complex hydrological process in the study area more realistically. Moreover, the results for various runoff components simulated by the modified SWAT models can be used to describe the hydrological characteristics of lowland areas. This indicates that the modified SWAT model is applicable to simulate complex hydrological process of arid endorheic rivers.  相似文献   

14.
As a major sediment area in the upper Yangtze River, Jialing River basin experienced substantial land-use changes, many water conservancy projects were constructed from the 1980 s onward to promote water and soil conservation. The water and sediment yield at the watershed outlet was strongly affected by these water conservation works, including ponds and reservoirs, which should be considered in the modelling. In this study, based on the observed data of the Weicheng River catchment, the relationships between precipitation, runoff, vegetation, topography and sediment yield were analyzed, a distributed runoff and sediment yield model(WSTD-SED) was developed, and the hydrological processes of different land-use scenarios were simulated by using the model. The main results are summarized as follows: 1) there is an alternating characteristic in river channels and reservoirs in the Jialing River hilly area, with scour occurring in wet years and deposit occurring in dry years. 2) Most of the sediment deposited in river channels and reservoirs is carried off by the largest flood in the year. 3) The model yielded plausible results for runoff and sediment yield dynamics without the need of calibration, and the WSTD-SED model could be usedto obtain qualitative estimates on the effects of land use change scenarios. 4) The modelling results suggest that a 10% increase in cropland(dry land) reforestation results in a 0.7% decrease in runoff and 1.5% decrease in sediment yield.  相似文献   

15.
Hydrological models within inflow forecasting systems for high-alpine hydropower reservoirs can provide valuable information as part of a decision support system for the improvement of hydropower production or flood retention. The information, especially concerning runoff, is however rarely available for the calibration of the hydrological models used. Therefore, a method is presented to derive local runoff from secondary information for the calibration of the model parameters of the rainfallrunoff model COSERO. Changes in water levels in reservoirs, reservoir outflows, discharge measurements at water intakes and in transport lines are thereby used to derive the local, “natural” flow for a given sub-catchment. The proposed method is applied within a research study for the ÖBB Infrastructure Railsystem division in the Stubache catchment in the central Austrian Alps. Here, the ÖBB operates the hydropower scheme “Kraftwerksgruppe Stubachtal”, which consists of 7 reservoirs and 4 hydropower stations. The hydrological model has been set up considering this human influences and the high natural heterogeneity in topography and land cover, including glaciers. Overall, the hydrological model performs mostly well for the catchment with highest NSE values of 0.78 for the calibration and 0.79 for the validation period, also considering the use of homogeneous parameter fields and the uncertainty of the derived local discharge values. The derived runoff data proved to be useful information for the model calibration. Further analysis, examining the water balance and its components as well as snow cover, showed satisfactory simulation results. In conclusion, a unique runoff dataset for a small scale high-alpine catchment has been created to establish a hydrological flow prediction model which in a further step can be used for improved and sustainable hydropower management.  相似文献   

16.
The Jianggang Harbour-centered radial sand ridge (RSR) is the largest sand body in the Yellow Sea. Its formation and evolution are of interest for scientists of various fields; however, the sediment provenance is uncertain. In this study, rare earth element (REE) geochemical compositions of the RSR sediments together with their potential sources are investigated to identify the provenance of the RSR sediments. The typical parameters ((La/Yb)N, (La/Sm)N and (Gd/Yb)N) as well as the upper continental crust-normalized patterns of REEs can only be associated with source rocks, and thus can be used as effective tracers for the origin and sources of sediments. However, the REE contents of sediments are affected by many factors, such as particle sorting and chemical weathering. Onshore RSR sediments are different in REE geochemical composition from offshore RSR sediments to some extent, suggesting that not all of the offshore RSR sediments have the same sources as the onshore RSR sediments. Meanwhile, the sediments adjacent to the northeast of Cheju Island and at Lian Island near the Lianyun Harbour were not the source of the RSR sediments due to their distinctive REE patterns, δEu, (La/Yb)N, (Gd/Yb)N and (La/Sm)N. The Korean river sediments could be dispersed to the Jiangsu Coast slightly impacting the fine fractions of the RSR sediments, particularly the offshore RSR sediments. Additionally, geochemical comparisons show that the modern Yellow River was responsible for the onshore RSR sediments, whereas the sediment loads from the Yangtze River could serve as a major contributor to the RSR, particularly the offshore RSR. In addition, the offshore RSR could also be partly fed by an unknown source due to some high values of (La/Yb)N, (La/Sm)N and La contents differing from those of the Chinese and Korean river sediments.  相似文献   

17.
Post-fire field measurements of sediment and run off yield were undertaken in natural rainfall event-basis during five rainy months in Korea on a total of 15 small plots: four replica burned unseeded plots, six replica burned seeded plots, and five replica unburned plots. The main aim was to evaluate the effects of vegetation recovery and spatial distribution patterns on sediment and runoff response between and within the treatment replica erosion plots. Six-years after the wildfire, total sediment and runoff yield in the burned unseeded plots with 20%-30% vegetation cover was still 120.8 and 20.6 times higher than in the unburned treatment plots with 100% ground cover, 8.3 and 6.7 times higher than in the burned seeded plots with 70%-80% vegetation cover, while only 1.6 and 2.0 times higher than in the burned seeded plots with 50%-60% vegetation cover, respectively. The differences in sediment and runoff yield between the treatment plots was proportional to total vegetation cover, distance of bare soil to vegetation cover, magnitude of rainfall characteristics and changes in soil properties, but not slope gradient. Three out of the six within-treatment pairs of two replica plots showed large differences in sediment and runoff yield of up to 6.0 and 4.2 times and mean CV of up to 99.1% and 62.2%, respectively. This was due to differences in the spatial distribution patterns of surface cover features, including aggregation of vegetation and litter covers, the distance of bare soil exposed to vegetation cover closer to the plot sediment collector and micro topographic mounds and sinks between pairs of replica plots. Small differences in sediment and runoff of only 0.9-1.4 folds and mean CV of 8.6%-25% were observed where the within-treatment pairs of replica plots had similar slope, total surface cover components and comparable spatial distribution pattern of vegetation and bare soil exposed surface covers. The results indicated that post-fire hillslopes undergoing effective vegetation recovery have the potential to reduce sediment and runoff production nearer to unburned levels within 6-years after burning while wildfire impacts could last more than 6-years on burned unseeded ridge slopes undergoing slow vegetation recovery.  相似文献   

18.
Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier, Himachal Pradesh, India for different melt seasons during the period 2011-2014. Maximum suspended sediment concentration in the meltwater was found during the month of July 2011, 2012 and 2014 constituting to 55.2%, 48.3% and 46.9%, respectively. Whereas in 2013, maximum suspended sediment concentration was observed in August accounting for 46.1% of the total. On the other hand, maximum suspended sediment load was monitored in the month of July 2011, 2012 and 2014 constituting 59.5%, 63% and 55.7% of the total, respectively. Whereas in 2013, maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load. Annual distribution of suspended sediment concentration (SSC) and suspended sediment load (SSL) in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013, which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods. Marked diurnal variation has been observed in the SSC of meltwater. Strong correlation was observed between SSC and SSL with discharge. On the other hand, SSC and SSL also showed strong exponential correlation with air temperature of the studied area. Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season (July and August) and low during the late melt season (September and October). The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1 mm/yr, which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot, Chorabari and Gangotri glaciers, which may be caused by its geological setting containing high erosion resistant rocks such as granite, granite gneiss and porphyritic granite.  相似文献   

19.
There is a consensus that sediment delivery ratio in the Chinese Loess Plateau is close to 1at the inter-annual timescale. However, little information is available about the sediment delivery at finer timescales. We evaluated the sediment delivery from plots to watersheds at the event or intra-annual, annual, and inter-annual timescales within the Wudinghe river basin, a 30,261 km2 basin in the Loess Plateau. We calculated the ratio of sediment output to sediment input and presented the temporal change of the channel morphology to determine whether sediment deposition occurs.Although a single flood event frequently has a sediment yield exceeding 10,000 t km-2, sediment deposition rarely occurs except during some small runoff events(sediment yield 5000 t km-2) or dry years(sediment yield 10,000 t km-2) when moving from slopes up to the main channels of the Wudinghe River. This observation suggests a sediment delivery ratio close to 1 even at the event or intra-annual and the annual timescales, but not necessarily at the interannual timescale. Such a high sediment delivery ratio can be related to hyper-concentrated flows, which have very strong sediment transport capacity even at low flow strength. Because hyper-concentrated flows are well-developed in the whole Loess Plateau, a sediment delivery ratio close to 1 below the interannual timescale possibly remains true for other rivers in the Loess Plateau.  相似文献   

20.
1　Introduction　Manhasmodifiedmanyoftheworld’scoastlines ,eitherdirectlybyconstructionordredging ,orindi rectlyasaresultofenvironmentalchangesthatinflu encesedimentsupply ,runoff,orclimate (Johns ,1995 ) .HumanactivityhasalsoproducedthemostprofoundeffectsonthecoastalenvironmentinChina .Forex ample,damconstructions ,whichrestrictpeakflowsintheupstreamoftheYellowRiver ,couldgreatlyre ducethenaturalsupplyofsedimentintotherivermouthandresultintheerosionofbeaches .　Inrecentyears,manystudiescon…  相似文献   

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